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LI-6262 CO2/H2O Analyzer Operating and Service Manual

1. Orient the scrubber tube so that the soda lime is on the bottom and the magnesium perchlorate is on the top Attach the bottom hose nearest the soda lime to the FROM CHOPPER fitting An auxiliary pump should be placed between the FROM CHOPPER fitting and the bottom hose of the scrubber tube Make sure the pump is oriented to pump in the direction indicated in Figure 2 3 Attach the top hose nearest the perchlorate to the REFERENCE IN fitting Attach a jumper hose between the REFERENCE OUT and TO CHOPPER fittings Setup amp Operation 2 7 Section 2 REFERENCE ea T IN CHOPPER FROM e CHOPPER SAMPLE REFERENCE OUT OUT soal Figure 2 3 Hose connections for operation in absolute mode 2 8 Setup amp Operation D Theory of w Operation 3 1 General Description The LI 6262 is a differential non dispersive infrared NDIR gas analyzer The CO and H2O measurements are based on the difference in absorption of infrared IR radiation passing through two gas sampling cells The reference cell is used for a gas of known CO or H20 concentration and the sample cell is used for a gas of unknown concentration Infrared radiation is transmitted through both cell paths and the output of the analyzer is proportional to the difference in absorption between the two Thermoelectric Cooler Lens k Motor 7 N Fa Sample f Referen an Z eference 3 Source Feedback Photodiode Chopping Shutter
2. System Software 5 19 FCT 20 29 20 CO 20 CO2 Enters menu at function 20 se eon 21 29 CO Channel Codes Press FCT followed by the appropriate code to view the CO channel codes These channels can only be viewed by pressing FCT they are not executable from the main menu NOTE CO reference value may be entered via the keyboard as a constant FCT 59 or entered via analog signal See Section 6 4 Code Description 21 CO mV non linear 22 CO mol mol absolute 23 CO mol mol differential 24 CO Pa absolute 25 CO gt Pa differential 26 CO gt ug g absolute 27 CO ug g differential 29 CO mol mol reference 5 20 System Software FCT 30 39 30 H 0 30 H20 Enters menu at function 30 Tada 31 39 H20 Channel Codes Press FCT followed by the appropriate code to view the HO channel codes These channels can only be viewed by pressing FCT they are not executable from the main menu Code Description 31 H20 mV non linear 32 H20 mmol mol absolute 33 H20 mmol mol differential 34 H20 kPa absolute 35 H20 kPa differential 36 H20 mg g absolute 37 H20 mg g differential 38 H20 Dewpoint 39 H20 mmol mol reference NOTE H30 reference value may be entered via the keyboard as a constant FCT 68 or entered via analog signal see Section 6 4 System Software 5 21 FCT 40 45 40 Miscellaneous 40 MISC Enters menu at function 40 T4 41 44 Temperature and Auxiliary
3. return mv static double cal_slope double mv returns the slope of the cal function return A_cal 2 B_cal 3 C_cal 4 D_cal 5 E_cal mv mv mv mv static double chi double mfw Sample Program H 3 Eqn 3 21 LI 6262 manual or 6 5 LI 6251 or LI 6252 manual return 1 Water_A 1 mfw static double p0_over_p double kPa if water_flag return 101 3 kPa 0 88451 0 10889 The LI 6262 approx return pow 101 3 kPa 0 9 else return 101 3 kPa double compute_co2 double Cal_temp double Cal_k double coeffs double mv double temp double ref double pressure double vap_ref double vap_samp double water_corr_a int vapor_correct_flag Compute co2 concentration umol mol Cal_temp calibration temp C Cal_k calibration K factor coeffs Calibration A B C D and E mv raw CO2 signal mV temp IRGA temp C ref Co2 reference concentration umol mol vap_ref Vapor concentration mmol mol of reference side vap_samp Vapor concentration umol mol of sample side water_corr_a A value for water correction vapor_correct_flag 0 no vapor corrections 1 band broadening only 2 band broadening and dilution based on ref Returns CO2 concentration in umol mol double Cs H 4 Sample Program water_flag 0 T_cal Cal_temp K_cal Cal_k A_cal coeffs 0 B_cal coeffs 1 C_cal coeffs 2 D_cal coeffs 3 E_cal coeffs 4
4. Setup amp Operation This section will describe the steps necessary for you to set up the hardware and software in your LI 6262 to begin making measurements Follow these steps to configure your analyzer where noted the steps are described in more detail in this and other sections 2 1 Setup and Operation 1 Install Gelman filters The Gelman filters are used externally and must be inserted in the Sample and Reference airstreams upstream from the analyzer See Section 2 3 Gelman Filter Installation below Prepare a soda lime desiccant tube as described in Section 7 4 and attach to the SCRUBBER holder on the back panel Absolute or Differential mode operation The LI 6262 can be operated in absolute or differential mode In absolute mode the reference cell contains a zero concentration of CO and H2O The sample cell is connected to the unknown gas to be measured The signal from the sample cell is compared to the zero gas reference signal to provide absolute measurements of CO and H O In differential mode the reference cell contains a non zero gas of known concentration The difference between absorption in the sample cell and in the reference cell is measured Configuring the LI 6262 for differential or absolute mode operation requires slightly different hose connections see Absolute vs Differential Mode Operation below Turn the power ON The LI 6262 can be operated with AC or DC power See Section 2 2 Power On
5. H20 Detector H20 Filter Thermoelectric Cooler Lens Dichroic Beam CO Filter COz Detector Splitter The infrared source is vacuum sealed for long life gt 10 000 hours and high stability A separate optical feedback circuit with a photodiode maintains the source at a constant color temperature 1250 K A gold reflector surrounding the IR source maximizes the radiation output from the source and decreases the power required The chopping shutter disc is spun by a motor whose shaft turns on high precision bearings for long life and low noise Rotation is precisely controlled at 500 hertz on a phase locked loop circuit The optical path between the source and optical bench is sealed and continuously purged of CO and H20 by an attached tube containing soda lime and magnesium perchlorate This eliminates interference due to ambient CO or H20 vapor Theory of Operation 3 1 Section 3 The sample cells are gold plated to enhance IR reflection and resist tarnishing over time One set of sample cells is used for both HzO and CO measurements by using a dichroic beam splitter to provide radiation to two separate detectors A 150 nm bandpass optical filter is used to tune the CO detector to the 4 26 micron absorption band for CO and a 50 nm bandpass optical filter tunes the H2O detector to the 2 59 micron absorption band Both filters provide excellent rejection of IR radia
6. N Beenaa ak a oY OA O annann DAC1 5V DAC1 100mV DAC1 20mA SIG GND DAC2 5V DAC2 100mV DAC2 20mA SIG GND CO 0 1S CO 1S HO 0 1S HzO 1S TEMP 5V SIG GND AUX CHASSIS GND Figure 6 3 Connection of data logger for non linear output 6 12 Interfacing Section 6 6 4 Auxiliary Channel Inputs Terminal 15 is connected to the auxiliary channel which may be used to input an analog signal from a user supplied external sensor CO and H2O references may be input through this channel as well as barometric pressure Use FCT 73 to designate which channel 29 39 or 43 the analog signal will be sent to Figure 6 4 shows how to connect a sensor to the terminal strip on the back panel of the LI 6262 NOTE If the 6262 03 Pressure Transducer is installed in your analyzer the auxiliary channel input is no longer available the raw mV reading from the transducer can be measured at this terminal however Please see Section 6 6 for a complete discussion of the 6262 03 Connect the positive input from the sensor to the terminal labeled AUX Connect the negative input to the terminal labeled SIG GND The auxiliary channel has an input voltage range of 4 096V DAC1 5V DAC1 100mV DAC1 20mA SIG GND DAC2 5V DAC2 100mv DAC2 20mA SIG GND CO 0 18 CO 1S H20 0 18 H2O 1S TEMP 5V SIG GND AUX CHASSIS GND EXTERNAL SENSOR nannnnnannnnnnnn CAE t
7. The response curve for the pressure sensor is given by the equation Y A BX CX where Y is the sensor output in kPa X is the mV output of the sensor A is the Y axis intercept and B is the calibration multiplier which is equal to the slope of the line representing the sensor s response Figure 6 7 On the 6262 03 calibration sheet the offset A is given as FCT 71 and the multiplier B is given as FCT 72 Enter these values into the software at FCT 71 Aux A and FCT 72 Aux B Make sure that FCT 75 Aux C is set to zero These values convert the mV output of the pressure transducer to pressure in units of kPa Y Slope B AL 0 X Figure 6 7 Response curve for pressure sensor Example On the 6262 03 calibration sheet the values listed are as follows FCT 71 58 239 FCT 72 0 01510 FCT 73 43 FCT75 0 Enter the above values into software 6 16 Interfacing Section 6 Pons ae RETTA NEW no 51 5 FCT 73 ee on FCT 75 ee ae Wo You can view the pressure value at FCT 43 and mV output at FCT 44 Both of these values can be viewed on a custom display or sent via the RS 232C output to a printer and or computer terminal Interfacing 6 17 7 1 Recharging the 6000B and 6200B Batteries Batteries should be fully recharged as soon as possible after use Long term storage in a discharged state can reduce the battery s capacity especially at high temperatures Battery charging circuitry for the 6000B and
8. Toll free 800 345 2100 Toll free FAX 800 345 5232 Soda Lime Part 66352 Me C104 2 Part 49001 500g lt 8 water Soda Lime Part S201 212 LI COR Part 9960 071 Mg C104 2 Part M54 500 500g Soda Lime Part C703 B76 Mg ClO4 2 Part C260 M61 Dehydrite 500g Suppliers B 1 Function Code 00 01 02 03 04 05 06 07 08 09 Software Commands Description Page SETUP 5 3 Set CO Calibration 5 4 Set H20 Calibration 5 5 Set Miscellaneous 5 5 Set Displays 5 6 Set D A Conversion 1 5 7 Set D A Conversion 2 5 7 Backlight ON OFF 5 8 Test Menu 5 8 Integrate 5 11 PRINT 5 13 Print Header 5 14 Print Data 5 14 Set Print List 5 14 Auto Print 5 15 Auto Header 5 15 Print Calibration Data 5 16 Set RS 232C Port 5 17 Reset Timer 5 18 Full Status 5 18 CO2 5 20 CO raw mV 5 20 CO mol mol absolute 5 20 CO umol mol differential 5 20 CO Pa absolute 5 20 CO Pa differential 5 20 CO ug g absolute 5 20 CO ug g differential 5 20 CO mol mol reference 5 20 Software Commands C 1 Function Code 30 31 32 33 34 35 36 37 38 39 C 2 Software Commands Description H20 raw mV H20 mmol mol absolute H20 mmol mol differential H20 kPa absolute H20 kPa differential H20 mg g absolute H20 mg g differential H20 dewpoint C H20 mmol mol reference MISCELLANEOUS Temperature mV Temperature C Pressure kPa Auxiliary mV Timer Integration A Integration peak valu
9. Water_A water_corr_a if vapor_correct_flag 0 vap_ref 0 vap_samp 0 Cs ppm mv ref temp vap_ref 1000 0 pressure vap_samp 1000 0 pressure pressure The dilution correction is hypothetical It says what the concentration in the sample cell would be if the water vapor concentration there were the same as in the reference cell if vapor_correct_flag 2 Cs 1 0 vap_ref 1000 0 1 0 vap_samp 1000 0 return Cs double compute_h2o double Cal_temp double Cal_k double coeffs double mv double temp double ref double pressure Compute co2 concentration umol mol Cal_temp calibration temp C Cal_k calibration K factor coeffs Calibration A B C mv raw H20 signal mV temp IRGA temp C ref H20 reference concentration umol mol Sample Program H 5 Returns water vapor concentration in mmol mol xJ double Ws water_flag 1 T_cal Cal_temp K_cal Cal_k A_cal coeffs 0 B_cal coeffs 1 C_cal coeffs 2 D_cal 0 E_cal 0 Ws ppm mv ref temp 0 0 pressure return Ws double dewpoint double vp_kPa double z z log10 vp_kPa 61083 return 242 62 z 7 6448 2 alae teak tan eee eee cat A AE DA a AENA AEEA IN PEN ET H 6 Sample Program
10. A quick reference card for entering console commands via the LI 6262 keypad or from an external terminal Spare Parts Kit This kit contains replacement parts for your LI 6262 As you become familiar with the analyzer you will learn which items to keep close at hand and which items can be stored away External Scrubber and Desiccant Tube This tube is used during normal operation Several spare gaskets and adhesive disks have been included for future use 1000 90 Data Communications and Utility Software This software can be used to communicate with an IBM PC XT AT PS2 or compatible The software is provided on 3 1 2 inch diskettes RS 232C Cable Part 392 02874 DTE to DCE used to connect the LI 6262 DCE to a DTE device such as an RS 232C printer RS 232C Gender Changer Part 392 02977 Female to female gender changer used to connect the RS 232C cable to most computers Unpacking amp Inspection 1 1 Section 1 There are several optional accessories available for use with the LI 6262 including 6262 03 Pressure Transducer measures pressure in the sample optical cell and its millivolt signal is used by the LI 6262 analyzer software to calculate pressure values CO and H20 readings are then automatically corrected by the software for any detected pressure changes 6262 04 Reference Pump designed to purge the reference cell of H2O during absolute mode operation Air flow created by movement of the chopping shutt
11. FCT 15 The column header interval is the number of data lines which will be printed between column headers See Section 5 FCT 15 Setup amp Operation 9 Section 2 Set the displays FCT 91 99 The LCD display has two lines and each line can be configured to show any channel code 21 29 CO2 31 39 H20 or 41 47 MISC As many as nine two line display configurations can be defined by the Set Displays routine Each display is identified by a number through 9 and can be viewed by pressing the appropriate number without pressing FCT See Section 5 FCT 04 Begin making measurements 2 2 Power On 1 If a LI COR rechargeable battery is being used connect it to the 10 5 16VDC battery connector on the rear panel The 6000B Rechargeable Battery will provide power for approximately 3 2 hours at 25 C or 2 4 hours at 40 C The 6200B Rechargeable Battery has twice the capacity of the 6000B Instructions for recharging these batteries are given in Section 7 1 One set of battery leads with a 3 pin plug is included in your spare parts kit for connection to a user supplied battery 10 5 16VDC 1 5 amp maximum current required or other DC power supply If AC line voltage is being used make sure the AC VOLTAGE selector on the back panel is set correctly choose the 115 setting for 100 130VAC or the 220 setting for 200 260VAC and plug the line cord into the receptacle on the back panel Turn the power switch on
12. FCT 50 59 50 CO Calibration 50 CO2 CAL Enters menu at function 50 Talbi 51 59 CO Calibration Stack The CO calibration stack FCT 51 57 contains individual CO calibration coefficients as well as the prompt to enter the CO reference in ymol mol FCT 59 Enter CO2 reference in mmol mol Code Prompt Description 51 C2 T Calibration Temperature 52 C2 K Calibration Constant K 53 C2 A Calibration Coefficient A 54 C2 B Calibration Coefficient B 55 C2 C Calibration Coefficient C 56 C2 D Calibration Coefficient D 57 C2 E Calibration Coefficient E 59 C2 R CO Reference umol mol The CO reference value FCT 59 should reflect the dilution by water vapor if the reference is not dry For example if the reference gas contains 300 mol mol CO when dry and 0 5 kPa of water vapor is added before it enters the reference cell then C2 R 300 1 0 5 P where P is the local barometric pressure 5 24 System Software FCT 60 68 60 H O Calibration 60 H20 CAL Enters menu at function 60 se ee 61 68 H O Calibration Stack The H20 Calibration stack FCT 61 68 contains individual H2O calibration coefficients as well as the prompt to enter the H20 reference FCT 68 Enter H2O reference in mmol mol Code Prompt Description 61 H2 T Calibration Temperature 62 H2 K Calibration Constant K 63 H2 A Calibration Coefficient A 64 H2 B Calibration Coefficient B 65 H2 C Calibration Coefficient C 6
13. as you will likely have different pressures Instead split the flow upstream of the analyzer and run separate hoses to the reference and sample cells Also be sure the flow rates through both sides are the same The concentrations used to set the zero and span should bracket the range of concentrations expected in subsequent measurements For example using 340 ppm for the zero and 300 ppm for the span might be the proper selections for flow thru photosynthesis applications where drawdowns from ambient are expected There is generally a small zero shift when the reference concentration changes Therefore if operating in a mode in which there are significant changes in reference gas concentration you should re zero the analyzer following each change in concentration CO2 Zero and Span Calibration Set the CO reference to zero FCT 59 If you are not using the 6262 03 Pressure Transducer enter the barometric pressure in FCT 77 2 Display absolute CO umol mol FCT 22 3 Flow a dry CO gt free gas through both sides of the analyzer 4 Unlock the CO zero potentiometer and adjust until the absolute CO concentration on the display reads zero 5 With the CO gt free gas on the reference side flow a span gas through the sample cell Set the span potentiometer to read the span gas mole fraction umol mol 6 Flow the span gas through both cells of the analyzer at the same flow rate The flow rate should match that used in the ref
14. pressure 101 3 kPa T is IRGA temperature C or K and T is IRGA calibration temperature C or K The situation is a little more complicated in differential mode If we place a nonzero CO mole fraction in the reference cell then infrared radiation will be absorbed transmittance will decrease and v should decline This decline is prevented however by an automatic gain control circuit that increases the detector gain by an amount necessary to hold v constant This provides span stability over the long term but the ouput voltage must now be corrected for the gain increase before the calibration polynomial can be applied How much is this gain increase The detector output signal v is proportional to photon flux so to hold v constant the gain must be inversely proportional to the reduced photon flux that results when CO3 is added to the reference cell Transmittance is proportional to the photon flux so the gain increase is proportional to 1I t where the subscript r refers to the transmittance of the reference cell Therefore to correct for the gain increase we find the transmittance of the reference cell given the reference cell CO mole fraction and multiply the analyzer output voltage by T To find T we assume that the sample and reference cells are optically identical when they contain the same absorbing gas concentrations If the 3 4 Theory of Operation Section 3 two cells are identical then for a given gas
15. 22 29 32 39 11 Print Header 11 prints header 12 Print Data 12 prints data 13 Set Print List 13x x X X X X X X X X x is any channel code 21 29 31 39 41 47 14 Auto Print 14x prints a line of data every x seconds where x is any number 0 2 0 5 or 1 to 3600 15 Auto Header 15x prints a column header every x lines of data from 1 to 999 16 Print Calibration Data 16 prints calibration stack for H2O amp CO 18 Reset Timer 18 resets the timer to zero 19 Full Status 19x x is optional parameter to output 46 Integration A 46 47 Integration Peak Value 47 49 Software Revision I D 49 71 Auxiliary A 71 lt A gt A is the auxiliary A value 72 Auxiliary B 72 lt B gt B is the auxiliary B value 73 Auxiliary Destination 73x x is auxiliary destination channel lt null gt 29 39 or 43 74 Set Average Time 74x x is any value from 0 to 30 75 Auxiliary C 75 lt C gt C is auxiliary C value 76 Vapor Flag 76x x is 0 1 or 2 to turn ON OFF vapor dilution corrections 77 Pressure 77x x is barometric pressure in kPa 78 H20 Cal a 78x x is vapor correction a 91 Display 1 91x x x is channel code 21 27 29 31 39 41 44 for top and bottom line 99 Display 9 91 99 are all the same Console Commands E 3 B Saturation Vapor Pressure Table SCIADNEWNKO SSOPNNEMUAABSNISNHNAS DBaORHDHDORHHNANNEAINA This table gives the saturation vapor pressure
16. Integration A 47 Integration peak value 49 Software Revision ID Console Commands E 1 Calibration and Configuration Stacks 50 CO2 CAL 51 CO Calibration T 52 CO Calibration K 53 CO gt Calibration A 54 CO Calibration B 55 CO Calibration C 60 H20 CAL 61 H20 Calibration T 62 H O Calibration K 63 H20 Calibration A 64 H O Calibration B 65 H20 Calibration C 56 CO Calibration D 57 CO Calibration E 59 CO reference umol mol 68 H20 reference mmol mol Calibration and Configuration Stacks 70 MISC 71 Auxiliary A 72 Auxiliary B 73 Auxiliary Destination 74 Average Time 75 Auxiliary C 76 Vapor Flag 77 Pressure 80 DAC 81 D A Conv Code 1 82 D A Conv 1 Min 83 D A Conv 1 Max 84 D A Conv Code 2 85 D A Conve 2 Min 86 D A Conv 2 Max 90 DISP 91 Display 1 92 Display 2 93 Display 3 94 Display 4 95 Display 5 96 Display 6 97 Display 7 98 Display 8 99 Display 9 78 Vapor Correction a E 2 Console Commands Remote Commands Function Type the following on a computer or terminal comments 01 Set CO Calibration 01T K A B C D E REF VAPOR FLAG 02 Set H20 Calibration 02T K A B C REF 05 Set D A Conversion Code 1 05x low high x is channel code 22 27 32 38 42 06 Set D A Conversion Code 2 06x low high same as 05 07 Backlight 07Y Yes or 07N No to turn backlight ON OFF 09 Integrate 09x start start value stop stop value x is channel code
17. J x w To 273 Py G 1 3 30 K convo SEY T4273 X W P JT 273 AC C C The water correction is based upon a theoretically justifiable procedure which requires determination of a single physically meaningful constant and can be applied to any LI COR 6200 series infrared gas analyzer and perhaps others as well 3 6 Dilution Corrections A dilution correction can be applied in the LI 6262 if desired When one component gas of multicomponent mixture is decreased at constant pressure the partial pressures of all other components are increased accordingly For example if water vapor is removed at constant pressure then the partial pressures of other components increase according to p Pt 3 31 1 w 1000 where w is the water vapor mole fraction mmol mol and the pW t are 1 partial pressures of other component gases before water vapor was removed For individual components Equation 3 31 becomes wet p Pi _ 3 32 1 w 1000 Theory of Operation 3 11 Section 3 It is often necessary to correct the CO mole fraction for differences in water vapor mole fraction in sample and reference cells when CO and water vapor are measured together An apparent CO mole fraction difference will develop if water vapor is added to or removed from either air stream whether a net CO flux is present or not This dilution effect can be removed when the Vapor Flag FCT 76 is set to BndBrd Dil Ref the CO mole frac
18. LI 6262 directly as an analog 1 2 Unpacking amp Inspection Section 1 signal Analog output is linear and the 0 50 C dew point range is scaled over 0 5 volts 100mV C LI 670 Flow Control Unit The LI 670 is a valuable accessory for use with the LI 6262 which can be used for a variety of calibration and gas exchange measurement functions In its simplest form the LI 670 is used as a constant source of air flow to the LI 6262 Independent pumps and rotameters allow variable flow rates through the LI 6262 sample and reference cells if desired For calibration of the LI 6262 soda lime and desiccant tubes provide a zero gas source a span gas can be swapped between cells to adjust for any zero offset present during calibration The LI 670 also can be used as a power source for the LI 6262 a built in low battery detection circuit monitors battery life of the system Mounting brackets are included for attaching the LI 670 and LI 6262 making the system completely portable 1 2 Checking the Batteries If purchased Batteries are tested and fully charged when they leave the factory but they may discharge during shipping It is a good idea to test each battery to see if it is charged If the batteries are below 12V they should be charged before use Refer to Section 7 1 for charging instructions NOTE Never store batteries in a discharged state Charge stored bat teries every 3 months Unpacking amp Inspection 1 3
19. Press FCT followed by the appropriate code to view the temperature and auxiliary channel codes These channels can only be viewed by pressing FCT they are not executable from the main menu Code Description 41 Temperature mV 42 Temperature C 43 Pressure kPa 44 Auxiliary mV NOTE Pressure kPa FCT 43 is used for computations This comes from FCT 77 or an analog signal at FCT 44 see Section 6 4 45 Timer Displays accumulated time in seconds from instrument start up Timer 3 7 The Timer acts as a counter which accumulates the number of seconds since instrument start up to 999 999 or since the Reset Timer function FCT 18 was last executed The Timer can also be viewed by entering 45 into any of displays 1 to 9 FCT 91 99 The Timer function can be output to a computer or printer by entering 45 into the Set Print List function FCT 13 5 22 System Software FCT 46 49 46 Integration A During the integration FCT 09 channel 46 shows the total area A under the peak from the last integration or the accumulating area during the present integration 47 Integration Peak Value Displays the peak value of the target channel obtained during the last integration or the largest value so far during the present integration iil 47 49 Software Revision I D Software revision number Press RevID 2 02 FCT to escape System Software 5 23
20. RS 232C port Follow the instructions included with the 1000 90 to load the COMM program The 1000 90 instructions describe how to run the COMM program using the softkeys F1 thru F9 Here are some tips for using the program with the LI 6262 F1 Accesses the configuration menu Select the configuration labeled General Purpose by pressing ENTER F2 Change COM Notice that pressing F2 will toggle between COMI and COM2 on the screen menu Use this to select the communications port which is connected to the computer if different than the default setting F3 Local echo ON or OFF Toggles between ON and OFF Having the echo ON is useful to view the characters on the CRT which are typed if a computer is used to backload remote commands to the LI 6262 F6 File Specifies the file into which incoming data will be copied if desired Specify both the filename and the path where you want to copy the data file For example typing C DATA will create an ASCII file named DATA on the root directory of drive C Further manipulation of the data file can be accomplished with any software program that can read data from a generic text file There are several other inexpensive communication programs which may be used to interface the LI 6262 to a computer Two such programs for IBM PC s and compatibles are PC TALK Freeware P O Box 862 Tiburon CA 93920 and ProComm Data Storm Technologies Inc P O Box 1471 Columbia MO 65205 Either of
21. Thus if other atmospheric components are constant an equivalent pressure can be defined as Pe agPg awe P agXq AawXw 3 19 where Py is the total pressure of dry air and ag is a dry air weighting factor LI COR calibrates all of its analyzers using CO or water vapor in air so aq 1 is taken as the standard condition Substituting equation 3 18 into equation 3 19 gives Pe P 1 aw 1 X 3 20 The value of aw is not an intrinsic constant comparable to other such values in the literature because it uses dry air as a reference instead of nitrogen Its value has been empirically determined to be about 1 5 against dry air The value of ay used in 3 20 is entered into the LI 6262 using FCT 78 Equation 3 20 can be extended to include nitrogen as standard and both water vapor and oxygen or other gases as variable components P can be written in a more general form to anticipate that possibility Pe P 1 ay 1 Xy Xb 1 X i 3 21 For the present equation 3 20 is implemented in the LI 6262 software equation 3 21 has not yet been tested Equation 3 20 can be compactly rewritten as Pe PxX XK 3 22 where X 1 ay 1 X and then incorporated into the CO calibration function The form of the CO calibration function equation 3 4 was derived empirically but it can also be derived from a scaling law called the non overlapping line approximation which holds when absorber concentrations are low
22. below Calibrate the analyzer as described in Section 4 Setup amp Operation 2 1 Section 2 2 2 Connect sample airstream to be measured Configure analyzer for data output Data can be obtained from the LI 6262 in several different ways from the display via RS 232C output or from one of the analog output channels See Section 6 Interfacing for more information Configure the software All software commands are executed by pressing FUNCTION and then entering a two digit function code Some codes execute a function directly while others access scrollable lists of options or other functions Items in lists can be selected by scrolling the list with the arrow keys and pressing ENTER Enter the station barometric pressure Press FCT followed by 77 and enter the barometric pressure in kPa Pressure may also be input continuously using the 6262 03 Pressure Transducer from LI COR or through auxiliary channel 15 with an external pressure sensor as described in section 6 4 Set the parameters for RS 232C output if necessary Press FCT followed by 17 and enter the data output parameters Set the Print List FCT 13 Data from up to ten different channels may be sent to the RS 232C port at a specified interval See Section 5 FCT 13 Set Auto Print FCT 14 Enter specified interval in seconds 0 1 3600 at which to transmit data defined at FCT 13 to the RS 232C port See Section 5 FCT 14 Set Auto Header
23. concentration the transmittance will be the same whether it is computed against zero between the cells or within either cell Now suppose the reference cell contains CO mole fraction C If we can compute what the transmittance would be if C were in the sample cell against zero in the reference cell then we will know what the transmittance actually is in the reference cell when it contains C and that will tell us how to correct for the gain change The strategy for accomplishing this is straightforward First we use C to solve equation 3 4 for V giving v t i Then rearrange equation 3 2b to find T given V A 1 42 3 6 Equations 3 5 and 3 6 ordinarily apply to the situation where C is in the sample cell and zero is in the reference cell but if the cells are identical T also computes the transmittance in the reference cell when C is present The gain correction G equals T as shown earlier so g 1 7 3 7 After correcting the differential voltage V for the gain change we can write GV V V Solving for V and substituting the result into equation 3 4 gives the general expression for computing the gas concentration C in the sample cell given concentration C in the reference cell C H vo vo 2 3 8 0 The differential CO mole fraction AC is simply C C AC F vo vo 2 C 3 9 o Theory of Operation 3 5 Section 3 In this section we have assumed that the sample and reference cells are
24. exact CO mole fraction of which is not known One could scrub the reference cell and measure the incoming CO concentration in absolute mode However there will be a small zero shift when the reference gas is reduced from around 350 ppm to 0 ppm so a zero adjustment must be made each 3 12 Theory of Operation Section 3 time the reference cell is scrubbed The same is true when ambient air is returned to the reference cell It is easier to leave the reference gas alone and scrub the sample cell this avoids zero shifts and gain changes One can then measure the output voltage V and compute V and C according to equations 3 34 and 3 35 Ve 3 34 d rv P T 273 ae P To 273 These values can be used as needed to compute C or AC over as long a time period as C and temperature are stable Note This is not implemented in the instrument but is provided as an aid to those needing this trick Theory of Operation 3 13 Section 3 3 14 References Goff J A and S Gratch 1946 Trans Amer Soc Heat and Vent Eng Vol 52 p 95 Jamieson J A et al 1963 Infrared Physics and Engineering McGraw Hill New York N Y p 65 List R J 1966 Smithsonian Meteorological Tables 6th rev ed The Smithsonian Institution 527 pp Wolfe W L and G J Zissis 1978 The Infrared Handbook Office of Naval Research Department of the Navy Washington D C Theory of Operation VA Calibration 4 1 Calibrati
25. flow Conc without flow When setting the span multiply the reading obtained without flow by the correction factor and set the displayed concentration equal to the corrected value This flow concentration relationship is linear over the entire measurement range of the LI 6262 If another flow rate is used a new correction will have to be calculated 4 6 Setting the Zero and Span in Software FCT 08 Test Menu contains CO and H2O Zero Span functions that provide a software method of setting the zero and span without manually adjusting the potentiometers There are two advantages of allowing software zero and span adjustments the zero and span can be set using a remote Calibration 4 9 Section 4 command sequence and the user can get the analyzer back on scale through software if the zero and or span has gone beyond the range of the potentiometer The zero and span parameters initially default to these values H2 Zero 0 0 mV offset H2 Span 1 0 dimensionless C2 Zero 0 0 mV offset C2 Span 1 0 dimensionless When these default values are in effect no software zero or span adjustments are performed When the H2 Zero and H2 Span values are changed the mV signal normally used in the calculation of H20 concentration FCT 31 is transformed according to H20 MV pew H2 Span x mV H2 Zero When the C2 Zero and C2 Span values are changed the mV signal normally used in the calculation of CO con
26. of H O in millibars Saturation Vapor Pressure Table F 1 1000 04 DTE To DCE Cable Connector Descriptions Name Frame ground Received data Transmitted data Request to Send Clear to Send Data Set Ready Signal Ground Carrier Detect Not connected Data Terminal Ready Not connected The 1000 04 cable included is a pin for pin connection between the 25 pin connectors on either end The 1000 04 is terminated with male connectors on both ends a female to female gender changer may be required to connect the LI 6252 to some computers and or printers Connector Descriptions G 1 Sample B Program The following is a sample Borland s C program that could be used to calculate CO and or H20 concentrations The CO calculations use the water correction equations described in Section 3 gascomp c Implements LI COR IRGA equations include lt stdio h gt include lt math h gt static double ppm double mV double Cr double Tirga double vp_r double vp_s double kPa static double cal double mv static double temp_correction double t static double inverse_cal double cppm static double cal_slope double mv static double chi double mfw static double p0_over_p double kPa static double T_cal K_cal A_cal B_cal C_cal D_cal E_cal Water_A static int water_flag static double ppm double mV double Cr double Tirga double vp_r double vp_s double kPa This function implements Equation
27. of Hex 11 resumes transmission System Software 5 17 FCT 18 19 18 Reset Timer Press FCT 18 to reset the Timer function The Timer FCT 45 will begin counting again at zero 19 Full Status Outputs the full status of the analyzer to the RS 232C port in a format that can be read directly back into the analyzer if desired If you are accessing this function remotely you can specify selected information to be sent by entering the optional parameter For example entering 191 would send only the 01 CO3 Cal information and 1913 would send only the 13 RS 232C print list 19 will produce the entire list The entire list will appear something like this 01 3 5970E 01 1 7913E 04 1 4330E 01 9 5609E 06 7 8293E 09 1 1040E 12 7 5366E 17 0 0000E 00 0 02 4 1340E 01 1 5409E 04 6 3281E 03 3 1059E 06 1 1238E 12 0 0000E 00 0 0000E 00 1 0000E 00 05 0 0 0000E 00 0 0000E 00 06 0 0 0000E 00 0 0000E 00 SOK 1 08 1 0 Q0000E 00 1 0000E 00 08 2 0 Q0000E 00 1 0000E 00 09 gt Oyly 13 x150 71 5 9071E 01 72 1 5360E 02 73 43 5 18 System Software FCT 19 74 1 75 0 76 0 77 9 6805E 01 78 1 5000E 00 91 21 31 92 23 29 93 41 42 94 31 32 95 33 39 96 43 44 97 0 0 98 0 0 99 0 0 0000E 00 ij 19 n nis optional parameter for selecting just one output channel A code
28. the 4 to 20mA current loop is selected the output current I milliamps is X Xo XF Xo I 16 To convert the DAC voltage output signal to Umol mol or other units X Wax For the 4 to 20mA channel x AE Xo la x or in terms of a slope and offset xa XE Mo Ko Ke 16 4 6 8 Interfacing Section 6 NOTE The 20 mA signal will not go negative If you wish to use the 20mA option configure the DAC so that the signal will always be positive For example to allow a range of 100 to 100 umol mol set Xo 100 rather than 0 Then 40 umol mol will generate an 8 8 mA signal on DAC 1 20 mA Resolution The DAC s are 12 bit bipolar devices so resolution is given by total range 2 2 The voltage ranges can go positive or negative so resolution is R 2 2 R 2 This corresponds to 2 44 mV on the 5V range and 48 8 uV on the 100 mV range The 4 to 20mA range does not go negative so its resolution is 20 4 2 2 3 91 uA The smallest difference that can be resolved for any variable is AX 2711 Xp Xo 4 88 x 10 4 Xp X voltage and AX 2 12 Xp Xo 2 44 x 10 4 Xp Xo current As an example if Xp 1000 and X 0 the resolution will be about 0 5 umol mol on either voltage channel and 0 25 mol mol on the current channel Timing The DAC outputs change whenever the target channel changes All of the CO values FCTs 22 27 are computed at 5 Hz The H20 values FCTs 32 38 however
29. the analog output channels RS 232C Output Up to 10 different channels can be output in columnar form at a user specified time interval or in response to a command FCT 12 Data are transmitted as ASCII characters that can be captured with a computer or printed on a printer The following communication parameters can be set in the LI 6262 software FCT 17 Baud Rate 300 600 1200 2400 4800 or 9600 Data Bits 7 or 8 Stop Bits 1 or 2 Parity Odd Even or None Check DTR Yes No Check XON XOFF Yes No Analog Output Two linear voltage output channels are provided which have 0 100mV or 0 5V ranges The signals for these channels can be scaled over any concentration range in any units see Section 5 3 FCT 80 The linear channels are available after digital to analog conversions of any channel code 22 27 32 38 or 42 Two analog channels are also available for the raw CO and H20 analyzer outputs Electronic filters provide both 0 1 second and 1 second response times for CO and H20 vapor Units having serial numbers less than IRG3 422 had 1 and 4 second response times unless modified by the 6262 01 or 6262 02 option s Interfacing 6 1 Section 6 6 2 RS 232C Data Transfer Selecting a Cable RS 232C ports on computers and printers often use 25 pin D connectors but this is not always the case The back panel of a typical IBM PC might have 2 such connectors one male and one female The female connector is usu
30. the front panel ON The fan will run and after a few seconds the chopper motor will come up to speed The READY light on the front panel will come on after 1 3 minutes The higher the ambient temperature the longer it takes Any one of the following conditions will prevent the READY light from illuminating Ambient temperature greater than about 55 C Level of CO is too high in the reference cell greater than about 3000 ppm CO or water vapor in the detector caused by the internal soda lime desiccant bottle being exhausted Span potentiometer on the front panel is defective open Setup amp Operation 2 3 Section 2 Low Battery Voltage IMPORTANT The LI 6262 has no built in circuitry for monitoring battery voltage When battery voltage drops below approximately 10 5 volts the analyzer will shut down and data transmission will stop It is therefore suggested that battery voltage be monitored regularly to avoid system shutdown You may wish to monitor battery voltage with an external voltmeter or use a timer with an alarm to alert the user to possible system shutdown If you intend to operate the LI 6262 with battery power for more than 3 hours with the 6000B 6 hours with the 6200B it is recommended that a user supplied battery with a larger storage capacity be connected using the battery leads included with the LI 6262 or that several batteries be used in parallel for longer operation 2 3 Gelman Filt
31. 6200B batteries is built into the LI 6262 and requires only that the AC line cord be connected If you are charging one 6000B battery it will take 1 1 2 2 hours 3 4 hours for the 6200B to recharge the battery to 80 90 of full capacity with the LI 6262 power switch off For best results charge the batteries overnight Batteries may also be charged during operation of the LI 6262 with AC power Charging times will be longer than those given above however At room temperature the 6000B will run the LI 6262 for approximately 3 2 hours and the 6200B will last about 6 4 hours NOTE One set of external leads with a 3 pin plug connection is also included in the spare parts kit for installation with a user supplied battery 10 5 16VDC 1 5 amp maximum Storing The Batteries Store the batteries fully charged and in a cool place if possible For long term storage charge the batteries overnight every month 7 2 Opening The LI 6262 Remove the 4 screws on the bottom of the LI 6262 housing that are closest to the ends of the housing directly opposite the 4 rubber feet There are 2 screws near each end Remove all 8 screws from the top of the housing and slide the cover off Maintenance 7 1 Section 7 7 3 Internal Soda Lime Desiccant NOTE Internal soda lime desiccant must be changed annually CAUTION The instrument should not be turned on for about 24 hours after changing the internal chemicals The time needed w
32. 8 H2 R H20 Reference mmol mol System Software 5 25 FCT 70 71 70 Set Miscellaneous 70 MISC Enters the menu at function 70 T4 The 7x functions include those necessary for using the auxiliary input channel 15 on the back panel terminal strip The input signal is transformed by Y A Bx Cx where x is the signal in mV and the coefficients A B and C are entered in FCTs 71 72 and 75 The value Y can be treated as pressure FCT 43 reference CO FCT 29 or reference H20 FCT 39 according to FCT 73 71 Auxiliary A Offset Auxiliary A Offset value 5 26 System Software FCT 72 73 75 72 Auxiliary B Auxiliary B value ij 72 lt B gt 73 Auxiliary Destination Destination channel of auxiliary Aux Dest 0 input signal NEW __ The auxiliary channel input may be sent to channel codes 29 CO reference 39 H20 reference or 43 pressure Entering any other code at the NEW prompt sets the destination to 0 and deactivates the input channel Setting this destination to 29 39 or 43 causes the values of FCT 59 68 or 77 respectively to be ignored i 73X where x is the destination channel 29 39 43 or lt null gt 75 Auxiliary C Auxiliary C value Aux C 0 0 NEW __ J 75 lt C gt System Software 5 27 FCT 74 74 Average Time Signal averaging time Sets the so
33. I 6262 terminal block Connect the positive input of the data logger to the terminal labeled DAC1 20mA for channel one or DAC2 20mA for channel two Connect the negative input to one of the terminals labeled SIG GND DATA LOGGER a W ee DAC1 5V DAC1 100mv DAC1 20mA SIG GND DAC2 5V DAC2 100mV DAC2 20mA SIG GND CO 0 18 CO 1S H20 0 18 H2O 1S TEMP 5V SIG GND AUX CHASSIS GND Figure 6 2 Connection of data logger for current loop output Interfacing 6 11 Section 6 Measuring Raw Non Linear Analyzer Output To measure the non linearized voltage output of the CO or H20 analyzer 0 1 second response time with a meter or data logger Connect the positive input of the data logger to the terminal labeled CO 0 1S or H20 0 1S see Figure 6 3 Connect the negative input to the terminal labeled SIG GND cable from the data logger is shielded the shield can be connected to the CHASSIS GND terminal To measure analyzer temperature or the voltage output with a different response time connect the appropriately labeled terminal to the positive input of another channel on the data logger The resolution which the data acquisition device should have is dependent upon the noise level of the analyzer 0 2 mol mol C0 typical 0 4 umol mol maximum or 0 05 mmol mol H20 typical 0 2 mmol mol maximum DATA LOGGER 2 oP ON OHA RW ND
34. LI 6262 CO2 H20 Analyzer Operating and Service Manual Publication Number 9003 59 March 1996 Software Version 2 02 LI COR inc P O Box 4425 4421 Superior Street Lincoln Nebraska 68504 Phone 402 467 3576 FAX 402 467 2819 Toll free 1 800 447 3576 U S amp Canada U S and Foreign Patents Pending Federal Communications Commission Radio Frequency Interference Statement This instrument generates and uses radio frequency energy and if not installed and used properly that is in strict accordance with these instructions may cause interference to radio and television reception This equipment is required to comply with the limits for a Class A computing device pursuant to Subpart J of Part 15 of the FCC rules A Class B device is designed to be used in a residential area Class A specifications are designed to provide reasonable protection against such interference in a commercial environment This equipment has been type tested and found to comply with the limits for Class A computing devices and is verified in accordance with FCC Part 15 Subpart J for the Class B limits for a computing device However there is no guarantee that interference will not occur in a particular installation If this equipment does cause interference to radio or television reception that can be determined by turning the instrument off and on the user is encouraged to try to correct the interference by one or more of the follow
35. a single line of data as defined in the Print List FCT 13 to the RS 232C port 13 Set Print List Scrolls through 10 print Print Col 1 0 options NEW __ Data from up to 10 channels may be sent to the RS 232C port at a specified interval see FCT 14 Enter up to 10 channel codes s 21 29 31 39 and 41 47 If all 10 print options are not needed press FCT to exit at any time iil 13x X X X X X X X X X where x is channel code 21 29 31 39 41 E 47 and the last 9 x values are optional 5 14 System Software FCT 14 15 14 Auto Print Time interval between data transmissions through the RS 232C port Enter specified interval in seconds 0 2 0 5 or 1 3600 at which to transmit data defined at FCT 13 to the RS 232C port The interval can be 0 2 0 5 or any value from 1 to 3600 14x where x is any number 0 2 0 5 or 1 to 3600 15 Auto Header Number of data lines between Auto Header 0 headers 1 999 NEW __ The column header interval is the number of data lines which will be printed between column headers For example entering 5 will cause a column header to be printed after every 5 lines of data E 15x where x is any number from 1 to 999 System Software 5 15 FCT 16 16 Print Calibration Data Press FCT 16 to send the current calibration stack for H20 CO7 and Miscellaneous channel codes to th
36. ad for selecting software functions and entering numbers Hose Connections Rapid connect hose fittings for 4 mm ID x 6 mm OD plastic tubing Temperature Range 0 50 C ambient 0 50 C optical bench temperature Power Requirements 100 130 VAC or 200 260 VAC 47 65 hertz or 10 5 16 VDC 1 5 amp maximum Power Consumption 8 12 Watts DC dependent on temperature Size 33 5 L x 13 W x 24cm D 13 x 5 x 9 5 Weight 3 5 kg 7 7 Ib H O Analyzer Specifications Range 0 to 7 5 kPa or 40 C dewpoint Optical bench and interconnecting hoses must be maintained above the dewpoint temperature by the user Accuracy 1 of reading at lower vapor pressures lt 1 of reading Zero Drift lt 0 5 mB in 24 hours from 10 40 C Span Drift lt 1 in 24 hours from 10 40 C neglecting density changes Noise Level kPa peak to peak Typical 0 002 kPa at 2 kPa with 1 second response time 0 006 kPa at 2 kPa with 0 1 second response time Noise Level dewpoint peak to peak Typical 0 02 C at 2 kPa with 1 second response time 0 06 C at 2 kPa with 0 1 second response time CO Analyzer Specifications Range 0 3000 ppm Accuracy ppm at 350 ppm lt 3 ppm maximum 2 ppm at 1000 ppm lt 6 ppm maximum Zero Drift over time First Hour lt 5 ppm at 25 C After first hour lt 1 ppm per hour at 25 C Zero Drift with temperature 0 12 ppm C typical 0 45 ppm C maximum Span Drift Typically lt 1 ppm in 24
37. ade function so the display will show 00 SETUP 7 Press FUNCTION to exit the menu 8 Press FCT 91 This will directly execute the function described in step 3 above which prompts for a new channel code for the top line of display 1 9 Press ENTER to retain the displayed value of this constant or press FUNCTION to cancel the operation 5 2 System Software FCT 00 Remote Commands Certain function codes can be sent to the LI 6262 from a computer or terminal as shown on the console command card a computer and LI 6262 for data transfer and for sending remote L commands Look for the icon at left in the following section for examples of how to format entries to be sent to the LI 6262 iy Section 6 2 gives a complete explanation of how to connect your 5 3 Console Commands This section discusses each function in detail It may be helpful to reference the console command summary card while reading through the definitions of the following functions 00 Setup Scroll T UP J4 DOWN or ENTER 00 lt SHLUPRA AA hee ees System Software 5 3 FCT 01 01 CO Calibration Function 01 is actually a group of functions executing FCT 01 performs functions 51 59 and 76 The LI 6262 is calibrated using a 5th order calibration polynomial of the form mol mol A mV B mV 2 C mV D mV 4 E mV The calibration coefficients T K A B C D E are entered into the LI 6262
38. ak te Ae Figure 5 2 Accumulating total area A and non peak area Channel 47 displays the peak value of the target channel during integration ij x09x start start value stop stop value x is channel Code 22 29 or 32 39 to be integrated and denotes optional start and 4 stop values The start value is required only if start 2 and the stop value is required only if stop 2 or 3 Start Description Stop Description 1 On Exit 1 Manual 2 Threshold 2 Threshold 3 Elapsed Time 5 12 System Software FCT 09 Examples 409227 2 7 2072 Integrate channel 22 CO umol mol absolute starting when it goes above 0 5 umol mol and ending when it falls below 0 5 mol mol 0932 1 1 Integrate channel 32 H20 mmol mol absolute starting immediately and ending when the next is received 0922 2 100 3 30 Integrate channel 22 CO umol mol absolute starting when it goes above 100 mol mol and ending 30 seconds later 10 Print Commands 10 PRINT Enters menu at command 10 Tal System Software 5 13 FCT 11 13 11 Print Header Press FCT 11 to send a column header to the RS 232C port The headers that are printed correspond to the channels specified by the Print List FCT 13 Appendix D lists the labels for each channel code Function 11 may be used at any time to output a single row of column headers 12 Print Data Press FCT 12 to send
39. allows for automatic pressure corrections to be performed During installation an adapter board is connected to the analyzer s digital board The adapter board sends the transducer mV output to the Auxiliary terminal 15 on the terminal strip Figure 6 6 Because the mV output of the transducer is connected to the Auxiliary terminal on the terminal strip the signal can be measured by connecting a voltmeter or datalogger to the Aux and Sig Gnd terminals Pressure can then be calculated externally if desired Internal computations are performed provided FCTs 71 72 73 and 75 are set correctly see Software Considerations below Digital Board Adapter Board Power Pressure Supply Transducer K amp Terminal Strip alsataalolalalalaletelalalate 123 4 5 6 7 8 9 10 11 12 13 14 15 16 AUX INPUT terminal 15 Pressure transducer mV output Figure 6 6 Block diagram of electrical connections Software Considerations The pressure value kPa used in the calculation of CO is stored at channel code 43 Pressure can be entered as a constant at FCT 77 or it can be calculated from the 6262 03 mV signal provided to the Aux Input If you are using the 6262 03 the Auxiliary Destination FCT 73 must be specified Interfacing 6 15 Section 6 as channel 43 Pressure Specifying the Auxiliary Destination as channel 43 causes any constant pressure entered in FCT 77 to be ignored
40. ally the parallel interface and the male connector is usually the RS 232C port However an RS 232C port might use male or female connectors so verify what is present before connecting anything to it Jt is possible to damage a serial interface by connecting it to another type of interface The RS 232C port on the LI 6262 is the female 25 pin D connector on the back panel labeled RS 232C DCE The LI 6262 is configured as Data Communications Equipment DCE which means that it can communicate directly with computers RS 232C printers and other devices configured as Data Terminal Equipment DTE using only a cable that has pin for pin connections between the connectors on each end The LI COR 1000 04 RS 232C cable will work with most computers and printers with a 25 pin connector and the 1800 04 RS 232C cable will work with most computers that have a 9 pin AT style RS 232C port Most other cables that are manufactured for DCE to DTE RS 232C data communications will also work If your computer is configured as DCE not normally the case use the 1000 03 RS 232C cable or any other cable that can act as a null modem DCE to DCE in this case 6 2 Interfacing Section 6 Software Configuration Functions 11 17 are used to set up RS 232C data transfer They are accessed directly or via the PRINT stack FCT 10 The following example illustrates how to configure the LI 6262 to transmit differential CO channel code 23 absolute HO channe
41. at the factory and are shown on the calibration sheet CO reference mole fraction umol mol and the choice of water correction depend upon your system setup See functions 59 and 76 for complete descriptions Check the calibration sheet to verify that the correct values are entered Prompt Description Related Function C2 T Calibration Temperature 51 C2 K Calibration Constant K 52 C2 A Calibration Coefficient A 53 C2 B Calibration Coefficient B 54 C2 C Calibration Coefficient C 55 C2 D Calibration Coefficient D 56 C2 E Calibration Coefficient E 57 C2 R CO Reference umol mol 59 BandBrd Dil REF Water correction selection 76 01T K A B C D E REF VAPOR FLAG 5 4 System Software 02 H O Calibration Function 02 performs functions 61 65 and 68 FCT 02 03 H 0 calibration coefficients T K A B C are factory entered and are on the calibration sheet H20 reference mole fraction is in units of millimoles mole of water vapor in the reference cell Verify these values with the H20 calibration sheet and change if needed Prompt Description H2 T Calibration Temperature H2 K Calibration Constant K H2 A Calibration Coefficient A H2 B Calibration Coefficient B H2 C Calibration Coefficient C H2 R H20 Reference mmol mol W 02T K A B C REF 03 Set Miscellaneous Function 03 performs functions 71 75 and 77 Prompt Description P kPa Barometric Pressure Avg s Sig
42. centration FCT 21 is transformed according to CO 7 MVnew C2 Span x mV C2 Zero The values of CO2 MVypew and H20 mVypey are used by the calibration polynomials to compute concentration but do not change the raw CO mV signal displayed at channel 21 or the raw H20 mV signal displayed at channel 31 or the output RS 232C values of either The values of H2 Zero and H2 Span and C2 Zero and C2 Span can be entered via the keypad at FCT 08 or by sending a remote command sequence When sending a remote command you have the option of entering the Zero and Span values or allowing the analyzer software to calculate the values for you The following examples demonstrate how you can calibrate your LI 6262 in software for both absolute and differential measurements Remote Commands The remote command sequence for the CO software zero and span is 4 10 Calibration Section 4 081 C2 Zero C2 Span CO2 concentration mol mol The remote command sequence for the H20 software zero and span is 082 H2 Zero H2 Span H20 concentration mmol mol The last parameter CO or HO concentration is optional and is used only when you want the software to compute the zero or span value If the concentration is set to zero the software computes the zero offset and stores it as C2 Zero or H2 Zero When zero is entered you must have the same gas concentration flowing to both the sample and reference cells of the analyzer If any value other than z
43. chines Corp PC TALK is a trademark of Freeware ProComm is a trademark of Data Storm Technologies Printing History New editions of this manual will incorporate all material since the previous editions Update packages may be used between editions which contain replacement and additional pages to be merged into the manual by the user The manual printing date indicates its current edition The printing date changes when a new edition is printed Minor corrections and updates which are incorporated at reprint do not cause the date to change 1st Printing April 1990 2nd Printing October 1991 3rd Printing March 1996 iii Table of Contents Section I Unpacking and Inspection 1 1 What s What cernas eisers Keini eii eese A Ge oa ae 1 1 1 2 Checking the Batterites 2 escssccseshaves tatsonsscetsesseatsedssstsscesativeasseonsens 1 3 Section Il Setup and Operation 2 1 Setup and Operation oo cece ceeesecseeeceeceseceeceseeseeeseseeseseeeaeeaes 2 1 D2 Power OMe a a ai E EEE AE EEA EEE 2 3 2 3 Gelman Filter Installation eee cseeseceeceseceeceseeeeeeseeeeeneeees 2 4 2 4 Absolute vs Differential Mode Operation 0 eee eee eeeeeeeeeee 2 5 Section Ill Theory Of Operation 3 1 General Description as ssis cesses sste e N E RE 3 1 3 2 Calculating Gas Concentration General eee eeeseeecseeeseeeee 3 2 3 3 Calculating CO Concentration eee eee eeeeseeeseeseecaecssecneesaeeaees 3 6 3 4 Calculat
44. come at an irregular interval they change at 5 Hz but 2 of the 5 measurements each second are missed while the temperature and auxiliary input channel are measured so actually only 3 changes occur in 1 second This irregularity makes outputting H2O signals on the DAC inappropriate for high speed regular sampling applications such as eddy correlation Users needing high speed regular sampling should use the non linear outputs for H20 and possibly CO7 if gt 5 Hz is required Interfacing 6 9 Section 6 Terminal Connections Voltage Figure 6 1 shows an example connection of a data acquisition device to the LI 6262 to measure the linear output of channel 1 Connect the positive input of the data logger to the terminal labeled DAC1 5V or DAC1 100mV The negative input should be connected to the terminal labeled SIG GND Connect another input from the data logger to the terminal labeled DAC2 5V or DAC2 100mV to measure the linear output of channel 2 1 act 5v 2 DAC1 100mV 3 DAC1 20mA 4 SIG GND 5 DAC2 5V 6 HB DAC2 100mv 7 HB DAc2 20ma DATA LOGGER o MB sic ano 9 co 0 1s 10 CO 1S H 12 C W ois 13 W Temp 5v 14 gt siaanpb 15 I aux 16 CHassis GND Figure 6 1 Connection of data logger for linear output 6 10 Interfacing Terminal Connections Current Section 6 Figure 6 2 shows the proper connection of a data acquisition device to the L
45. correctly when pressed The D A Digital to Analog Test is used to test the digital to analog conversion capabilities of the LI 6262 Enter a value in volts to be output to channel 1 or 2 which can be measured with a metering device Prompt for digital to analog DA1 0 0 conversion value in volts NEW __ 5 8 System Software FCT 08 The A D Analog to Digital Zero Test displays the analog count of output channels and 2 If the A D converter is functioning properly these values should be nearly identical approximately 32 700 The A D Analog to Digital Span Test displays the analog count of output channels 1 and 2 as well as the analog count and actual mV output of the CO Temperature and Auxiliary output channels The RAM Random Access Memory Test shows the amount of available system RAM The LI 6252 has approximately 8K bytes of RAM The EEPROM Electrically Erasable Programmable Read Only Memory Test shows the amount of available ROM memory The system parameters entered by the user are stored in EEPROM The LI 6262 has approximately 32K bytes of ROM program memory Geopotential Displays the geopotential height in feet or meters based on the current value of pressure at channel 43 This value can be provided by a sensor FCT 73 or as a keyboard entered constant FCT 77 Press the up or down arrow keys to toggle between units of feet and meters Geopotential height is height above sea level i
46. e Software Revision I D CO2 CALIBRATION CO Calibration T CO Calibration K CO Calibration A CO Calibration B CO Calibration C CO Calibration D CO Calibration E CO Reference umol mol H20 CALIBRATION H20 Calibration T H20 Calibration K H20 Calibration A H 0 Calibration B H20 Calibration C H20 Reference mmol mol Page 5 21 5 21 5 21 5 21 5 21 5 21 5 21 5 21 5 21 5 21 5 22 5 22 5 22 5 22 5 22 5 22 5 23 5 23 5 23 5 24 5 24 5 24 5 24 5 24 5 24 5 24 5 24 5 24 5 25 5 25 5 25 5 25 5 25 5 25 5 25 Function Code Description MISCELLANEOUS Auxiliary A Offset Auxiliary B Auxiliary Destination Average Time Auxiliary C Vapor Flag Pressure Vapor Correction a D A Conversion Code 1 D A Conversion Code 1 Min D A Conversion Code 1 Max D A Conversion Code 2 D A Conversion Code 2 Min D A Conversion Code 2 Max DISPLAYS Displays 1 9 Software Commands Page 5 26 5 27 5 27 C 3 B Channel Code Headers The following table shows the way in which channel code headers will appear when sent from the LI 6262 to a terminal or printer through the RS 232C port Header C2 mV C2 um m AC2um m C2 Pa AC2 Pa C2 ug g AC2ug g REFum m H2 mV H2 mm m AH2mm m H2 kPa AH2 kPa H2 mg g AH2 mg g DewPt C REFmm m Temp mV Temp C P kPa Aux mV Timer Description CO raw mV CO umol mol absolute CO mol mol diff
47. e Pump must be turned off independently it will not shut off when the LI 6262 is powered off Turn on the pump Calibration 4 7 Section 4 P SAN Figure 4 3 6262 04 Reference Pump installed on LI 6262 back panel 4 8 Calibration Section 4 4 5 Pressure Corrections NOTE This section may be disregarded if the 6262 03 Pressure Transducer is installed The LI 6262 is sensitive to pressure differences between the sample and reference cells The span of the analyzer should be set with a span gas flow rate equal to the flow rate at which it will be used With the flow of the analyzer vented to the atmosphere the effect is minimal but if the flow from the analyzer must pass through tubing fittings etc the pressure increase must be taken into account If it is not convenient or possible to have the span gas flow rate equal to the flow rate used during measurement the pressure effect can be characterized and the span set at zero flow after complete purging of the sample cell The procedure for this is as follows 1 Connect a stable source of air to the input of the analyzer and adjust the flow rate to be equal to the flow rate at which measurements will be taken 2 Monitor CO or H20 on the display and record the concentration after the reading has stabilized 3 Shut the flow off leaving this same concentration in the sample cell 4 Record the concentration from the display Correction factor Conc with
48. e RS 232C port The output includes the calibration constants auxiliary channel equations and zero and span parameters for H2O and CO2 The output should look similar to this C02 T 3 5970E 01 K 1 7913E 04 A 1 4330E 01 B 9 5609E 06 Ci 7 8293E 09 D 1 1040E 12 E 7 5366E 17 Ref 0 0000E 00 Zero 0 0000E 00 Span 1 0000E 00 VC Corrections Off H20 4 1340E 01 1 5409E 04 6 3281E 03 3 1059E 06 1 1238E 12 Ref 0 0000E 00 Zero 0 0000E 00 Span 1 0000E 00 QwWwPrPAH MISC AUX DEST 43 AUX A 5 9071E 01 AUX B 1 5360E 02 AUX C 0 0000E 00 AVG TIME 1 PRESSURE 9 6805E 01 VP CORR A 1 5000E 00 5 16 System Software FCT 17 17 Set RS 232C Port Baud 300 Sets parameters for data output Ta Scroll the options in the each parameter using the up and down arrow keys and press Enter to select the value The parameters for data output through the RS 232C port are as follows See Section 6 for further details on data communications Baud rate 300 600 1200 2400 4800 or 9600 Data bits 7 or 8 Stop bits 1 or 2 Parity None Even or Odd Check DTR Data Terminal Ready Yes or No This is a hardware handshaking line The LI 6262 looks for DTR on pin 20 Check XON OFF Software Handshaking Yes or No Controls the flow of data between transmitting and receiving devices Receipt of Hex 13 halts transmission receipt
49. e a soda lime desiccant tube as described in Section 7 4 and attach to the SCRUBBER holder on the back panel Differential Mode Operation Orient the scrubber tube so that the soda lime is on the bottom and the magnesium perchlorate is on top Attach the bottom hose nearest the soda lime to the FROM CHOPPER fitting Attach the top hose nearest the perchlorate to the TO CHOPPER fitting Figure 2 1 Figure 2 1 Hose connections for operation in differential mode IMPORTANT Attach the hoses as shown in Figure 2 2 The hose nearest the soda lime is attached to the FROM CHOPPER fitting and the hose near the magnesium perchlorate is attached to the TO CHOPPER fitting This ensures that CO is purged first and then water vapor If this sequence is reversed the air will pick up water vapor from the soda lime before being returned to the chopper housing 2 6 Setup amp Operation Section 2 To chopper lt Magnesium Perchlorate Fiberglass Wool Soda Lime From chopper gt Figure 2 2 Hose attachments to external soda lime desiccant tube assembly Absolute Mode Operation IMPORTANT Air flow created by movement of the chopping shutter disc is sufficient to purge the reference cell of CO7 but is not sufficient to remove all of the water vapor in the reference cell For this reason an auxiliary pump such as the 6262 04 must be used when operating in absolute mode See Section 4 4 for more information
50. e i yee A hon aanranursee AN Oak wD Figure 6 4 Connection of an external sensor for analog signal input Interfacing 6 13 Section 6 The calibration equation is of the form Y A BX CX2 where A B and C are FCTs 71 72 and 75 and X is the actual mV output of the sensor See Section 5 3 FCT 70 6 5 Temperature Output The analyzer temperature can be recorded by connecting a logging device to the terminal strip on the analyzer back panel Connect the positive lead from the data logger to the terminal labeled TEMP 5V and the negative lead to the terminal labeled SIG GND Fig 6 5 Temperature output is linear and can be computed according to T C eo 4096 mV where V the analyzer output in millivolts and OV 0 C 1 JB pact sv 2 _ DACc1 100mv 3 MM Daci 20ma 4 SIG GND 5 DAC2 5V 6 HB DAC2 100mv 7 HB DAc2 20ma DATA LOGGER o sic cno 9 W co 01s 10 W cois 11 W oos 12 gt W ois 134 W Tempe 5v 144 sia Gnp 15 aux 16 CHASSIS GND Figure 6 5 Connection of data logger for analyzer temperature output 6 14 Interfacing Section 6 6 6 Using the 6262 03 Pressure Transducer The 6262 03 is located inside the LI 6262 case and senses pressure from a manifold on the optical cell Because the calibration function used in LI COR gas analyzers will correct for pressure changes if the pressure in the optical cell is known the 6262 03
51. e power transformer core 7 6 Maintenance Trouble shooting This section summarizes some things that might go wrong and suggests what to do about these problems should they happen Power ON Problems e Nothing happens Try another battery or if using AC power check the AC voltage switch on the back panel to make sure that it is set properly Check the fuses to see if one has blown e Display flickers then goes out The analyzer is probably shutting down because the battery voltage is too low lt 10 5 V Try another battery Ready Light Won t Illuminate The ready light may fail to illuminate for a number of reasons some of these problems you can fix yourself e Ambient temperature is greater than about 55 C e CO level in the reference cell is greater than about 3000 ppm e CO or water vapor in the detector caused by internal soda lime desiccant bottle leaking or if the internal soda lime desiccant has been exhausted e Span potentiometer has an open circuit Troubleshooting 8 1 Section 8 Zero and or Span Adjustments Difficult to Set If the zero and or span adjustments are difficult to set check to see that the analyzer is configured correctly jumper tubes soda lime desiccant etc Also check to make sure that the flow through the analyzer is first entering the portion of the scrubber tube assembly containing the soda lime not the magnesium perchlorate Make sure external soda l
52. ear quantum counter that is over much of its range the detector signal output v is proportional to the number of photons reaching the detector The output voltage V that is used to compute CO2 mole fraction is proportional to the difference between the signals generated by the detector when it sees the sample cell v and when it sees the reference cell v 3 2 Theory of Operation Section 3 V k V Vs 3 1 The analyzer operates in such a way as to keep v constant so we can factor v out of the quantity in parentheses define K kv and obtain v x 2 3 2a Vy In absolute mode the instrument is operated with no CO3 in the reference cell so v is proportional to maximum photon throughput The sample cell normally contains CO which reduces the photon flux reaching the detector through the sample cell and reduces v Therefore the ratio V v gives the ratio of photon flux in the presence of CO and in its absence which is just the transmittance T Since absorptance A equals 1 t we can also write equation 3 2 as V K 1 7 3 2b and V KA 3 2 c The constant K is given on the calibration sheet Equation 3 2c indicates that the analyzer output voltage is proportional to absorptance however absorptance is a non linear function of CO mole fraction Absorptance and analyzer output voltage both increase with increasing CO mole fraction in the sample cell Figure 3 1 illustrates a typical relationship between gas concentrat
53. el to output through analog output channel 1 82 D A Conversion 1 Minimum Digital channel value which corresponds to OV or 4mA on DAC 1 83 D A Conversion 1 Maximum Digital channel value which corresponds to full scale 5V 100mV or 20mA on DAC 1 System Software 5 33 FCT 84 86 84 D A Conversion Code 2 DAC 2 Code e Conversion 2 same as NEW __ 85 D A Conversion 2 Minimum Digital channel value which P ON corresponds to OV or 4mA on ake DAC 2 86 D A Conversion 2 Maximum 2 5y Digital channel value which eS corresponds to full scale 5V NEWS a 100mV or 20mA on DAC 2 5 34 System Software FCT 90 99 90 99 Displays 90 DISP Enters menu at function 90 T4 Nine two line displays can be defined with functions 91 99 Function 91 defines display 1 accessed by pressing the 1 key 92 defines display 2 etc Displayable quantities are 21 29 31 39 or 41 45 All displays can be defined in one operation at FCT 04 or they can be defined individually using FCT 91 99 as shown below Channel code for top of display 1 Channel code for bottom of 1 Bottom display 1 NEW __ 91x x 92x x 93x x etc where x is any channel code 21 27 29 31 39 and 41 47 System Software 5 35 O Interfacing 6 1 General Information Data can be obtained from the LI 6262 in three ways 1 from the display 2 from the RS 232C port or 3 from one of
54. er Installation IMPORTANT Always install the external air filters before operating the LI 6262 Insert filters into both the SAMPLE and REFERENCE airstreams before they enter the LI 6262 Failure to do this will lead to contamination of the sample and reference optical paths which can cause large zero offsets that may require expensive repairs The Gelman polypropylene filters included use PTFE filter elements with a 1 um pore size They have excellent particle retention very low water sorption little flow restriction and small internal volumes These filters will not fit inside the LI 6262 case and must be used externally In absolute mode insert a filter between the scrubber tube outlet top and the REFERENCE IN port Figure 2 3 Use a jumper tube to connect the REFERENCE OUT port to the TO CHOPPER port The scrubber tube inlet bottom is connected to the FROM CHOPPER port Air supplied to the sample cell must also pass through a filter before it enters the LI 6262 In differential mode place a filter in the sample airstream before it enters the SAMPLE IN port on the LI 6262 Place a second filter in the reference airstream before it enters the REFERENCE IN port 2 4 Setup amp Operation Section 2 Replace the filters when flow rates drop due to particle retention or when the apparent LI 6262 response to changes in humidity becomes slow due to filter retention of hygroscopic material When using the LI 6262 in high fl
55. er disc is sufficient to purge the reference cell of CO2 but it is not sufficient to remove all the water vapor in the reference cell For this reason an auxiliary pump such as the 6262 04 or the LI 670 Flow Control Unit must be used when operating in absolute mode 6000B Rechargeable Battery provides 3 2 hours of battery life 6200B Rechargeable Battery provides 6 4 hours of battery life LI 6020 Battery Charger 92 138 184 276 VAC 47 to 63 Hz 1800 04 RS 232C Cable Used to connect the LI 6262 DCE to a standard IBM AT type 9 pin RS 232C communications port In addition LI COR manufactures a portable dew point generator LI 610 and a flow control unit LI 670 which are valuable accessories for calibrating and operating the LI 6262 LI 610 Portable Dew Point Generator The LI 610 is an ideal field portable system for calibrating the LI 6262 and can also be used to provide a known water vapor source for use in environ mentally controlled measurement chambers The LI 610 is a precision instrument that provides a controlled water vapor source of known dew point The LI 610 has the ability to generate stable dew points from 0 to 50 C with high accuracy 0 2 C The water vapor source can be derived from any input air stream including ambient air eliminating the need for external tanks or mixing of gases The dew point temperature of the air stream can be viewed on the LI 610 s 4 1 2 digit LCD display or output to the
56. erence cell Set the CO reference FCT 59 to the span gas mole fraction umol mol Display differential CO FCT 23 4 2 Calibration Section 4 7 There will likely be a small zero offset Adjust the zero potentiometer to read zero 8 To check the span flow a different gas through the sample cell FCT 22 should show that value If you don t have a second gas you could scrub the sample cell and see if FCT 22 reads zero Adjust the span as needed 9 Lock the potentiometers H O Zero and Span Calibration It is likely that zero and reference gases containing known amounts of water vapor will be produced by a dewpoint generator such as the LI 610 or measured with a dewpoint hygrometer However the LI 6262 requires that the reference cell water vapor mole fraction be entered as a parameter before differential measurements can be performed Therefore it will often be necessary to convert a dewpoint temperature into a vapor pressure and then into mole fraction Vapor pressure can be obtained from dewpoint temperature by making reference to Appendix F or by calculation Note that Appendix F gives vapor pressure in millibars these values must be divided by 10 to convert to kilopascals Vapor pressure e kPa can be calculated as 7 6448T e 0 61083 x10 77 2T where Tg is the dewpoint temperature The reference water vapor mole fraction mmol mol is Wref 1000 p where P is the local barometric pressure in k
57. erential CO Pa absolute CO Pa differential CO ug g absolute CO gt ug g differential CO reference mol mol H20 raw mV H20 mmol mol absolute H20 mmol mol differential H20 kPa absolute H20 kPa differential H20 mg g absolute H20 mg g differential H20 Dewpoint C H270 reference mmol mol Temperature mV Temperature C Pressure kPa Auxiliary mV Timer s Channel Code 21 22 23 24 25 26 27 29 31 32 33 34 35 36 37 38 39 41 42 43 44 45 Channel Code Headers D 1 COs H 0 ANALYZER ia L1 6262 LL Console Commands Setup Commands 10 PRINT 11 Print Header 12 Print Data 13 Set Print List 14 Auto Print 15 Auto Header 16 Print Calibration Data 17 Set RS 232C Port 18 Reset Timer 19 Full Status 00 SETUP 01 Set CO Calibration 02 Set HO Calibration 03 Set Miscellaneous 04 Set Displays 05 Set D A Conversion 1 06 Set D A Conversion 2 07 Backlight ON OFF 08 Test Menu 09 Integrate Channel Codes 20 CO2 21 CO raw mV 22 CO mol mol abs 23 CO mol mol diff 24 CO Pa abs 25 CO Pa diff 26 CO ug g abs 27 CO ug g diff 29 CO mol mol ref 30 H20 31 H20 raw mV 32 H20 mmol mol abs 33 H2O mmol mol diff 34 H O kPa abs 35 H20 kPa diff 36 H20 mg g abs 37 H2O mg g diff 38 H20 Dewpoint 39 H O mmol mol ref 40 MISC 41 Temperature mV 42 Temperature C 43 Pressure kPa 44 Auxiliary mV 45 Timer 46
58. ero is entered the software computes the dimensionless span value for that concentration as Span Veale Vmeas Fl Span To T V meas NOTE The LI 6262 will not accept remote commands while the Test Menu is active Exit the Test Menu and enter display mode the remote command will then be executed Absolute Mode Calibration 1 Set the CO zero Flow CO gt free air through the chopper housing reference and sample sides of the analyzer Send remote command 081 0 1 0 to set the zero 2 Set the CO span Let s assume that we are using a 500 ppm span gas Flow CO gt free air through the chopper housing and reference side of the analyzer Flow 500 ppm span gas through the sample side of the analyzer Send remote command 081 0 1 500 to set the span Differential Mode Calibration Assume for this example that we are using precision span tanks of 300 and 500 ppm CO gt 1 Set the CO3 zero Flow CO gt free air through the chopper housing and the 300 ppm gas through the reference and sample sides of the analyzer Send remote command 081 0 1 0 to set the zero Calibration 4 11 Section 4 Set FCT 59 CO reference to 300 2 Set the CO span Flow CO gt free air through the chopper housing Flow 300 ppm span gas through the reference side of the analyzer Flow 500 ppm span gas through the sample side of the analyzer Send remote command 081 0 1 500 to set the span The procedure for setting
59. f infrared radiation is due to energy induced changes in vibrational and rotational energy states Such energy states are altered by intermolecular collisions which increase in number as pressure increases The kinetic theory of gases and quantum mechanics predicts that absorption band widths increase with pressure and it is observed that broad band infrared absorption increases as pressure increases at constant absorber concentration Not all gases are equally effective in causing pressure induced line broadening Gases that are similar are more effective than dissimilar gases This effect is embodied in the concept of equivalent pressure or effective pressure P Total pressure P is equal to the sum of partial pressures of component gases while equivalent pressure is defined as Pe ajpy aopot where a are weighting factors representing the pressure broadening effectiveness of each gas species relative to nitrogen ay 1 For CO3 in nitrogen Pe py 1 3 pco 2 Consider a simple atmosphere made up of H20 vapor with pressure e plus dry gases with pressure Pg so that P Pq e or in mole fraction units 1 Xqg Xw 3 18 where Xq is the mole fraction of all dry gases and Xw is the water vapor mole fraction e P The equivalent pressure will be P Xap aye In principle Pe will vary with CO partial pressure but the CO partial pressure is so small that it can 3 8 Theory of Operation Section 3 be neglected
60. ftware signal averaging time from 0 to 30 seconds Increasing the average time decreases the noise level in any displayed channel The digital signal displayed is averaged over the entire time span set after conversion from the analog signal This results in a significant decrease in the apparent noise level but slows the response time as well This average time affects all computed values of CO2 FCTs 22 to 27 and H20 FCTs 32 38 whether displayed or output to a DAC channel or output by RS 232C It does not affect the raw mV signals on the back terminal strip Setting Average Time to zero will turn off all digital averaging and the displayed or output values of CO2 and H20 will reflect the hardware response time i 74X where x is any value from 0 30 seconds 5 28 System Software FCT 76 76 Vapor Flag Water corrections may be selected in the LI 6262 using FCT 76 The Vapor Flag default setting is for both pressure broadening and dilution corrections to be applied if a System Reset FCT 08 is performed See Sections 3 4 and 3 5 for complete explanations of the vapor corrections No vapor corrections performed Corrections Off State 0 Talia Band Broadening aa ot pano pegacening Teal Band broadening amp dilution corrections applied State 2 BandBrd Dil REF T4 76X where x is 0 1 or 2 for no correction correct for band broadening or correct for band b
61. hat is driving it Xp X X Ae Moly X R where R full scale voltage range 5V or 100mV Xp the value of X corresponding to full scale voltage set in FCT 83 or 86 and X the value of X corresponding to zero volts set in FCT 82 or 85 For current I x Seo 5Xo XF 16 4 where Xp is the value of X corresponding to 20mA and X is the value of X corresponding to 4mA the minimum X value expected because unlike the voltage outputs the current output cannot go negative System Software 5 31 FCT 80 The output resolution of X will be AX 4 88 x 104 Xp Xo voltage and AX 2 44 x 104 Xp Xo current If voltage is measured the 0 5V range should be used whenever possible The 0 100 mV range is provided for measuring or logging devices with a more limited voltage range some resolution may be lost due to signal noise considerations when using the smaller output range The output impedance of the 0 100 mV range is 50 100Q so a measuring or logging device with a high input impedance should be used Note that resolution is maximized by minimizing the range to be covered For example if you are making CO 2 measurements that are always less than 400 ppm set the DAC to cover only that range rather than 0 to 1000 or 0 to 3000 5 32 System Software FCT 81 83 81 D A Conversion Code 1 Channel code for digital to eae Code analog conversion 1 Enter channel code 22 27 32 38 or 42 as the chann
62. hours at 25 C and 350 ppm absolute mode Short Term Repeatability 0 2 ppm at 350 ppm Water Sensitivity lt 2 ppm from 0 4 0 kPa at 350 ppm Software algorithm corrects for both band broadening and dilution effects Calibration Factory linearization over 0 3000 ppm range using NIST traceable standard gases Noise Level ppm peak to peak Typical 0 2 ppm Maximum 0 4 ppm at 350 ppm with 1 second response time 0 6 ppm typical 1 ppm maximum at 350 ppm with 0 1 second response time A 2 Specifications 6262 03 Pressure Transducer Specifications Pressure Range 0 to 115 kPa absolute Accuracy with software correction 0 1 full scale Resolution 0 002 kPa Signal noise peak to peak 0 002 kPa typical Power consumption 50 mA steady state Weight 0 88 oz 25 g Specifications A 3 w Suppliers z The company names addresses and phone numbers are the most current we have at the time of this printing In some cases the information may change without notice Soda Lime 6 12 mesh and Magnesium Perchlorate Anhydrous Mg Cl04 2 GFS Chemicals P O Box 245 Powell OH 43065 Phone 614 881 5501 FAX 614 881 5989 Toll free 800 858 9682 Fisher Scientific 711 Forbes Avenue Pittsburgh PA 15219 4785 Phone 201 467 6400 FAX 201 379 7415 Toll free 800 776 7000 Toll free FAX 800 926 1166 Thomas Scientific P O Box 99 Swedesboro NJ 08085 6099 Phone 609 467 2000 FAX 609 467 3087
63. ill depend of course on how much CO and or water vapor gets into the detector housing during the exchange of bottles Leaving the instrument off is done so that water vapor which may have entered the system during the time the chemicals were exchanged will not condense in the optical path when the Peltier coolers controlling the detector temperature are powered up There is a small plastic bottle inside the LI 6262 that contains a mixture of soda lime and anhydrous Mg C104 magnesium perchlorate This bottle is attached to the CO H O analyzers detector housing Its purpose is to keep the detectors free of CO and water vapor and their dewpoints below 5 C If the CO H O concentration in the detectors rises the analyzer response curves will change and the calibration polynomials will no longer match the response curves and the factory supplied calibration functions will be invalid If the dewpoint in the detectors rises above 5 C condensation may form resulting in a large shift in the zero and or span The READY light may also fail to light For these reasons the internal soda lime desiccant must be changed annually The plastic bottle of soda lime desiccant is located inside the nickel plated desiccant bottle cover which is connected perpendicularly to the detector housing Figure 7 1 The bottle cover is attached with 2 Allen head screws which may be removed with the hex key included in the LI 6262 spare parts kit Be carefu
64. ilopascals See Section 3 4 for further information Calibration 4 3 Section 4 The H O zero and span calibration is identical to that for CO2 however allow adequate time for equilibration several minutes after changing the humidity 1 4 4 Set the H2O reference to zero FCT 68 If you are not using the 6262 03 Pressure Transducer enter the barometric pressure in FCT 77 Display absolute H20 FCT 32 34 or 36 Flow a dry gas through both sides of the analyzer Unlock the H20 zero potentiometer and adjust until the absolute H2O concentration on the display reads zero With a dry gas on the reference side flow a span gas through the sample cell Set the span potentiometer to read the value of the span gas in the appropriate units Flow the span gas through both cells of the analyzer at the same flow rate Set the H20 reference FCT 68 to the value of the span gas in the appropriate units Display differential H2O FCT 33 35 or 37 There will likely be a small zero offset Adjust the zero potentiometer to read zero To check the span flow a different humidity through the sample cell FCT 32 or 34 or 36 should show that value Adjust the span as needed Lock the potentiometers Calibration Section 4 4 3 Absolute Mode Calibration The procedure for setting the zero and span potentiometers in absolute mode is described in Steps thru 5 above for differential mode calibration 4 4 H O Absolute Mode Cau
65. ime desiccant is fresh Check for leaks on the desiccant tube caps on tight Check for internal leakage as follows Configure the analyzer for absolute mode measurement Flow CO gt free air through the sample cell and breath into the cool air intake filter Gust below the RS 232C port at the back of the analyzer The displayed CO should not rise by more than a few ppm A sharp rise in the displayed CO coinciding with your breathing indicates a leak A slow increase of 2 to 3 ppm depending on the flow rate of air through the sample cell can be expected due to diffusion of CO through the Bev a line tubing and does not indicate a leak Analyzer Displays CO H20 and or AUX instead of values This indicates an over range condition of the CO2 H20 and auxiliary inputs respectively Analyzer Displays Zero for CO2 or H20 Values e Check the calibration lists FCT 01 and 02 e Check pressure FCT 43 If FCT 73 is set to 43 then pressure is computed from FCTS 71 72 and 44 Otherwise it comes from FCT 77 8 2 Troubleshooting Specifications Type Differential non dispersive infrared gas analyzer HO or CO channels can be independently configured for operation in either differential or absolute mode Detectors Two solid state detectors one each for CO and H3O filtered at 4 26 and 2 59 microns respectively Chopping Frequency 500 hertz Source Single source lifetime gt 10 000 hours Optical Bench One optical be
66. ing H20 Concentration oe eee eeceeseeeeeneeeeecneecaeenaeenes 3 6 3 5 Pressure Broadening Due to Water Vapor eee esse ceseeseceeeees 3 8 3 6 Dilution Corrections c ss s ccsss rsrsr e eene e T EE 3 11 3 7 C is Unknown Measuring C Against Cy 0 oon ceeeeeereesteeeenees 3 12 Section IV Calibration 4 1 Calibration General Information c ccccccccsececeeessseceeecesenteeeees 4 1 4 2 Differential Mode Calibration ccccccsccccceesssececeeesensceeecenensseeees 4 2 4 3 Absolute Mode Calibration 0 cccccccccssssecceceesseececeeessseceeecesenseaeees 4 5 4 4 H20 Absolute Mode Caution ssseeesesesseeeseeseeesrssreresreerrrererresesessene 4 5 4 5 Pressure Corrections c cccccccssssscceceescecceceeseececesessaeceecessececceseaeea 4 9 4 6 Setting the Zero and Span in Software 0 0 eee eee ceecseeeeeeeeees 4 9 4 7 Using the LI 670 Flow Control Unit 0 eee eeeeeeseeeeeseeeneenes 4 12 Section V System Software 5 1 Using the Keypad ooo ee eeeceeeeeeceeseeceeesaecneceaecneseseeeeeeeseeeeeees 5 1 5 2 Software OVELVICW senhonta eierniie EE AE A Eei EEN 5 2 5 3 Console Commands aie n N desaeceeeess oeevaceasuonsbvccsvieiete 5 3 Section VI Interfacing 6 1 General Information peiriers e aae an ES EEEE EEES 6 1 6 2 RS 232C Data Transfer aroc iios ipei renie ari ie 6 2 6 3 Analog Output oss raar ove peronea so rees Opie POSEE IEEE NEEE po EE eri SOE Ps 6 7 6 4 Auxiliary Channel Inputs eeeseeee
67. ing measures 1 Reorient the receiving antenna 2 Relocate the instrument with respect to the receiver 3 Plug the instrument into a different outlet if so equipped so that the instrument and receiver are on different branch circuits If necessary the user should consult LI COR or an experienced radio television technician for additional suggestions The Federal Communications Commission has prepared a booklet entitled How to Identify and Resolve Radio Television Interference Problems which may be helpful to you This booklet stock 004 000 00345 4 is available from the Superintendent of Documents U S Government Printing Office Washington D C 20402 ii NOTICE The information contained in this document is subject to change without notice LI COR MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS MATERIAL INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANT ABILITY AND FITNESS FOR A PARTICULAR PURPOSE LI COR shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing performance or use of this material This document contains proprietary information which is protected by copyright All rights are reserved No part of this document may be photocopied reproduced or translated to another language without prior written consent of LI COR Inc Copyright 1990 LI COR Inc IBM is a registered trademark of International Business Ma
68. ion transmittance v v and analyzer output voltage 1 2 o Vs 1 0 S Vr 0 8 9 Oo Oo Gas Conc j V volts Figure 3 1 A The ratio of detector output while viewing the sample cell v and the reference cell vr decreases with increasing gas concentration B The output voltage V is related to the ratio of Vs to vy by Equation 3 2a Gas concentration in terms of V is the calibration function F V Theory of Operation 3 3 Section 3 The factory calibration of the analyzer consists of measuring the output V at several gas concentrations and determining the coefficients for a fifth order polynomial HO uses a third order polynomial F V that relates V to gas concentration with a zero gas concentration in the reference cell F V aV aV a3V a4V4 a5V gt 3 3 Coefficients a thru as are factory determined for the specific gas and are unique to each analyzer The calibration function F V is only valid for the temperature and pressure at which it was determined and a zero gas concentration in the reference cell It has been found empirically that absolute temperature affects the gas concentration in a linear fashion while pressure affects the signal output V in a linear fashion Therefore the expression relating signal output to gas concentration with a zero gas concentration in the reference cell absolute mode is c vee 3 4 Pt where P is barometric pressure in the cell kPa P is standard barometric
69. is to maintain a low flow of CO gt free air from a compressed tank that goes through the chopper and reference cell and is then vented to the atmosphere Calibration 4 5 Section 4 Figure 4 2 shows one way in which the LI 6262 may be set up with an external pump providing air flow through the reference cell circuit The arrows indicate the direction of air flow through the analyzer It is recommended that the pump be placed inline between the FROM CHOPPER fitting and the scrubber tube assembly rather than between the scrubber tube and the REFERENCE IN fitting Pulling air from the scrubber tube assembly could cause damage to your pump and or analyzer if by chance the paper filter disc in the scrubber tube was torn causing magnesium perchlorate to be pulled into the system Mg ClO4 2 SAMPLE TO IN CHOPPER FROM CHOPPER SAMPLE REFERENCE OUT Figure 4 2 Configuration of LI 6262 with external pump for operation in H2O absolute mode Using the 6262 04 Reference Pump The 6262 04 pumps approximately 0 22 to 0 5 liters of air per minute which is sufficient to purge the reference cell The 6262 04 flow rate can be adjusted with the screwdriver included by turning the Flow Adjust potentiometer clockwise to increase the flow or counterclockwise to decrease the flow Please note also that there is no internal filter ahead of the reference cell Make sure that the paper filter disk in the soda lime desiccant tube is not torn a
70. l code 32 and analyzer temperature channel code 42 through the RS 232C port Data are captured with the 1000 90 COMM program or any other general purpose ASCII capture program 1 Set the communication parameters FCT 17 as follows Baud Rate 4800 Data Bits 8 Stop Bits 2 Parity None This configuration is appropriate for an IBM PC or compatible using the 1000 90 software described in the following section Connect the appropriate cable 2 To test the cable connections and make sure that the computer software is configured properly press FCT 16 which will print a list of the current calibration data for the LI 6262 If nothing is sent make sure that the cable connections are correct and consult the software manual for the software you are using 3 Press FCT 13 and designate 23 32 and 42 as the channels to print 4 Press FCT 15 to print a header after every 20 lines of data are output 5 Press FCT 14 to set the print interval to 1 second 6 The data should look similar to this dac2mm m H2 mm m Temp C 50 000 10 000 21 993 50 000 10 000 21 998 Alternatively to print a single header or one line of data use functions 11 and or 12 as needed after setting the print interval function 14 to zero Interfacing 6 3 Section 6 Using an IBM PC Compatible Computer The 1000 90 Communications and Utility Software included with the LI 6262 will enable the analyzer to interface with any PC compatible computer with an
71. l not to drop the screws onto the LI 6262 circuit boards as damage may occur Follow these steps to replace the soda lime desiccant bottle 7 2 Maintenance Section 7 1 The spare soda lime desiccant bottle in the spare parts kit is shipped without chemicals You will need to procure chemicals locally When handling chem icals observe all manufacturer s safety warnings Viton gasket in lid Polyester fiber in bottle 2 Fill the bottle slightly more than half full with soda lime Fill to the neck with magnesium perchlorate Tap the sides of the bottle to settle the chemicals Insert a polyester fiber wad provided packing firmly This helps keep dust from escaping Make sure the filter disc in the lid is intact replace if necessary Hole in cap 3 Remove the old bottle insert the new bottle into the bottle cover bottom first and reattach the cover to the analyzer Note that there is a small wad of polyester fiber in the bottom of the nickel plated bottle cover to prevent the soda lime desiccant bottle from rattling Nickel plated bottle cover Polyester fiber Magnesium perchlorate is the recommended desiccant since it does not interact with CO Do not use any other desiccant Several grades of magnesium perchlorate are available from commercial suppliers In general the more granular as opposed to powdery the grade the better One type that works well is marketed under the name Dehydrite a
72. ll read and execute the commands sequentially as they are received Any word processor or text editor that can write standard ASCII files is suitable for setting up the configuration file It is important to to save the file in a Text only ASCII only or Non Document mode Here is a simple example of how a command file might be sent to the LI 6262 Prepare the following ASCII file and name it DATA 744 Sets signal averaging time to 4 seconds WL S21 pf Pe OPO LR oO Sets print list 1430 Sets Auto Print to 30 seconds 1510 Sets Auto Header to 10 seconds 762 Turns Vapor Flag to State 2 912123 Sets Display 1 to channel codes 21 and 23 Interfacing 6 5 Section 6 Upload the file from DOS by typing COPY filename COM1 This will copy the contents of the file to the serial port use COM2 if that is the one to which the LI 6262 is connected You may need to reset the communication parameters Baud Rate Parity etc as well using the DOS MODE command Note that you can create a complete configuration file for your LI 6262 by first capturing the data generated using remote command 19 and then editing the file if desired When this file is sent back to the LI 6262 it will configure all elements in its software Using an Apple Macintosh Sending data to the Macintosh requires a Hayes compatible modem cable for the Macintosh Most Hayes modem cables terminate with a male 25 pin D connector that will p
73. lug directly into the LI 6262 In the event that your cable has the wrong gender use a female to female gender changer with pin for pin connections A number of data transfer software programs are commercially available The 1000 91 Communication Software is available free of charge from LI COR Using a Printer The LI 6262 can communicate with virtually any printer having an RS 232C interface One example is the 6000 03B printer from LI COR which is an Epson printer with an RS 232C interface installed The LI 6262 is connected to the 6000 03B printer using the 1000 04 RS 232C cable 6 6 Interfacing Section 6 Solving Communication Problems A few common communication problems and possible causes are given below PROBLEM WHAT TO CHECK Nothing happens Wrong cable Connections tight Handshake All characters are wrong Baud rate set wrong Some characters are wrong Data bits stop bits or parity wrong The most common problem in RS 232C communications is the use of the wrong cable If you have communication problems that cannot be resolved you may wish to purchase an RS 232C indicator card Model 9960 031 This card indicates which lines in the cable are being used and generally indicates where the problem is If the output buffer 512 bytes becomes full the message Too much Data or Baud Rate too low will be displayed This can happen at lower baud rates or if the handshaking XON XOFF or DTR is preventing the data fro
74. m being sent 6 3 Analog Output Analyzer output can be recorded by connecting a logging device to the terminal strip on the back of the analyzer Both linear outputs scaled over any range and in any units and non linear outputs are available Measuring Linear Analyzer Output The LI 6262 has two D A Converters DAC s which can be used to convert calculated quantities your choice of channels 22 27 32 38 or 42 to an analog signal 5V to 5V 100mV to 100mV or 4mA to 20mA ranges The voltage and current ranges are selected by choosing the appropriate terminals on the back panel terminal strip DAC 1 is configured using FCT 05 or FCTS 81 83 and DAC 2 is configured using FCT 06 or FCTS 84 86 A DAC is configured by specifying the source channel e g 22 23 etc which will drive the analog signal the source channel value which Interfacing 6 7 Section 6 corresponds to zero volts or 4mA and the source channel value which corresponds to full scale voltage or 20mA For example to configure DAC 1 to output a voltage signal proportional to differential CO 100 mol mol full scale press FCT 05 and set DAC 1 Code 23 Differential CO channel 1 0V gt O0 Xo zero volts corresponds to 0 Umol mole 1 5V 100 Xp full scale corresponds to 100 umol mole When a voltage range R is selected the DAC output voltage V resulting from a CO differential X is given by R X Xo XF Xo where R 5V or 100mV If
75. n a standard atmosphere The I O Input Output Test checks the Input Output capabilities of the RS 232C port This test requires pins 2 and 3 to be shorted on the RS 232C connector CO2 Zero Span Provides a method to set the CO zero and span in software via the keypad or by sending a remote command sequence See Section 4 5 Setting the Zero and Span in Software for more information System Software 5 9 FCT 08 Reset System The software used in the LI 6262 is also used in the LI 6252 CO analyzer By entering 1 for Yes you can change the configuration to that of a LI 6252 analyzer This function is primarily for factory use only so ordinarily this should not be changed Pressing 1 for Yes will remove all configuration parameters from the analyzer they will then need to be re entered YE NO Reset System FRENG 1 Yes 0 No Clearing EEPROM SYSTEM TYPE Eee LI 62X2 5 6 5 10 System Software FCT 09 09 Integrate This function allows the area under a peak to be computed When you press FCT 09 you are prompted for the following parameters Prompt Description O Source Ch Channel code of the quantity to be integrated On Exit When to start the integration On Exit will start Start Thrsh the integration immediately Thrsh will start the integration when the selected channel rises above the threshold value Thrsh 0 0 If Start Thrsh was selected above you are prompted
76. nal Averaging Time Aux A Auxiliary Input Coefficient A Aux B Auxiliary Input Coefficient B Aux C Auxiliary Input Coefficient C Aux Dest Auxiliary Destination Related Function 61 62 63 64 65 68 Function 77 74 71 72 75 73 There is no remote command for FCT 03 but all of the 7x functions can be accessed remotely System Software 5 5 FCT 04 04 Set Displays Function 04 performs functions 91 99 The LCD display has two lines and each line can be configured to show any channel code 21 29 CO2 31 39 H20 or 41 47 MISC As many as nine two line display configurations can be defined by the Set Displays routine Each display is identified by a number through 9 and can be viewed by pressing the appropriate number without pressing FCT NOTE Displays 1 6 FCT 91 96 default to the configurations shown below at initial power up or system reset Function Codes Display Top Bottom Lines Description 1 21 CO mV non linear 22 CO mol mol absolute 2 23 CO umol mol differential 29 CO umol mol reference 3 41 Temperature mV 42 Temperature C 4 31 H20 mV non linear 32 H20 mmol mol absolute 5 33 H20 mmol mol differential 39 H20 mmol mol reference 6 43 Barometric Pressure kPa 44 Auxiliary mV Set the displays as follows Press FCT followed by 04 The display will show Shows default channel code for top of display 1 Enter new code 21 29 31 39 or 41 47 Default channel code fo
77. nch Sample cell size 0 6 H x 1 3 D x 15 2 cm L 0 25 x 0 5 x 6 0 Volume 11 9 cm Resolution High resolution and sensitivity provided via 16 bit analog to digital converter and user selectable signal averaging time up to 30 seconds set in 1 second increments See individual specifications for CO and H20 Warm up Time 5 minutes Gas Temperature Measured by a thermistor Accuracy 0 5 C 0 60 C Resolution 0 01 C Gas Pressure Maximum allowable pressure is 17 kPa Maximum Flow through Analyzer 10 liters minute Software Features Setup of parameters scaling of analog outputs signal averaging time selection of RS 232C output parameters selection of automatic output of data external control of software via the RS 232C port Program Memory 32K ROM System parameters user entered stored in EEPROM 8K bytes RAM Display 2 line by 16 character backlit LCD with enlarged characters Back panel connections Analog Two channels each having 100 mV 5V and 20 mA full scale 12 bit D A The full range reading can be scaled within these output ranges e g a full range of 350 ppm over 100 mV full scale RS 232C Software selectable parameters baud rates up to 9600 stop bits parity check XON XOFF Non linear CO 0 7500 mV for 0 to 3000 ppm typical 15 000 mV maximum H20 0 4000 mV for 0 to 75 mmol mol typical 15 000 mV maximum Auxiliary Input Output Channel 0 4096 mV Specifications A 1 Keypad 16 key keyp
78. nd is available catalog number C260 M61 from Thomas Scientific P O Box 99 Swedesboro NJ 08085 6099 609 467 2000 See List of Suppliers Appendix B Maintenance 7 3 Section 7 Caution Magnesium perchlorate is a strong oxidizing agent Contact with skin or mucus membranes may cause irritation Avoid bringing it into contact with acids and organic substances such as cotton rubber grain dust etc Consult the container label Figure 7 1 Location of internal soda lime desiccant 7 4 External Soda Lime Desiccant The frequency with which the external soda lime desiccant must be replaced depends greatly on the mode in which the analyzer is operated and how much CO and water vapor it is forced to remove In differential mode with the scrubber tube connected to the chopper ports the soda lime desiccant will need to be changed every 1 4 weeks depending on usage Once the scrubber tube removes the initial CO and water vapor from the circuit it will only need to remove the small amounts of CO and water vapor resulting from tiny leaks and diffusion into the system In absolute mode the soda lime desiccant will degrade more rapidly since it is purging CO and water vapor from the reference cell continuously When measuring H20 in absolute mode the external soda lime desiccant will need to be changed every 24 48 hours of operation For additional information on operating the LI 6262 in this mode refer to Section 4 4 H20 Absolu
79. on Section 4 Sample Ref Sample Aux COz H20 CHO In Ports Diff Scrub Zero Reference CO2 H20 In Scrub LI 670 Scrub both cells Absolute mode Set span 5 Turn OFF the SAMPLE C O H20 Scrub switch Leave the REFERENCE CO H20O Scrub switch ON Adjust the flow as needed 6 Set the LI 6262 span when the displayed reading is steady Sample Ref Sample Aux CO2 H20 Ojo In Ports Diff Scrub Zero Reference COz2 H20 In Scrub LI 670 Scrub only the reference cell The LI 6262 is now ready for use in absolute mode Differential mode operation requires three additional steps Differential mode Set zero 7 Perform steps 1 through 6 and then turn OFF the REFERENCE CO H O Scrub switch Adjust the flow to near that which will be used during measurements 8 Adjust the LI 6262 to read zero when the displayed mole fraction is steady Only a small adjustment should be necessary about 5 ppm when switching from zero to 350 ppm in the reference cell 9 Enter the span gas CO mole fraction in FCT 59 or the span gas HO mole fraction in FCT 68 in the LI COR analyzer Read differential H2O or CO on the analyzer display Check the span by scrubbing the sample cell and looking for zero on FCT 22 or FCT 32 Calibration 4 13 Section 4 Sample Ref Ol ODO Sample Aux CO2 H20 In Ports Diff Scrub Zero Reference In LI 670 Scrub the sam
80. on General Information The factory calibration of the LI 6262 CO2 H2 0 Analyzer consists of determining the coefficients for the calibration polynomials for CO and H20 These coefficients should be quite stable over time but we recommend that they be checked every two years by returning the LI 6262 to LI COR for recalibration The user calibration consists of adjusting the zero and span potentiometers so that the analyzer s output matches the linearization polynomial F V This should be done on a daily basis unless the 6262 03 Pressure Transducer is installed as the span varies with barometric pressure and the zero varies with temperature Figure 4 1 illustrates the effects of the zero and span adjustments 1000 SPAN SHIFT C ppm ZERO SHIFT V volts Figure 4 1 Effects of zero and span adjustments Procedures for zero and span calibrations are given in Section 4 2 for differential mode operation and in Section 4 3 for absolute mode operation Calibration 4 1 Section 4 4 2 Differential Mode Calibration It is important to remember that in differential mode the pressures on the two sides of the analyzer must be kept the same For this reason never connect the exit ports SAMPLE OUT and REFERENCE OUT to anything just vent them to the atmosphere or to tubes of equal length If you wish to flow the same gas through both sides of the analyzer try to avoid doing it by putting the sample and reference cells in series
81. optically identical Strictly speaking of course that is not true This can be illustrated by setting zero with zero gases in both the sample and reference cells and then placing a single span gas in both cells A small zero offset will usually be observed illustrating any minor optical differences between the cells that may exist Nevertheless the treatment given here works very well in practice Small optical anomalies of whatever origin can be corrected empirically by setting zero and span 3 3 Calculating CO Concentration Mole fraction CO C umol mol displayed using FCT 22 comes directly from equation 3 8 The reference concentration value C mol mol should be entered via FCT 59 If the reference air is not dry then c should be the actual CO mole fraction in the presence of water vapor See sections 3 5 and 3 6 CO differential AC umol mol FCT 23 is C C CO partial pressure p Pa displayed using FCT 24 is computed from C and total pressure P kPa by _ cP 1000 Pc The CO weight fraction cg ug g displayed at FCT 26 is computed as where M molecular weight of air g mol weighted for water vapor 29 1 w 1000 18w 1000 w mole fraction of water vapor mmol mol 3 4 Calculating H20 Concentration The calculation of water vapor w mmol mol displayed using FCT 32 is performed using an equation similar to equation 3 8 However we have found that the pressure dependence is different from that u
82. or pathlengths are short 4 This scaling law allows absorption measured under one set of conditions to be scaled to other conditions 2 2 g u P 3 23 Theory of Operation 3 9 Section 3 where A is total band absorption P is total pressure kPa u is absorber amount mol m pL p is mol density mol m3 and L is pathlength m g is a general unspecified function From the ideal gas law the absorber mole density p can be expressed as aP PT RE _ XP RT where p is absorber partial pressure and X is absorber mole fraction mol absorber mol air Therefore XL 3 25 T y lt Substituting equation 3 25 into 3 23 and incorporating the constants L and R into a new function h gives AL gt 3 26 P T In principle equation 3 26 can be solved for mole fraction giving X 3 27 P Since LI COR gas analyzers produce an output voltage that is proportional to absorptance V KA 3 28 substituting 3 28 into 3 27 yields C v2 2 3 29 o where C is the CO mole fraction in umol mol and the constants K Py and To are included in the general function F Po 101 3 kPa and T is the calibration temperature in degrees Kelvin Equation 3 29 is the fundamental 3 10 Theory of Operation Section 3 LI COR gas analyzer calibration function where F x is a polynomial By substituting equation 3 22 into 3 23 and following through the derivation the calibration equations for CO become vawr c p
83. ow rate applications e g eddy correlation or where sample air is particularly dirty you may consider stacking two filters in series For maintenance replace the filter furthest upstream from the analyzer with the filter closest to the analyzer and replace the filter closest to the analyzer with a new filter Air Out Install the new filter s with the blue lettering facing away from the SAMPLE IN or REFERENCE IN ports Instruments with serial numbers of IRG3 239 and below were shipped with internal Balston filters Balston filters have good particle retention with low flow resistance but they equilibrate slowly with changing humidities thus degrading the apparent response time and performance of the LI 6262 Replace the Balston filters with external Gelman filters as described above We recommend that the SAMPLE IN and REFERENCE IN ports be covered with the dust caps provided or attached to an airline when the instrument is not in use This will prevent dust from entering the instrument downstream from the filters where it can enter the optical paths Replacement Gelman Acro 50 filters can be obtained from LI COR part 9967 008 2 4 Absolute vs Differential Mode Operation The LI 6262 may be operated in either absolute or differential modes to simultaneously measure CO and H O in any units The following discussion will help you to set up the analyzer to measure these outputs Setup amp Operation 2 5 Section 2 Prepar
84. ple cell The LI 6262 zero or span can be checked during measurements by turning ON the Diff Zero switch and then using whichever scrubbers are needed Sample Ref Sample Aux CO2 H20 OHO In Ports Diff Scrub Zero Reference In Flow the span gas through both cells of the analyzer Many other calibration variations are possible For example you may want to recirculate air in a closed reference loop for absolute mode operation 4 14 Calibration 5 1 Using the Keypad The LI 6262 uses a 16 key keypad for entering all software function commands and calibration data The keys are arranged as in Figure 5 1 and function as follows FUNCTION Figure 5 1 The LI 6262 Keypad Numeric keys 0 9 and decimal key Used to enter software function codes and calibration numbers Function key Function prompt is accessed allows user to enter any software function command 00 99 Exponent Scroll Up key Used to enter exponents i e when entering CO or H20 calibration numbers or to scroll upward through option lists Minus Scroll Down key Used to enter a negative number sign or to scroll downward through lists Enter key Used to terminate user input from the keypad after entering numbers or to select list entries Clear key Functions as a backspace key deletes last character System Software 5 1 Section 5 5 2 Software Overview All software commands are executed by p
85. r bottom of display 1 1 Bottom 22 NEW _ Prompts to configure displays 2 through 9 follow Press FCT to quit 5 6 System Software FCT 05 06 05 Set D A Conversion 1 Function 05 performs functions 81 82 and 83 Digital to analog conversion NEW __ Digital to Analog Conversions may be performed on channel codes 22 27 32 38 or 42 See function codes 80 83 for further details i x05X low high where x is channel code 22 27 32 38 or 42 06 Set D A Conversion 2 Function 06 performs functions 84 85 and 86 D A Conversion 2 same as NEW __ ij x06X low high where x is channel code 22 27 32 38 or 42 System Software 5 7 FCT 07 08 07 Backlight ON OFF YES or NO BACK LIGHT NO es Press T or J to toggle the LCD display backlight on or off Change if desired depending on the lighting conditions in your work area Continuous use of the backlight may slightly reduce battery operation time NOTE If FCT 07 is executed from the main menu the backlight condition does not change until you exit the menu il O7Y Yes or 07N No 08 Test Menu DISPLAY Test Scrolls through display test menu Teta While most of the items in the Test Menu are for technician use there are a few items of interest to many users The KBD Keyboard Test prompts to press any key each of the 16 keys should display
86. ressing FUNCTION and then entering a two digit function code Some codes execute a function directly while others access scrollable lists of options or other functions any one of which can be selected by pressing ENTER All functions are contained in the main menu by order of function code Decade functions 00 10 20 90 merely serve as entry points to this menu For example pressing FCT 10 will access the menu at 10 from which point T or J can be used to scroll to neighboring functions On the other hand pressing FCT 11 does not access the menu but executes function 11 directly Rapid scrolling down through the menu is done by pressing ENTER while viewing a decade function you will jump to the next decade function e g from 10 to 20 in the menu To illustrate the use of the FUNCTION key and the main menu try this 1 Press FCT 90 The display will show the main menu at 90 as DISP 2 Press to move down one entry to function 91 3 Press ENTER This will select function 91 which shows the channel code that is currently defined for the top line of display 1 and prompts for a new value 4 Press ENTER to retain the displayed value You are prompted to enter a channel code for the bottom line of display 1 Press Enter again to retain the displayed value Note that the display has returned to the menu 5 Press to scroll up to function 90 DISP 6 Press ENTER Selecting a decade function jumps to the next dec
87. roadening and dilution respectively System Software 5 29 FCT 77 78 77 Pressure Barometric Pressure in kPa P kPa NEW __ Barometric pressure must be entered correctly for CO2 or H20 concen trations to be calculated correctly NOTE Barometric pressure may also be input in Setup command 03 Pressure may also be input continuously using the 6262 03 Pressure Transducer from LI COR or through connector 15 on the back panel terminal strip as described in section 6 4 77X where x is the barometric pressure in kPa 78 Vapor Correction a V i l VpCrr A 1 5 apor correction value a NEW __ Vapor correction coefficient a is factory entered a 1 5 See Section 3 5 for a description of the vapor correction This value is only used when Vapor Correct FCT 76 is in State 1 or 2 ij 78a where a is the value of vapor correction a 5 30 System Software FCT 80 80 D A Conversions 80 DAC Enters the menu at function 80 Tabi The digital to analog converter DAC converts a digital value from channels 22 27 32 38 or 42 into a calibrated analog voltage proportional to any units There are two such channels DAC 1 DAC 2 available on the instrument back panel Three output ranges are available for DAC 1 and DAC 2 on the LI 6262 back panel terminal strip 0 5V 0 100 mV and 4 to 20mA To convert voltage output V to the value X t
88. s 6 6 LI 6251manual Equations 6 13 LI 6252 manual or Equations 3 29 LI 6262 manual mV co2 signal in mV Cr reference concentration ppm Tirga Gas temp C Sample Program H 1 vp_r reference cell vapor pressure kPa vp_s sample cell vapor pressure kPa kPa total pressure kPa double Vref gain chi_ws chi_wr eff_cr tc eff_mv result inv_cal tc temp_correction Tirga if Cr 0 0 absolute mode chi_ws chi vp_s kPa eff_mv mV chi_ws p0_over_p kPa result chi_ws cal eff_mv tc return result differential mode chi_wr chi vp_r kPa eff_cr Cr temp_correction Tirga chi_wr inv_cal inverse_cal eff_cr Vref chi_wr inv_cal p0_over_p kPa gain 1 0 Vref K_cal return ppm Vref mV gain 0 Tirga 0 vp_s kPa static double cal double mv The basic irga cal equation polynomial double rtn rtn A_cal B_cal C_cal D_cal E_cal mv mv mv mv mv return rtn H 2 Sample Program static double temp_correction double t return t 273 T_cal 273 static double inverse_cal double cppm returns the mV that would be generated if in absolute mode with cppm in the sample cell double mv_old 0 mv c crude first guess x if water_flag mv cppm 75 5000 else mv cppm 3000 5000 while fabs mv mv_old gt 0 5 mv_old mv c cal mv_old mv mv_old c cppm cal_slope mv_old
89. s magnesium perchlorate can be forced into the reference cell damaging the analyzer Alternatively you can place an external filter between the soda lime desiccant tube and the Reference In fitting M A Phillips head screwdriver is required for installation Follow these steps to install the 6262 04 Reference Pump 1 Remove the soda lime desiccant tube mounting clips from the back of the LI 6262 4 6 Calibration Section 4 Remove the 8 screws from the top and bottom of the 6262 04 cover Attach the 6262 04 cover to the analyzer using the 2 screws from the mounting clips The screws are inserted into the holes where the mounting clips were previously attached Attach the 6262 04 to its cover by replacing the 8 screws Screw the soda lime desiccant tube mounting clips into the rear face plate of the 6262 04 Attach the soda lime desiccant tube Plug the battery cable from the 6262 04 into the battery jack on the analyzer Attach the hoses Mg ClO REFERENCE IN fitting LI 6262 Soda Lime gt TO SCRUB fitting 6262 04 TO CHOPPER fitting LI 6262 REFERENCE OUT fitting LI 6262 This tube is threaded through the 6262 04 FROM CHOPPER fitting 6262 04 FROM CHOPPER fitting LI 6262 The finished assembly will look similar to that shown in Figure 4 3 below Plug battery into the battery jack on the 6262 04 or connect a power cord to the LI 6262 if using AC power Important Note The 6262 04 Referenc
90. sed in equation 3 12 We have found empirically that P P 9 gives more accurate pressure correction than P P Thus 3 6 Theory of Operation Section 3 Ty 273 wory voove 2 Ws 3 12 and 0 9 Vi SaLe pee lea 3 13 T 273 J P For computational speed we make the following approximation 0 9 72 72 jossas 0 1089 ala P P Vapor pressure e kPa FCT 38 is computed from the water vapor mole fraction w and total pressure P kPa wP e 3 15 1000 The dewpoint temperature Tg C FCT 38 is computed from an equation that was fit to the data of Goff and Gratch 1946 as given by List 1966 giving saturation vapor pressure as a function of temperature over a range of 50 to 50 C qy 242627 aie 7 6448 z e where z lo _ eoz and e is vapor pressure in kPa The LI 6262 computes the water vapor weight fraction Wg mg g FCT 36 as Wg 3 17 where M is given after equation 3 12 Theory of Operation 3 7 Section 3 3 5 Pressure Broadening Due to Water Vapor Water vapor can influence infrared detection of CO in three ways 1 direct absorption in the CO2 waveband of interest 2 dilution and 3 pressure broadening Direct infrared absorption by water vapor can be virtually eliminated by judicious choice of wavebands and filters and methods to correct for dilution are well known Section 3 6 however pressure broadening is more of a problem Gas phase absorption o
91. sseeeseseeseseeseerrsreerssrerrsreresresesresreees 6 13 6 5 Temperature OUUTE EEE R ENEE 6 14 6 6 Using the 6262 03 Pressure Transducer eseeesseeeseseeeesreerrereeeeee 6 15 Section VII Maintenance 7 1 Recharging the 6000B and 6200B Batteries 000 eee eects 7 1 7 2 Opening the LI 6262 sirane eerk aa a e E Aie NAE IETT 7 1 7 3 Internal Soda Lime DeSiccant soosnenesonnesesesseeosesesesenessesesersssenreee 7 2 7 4 External Soda Lime Desiccant oosnenessenesosossseneoresesenessesesersssereeee 7 4 WE Bat Dd ASS osc S EE AE SES A EEEE 7 6 DEA E EEEE AE EEE LESSE STAES AEE ADEE OEE 7 6 Section VIII Troubleshooting APPENDIX A Specifications APPENDIX B List of Suppliers APPENDIX C Software Command Index APPENDIX D Channel Code Headers APPENDIX E LI 6262 Console Commands APPENDIX F Saturation Vapor Pressure Table APPENDIX G Connector Descriptions APPENDIX H Sample Program Warranty Unpacking amp a Inspection 1 1 What s What This procedure should be followed if you have just taken delivery on your LI 6262 Check the packing list to verify that you have received everything that was ordered and that you have also received the following items Calibration Sheet This data sheet contains a copy of the calibration information entered into the analyzer at the factory Keep it in a safe place for future reference or in case calibration data must be re entered Console Command Sheet
92. te Mode Caution 7 4 Maintenance Section 7 Fill the tube with equal parts soda lime and magnesium perchlorate separated with a small piece of fiberglass wool as shown in Figure 7 2 below Make sure that the filter paper discs on either end cap are not clogged reduces flow rate or torn Adhesive ringed replacement discs are included in the spare parts kit LI COR part 9960 040 Magnesium perchlorate cannot be regenerated after use Dispose of properly To chopper lt Magnesium Perchlorate Fiberglass Wool Soda Lime From chopper gt Figure 7 2 External soda lime desiccant tube assembly Maintenance 7 5 Section 7 7 5 Fan Filter The external fan filter should be cleaned rinsed out or replaced as needed The filter sits in a recessed cavity in the instrument case and can easily be pulled out with your fingers Two additional external air filters are included in your spare parts kit LI COR part 6560 159 7 6 Fuses There are two fuse holders on the back panel The 1 2 amp slow blow fuse is for 110 VAC line voltage and the 1 4 amp slow blow fuse is for 220 VAC line voltage The 2 amp fast blow fuse is for the external batteries If the LI 6262 fails to turn on check the fuse for the power source you are using battery or AC If the analyzer continually blows fuses it is in need of repair NOTE At 50 Hz 220 VAC it may be necessary to use the 1 2 amp slow blow fuse due to near saturation of th
93. the HzO zero and span is identical to the above steps with the exception that the air must be completely dry to set the zero and the span is set using an airstream containing a known water vapor concentration as can be provided by the LI 610 Portable Dewpoint Generator for example 4 7 Using the LI 670 Flow Control Unit The LI 670 Flow Control Unit can be a valuable accessory for operating and calibrating your LI 6262 The following discussion describes how you can calibrate your LI 6262 using the LI 670 and a single span gas Absolute and Differential Mode Calibration with One Span Gas Absolute mode Set zero 1 Connect the LI 6262 Sample In fitting to the LI 670 Sample Out fitting and the LI 6262 Reference In fitting to the LI 670 Reference Out fitting 2 Enter the station barometric pressure into the LI 6262 at FCT 77 Alternatively you can use the 6262 03 Pressure Transducer or an external sensor to input the barometric pressure 3 Connect a span tank containing air not nitrogen with a known H20 or CO mole fraction to the LI 670 Sample In and Reference In fittings and turn both the reference and sample CO2 H20 Scrub switches ON Use tank pressure to provide flow at a nominal rate near that used during measurements Final flow rate adjustments can be made with the LI 670 SAMPLE and REFERENCE vents 4 When the reading is steady adjust the zero potentiometer on the LI 6262 until the display reads zero 4 12 Calibrati
94. these programs will allow ASCII data sent from the LI 6262 to be displayed on the computer terminal or stored in a disk file 6 4 Interfacing Section 6 Sending Remote Commands to the LI 6262 The 1000 90 software program may also be used to send remote commands to the LI 6262 On the LI 6262 Console Command sheet there is a section entitled remote commands Most LI 6262 commands are duplicated by the remote commands which may be typed on the terminal at any time during the execution of the COMM program even while data are being transmitted Typed characters can be viewed by toggling the F3 key to change to ECHO ON Type the remote commands exactly as they appear on the command sheet For example typing asterisk 1530 will change the Auto Header command to 30 seconds in the LI 6262 The first two digits identify the channel to be edited followed by appropriate arguments for that channel The arguments may be channel numbers calibration values or flags e g Y N depending upon the channel edited If more than one argument is required the first follows the channel identifier without a space or comma and subsequent arguments if any are separated by commas only For example typing 1321 32 33 38 41 will change the print list which is output to your terminal to channel codes 21 32 33 38 and 41 Uploading ASCII Files to the LI 6262 Remote commands can be written in an ASCII file and copied out the serial port The LI 6262 wi
95. tion When using the LI 6262 to measure water vapor in absolute mode note the following When the LI 6262 is configured as described in Section 2 2 for absolute operation air flow created by movement of the chopping shutter disc is sufficient to purge the reference cell of CO2 This air flow is not however sufficient to remove all water vapor present in the reference cell An external pump such as the 6262 04 Reference Pump from LI COR see Using the 6262 04 Reference Pump below or the LI 670 Flow Control Unit is necessary to provide an adequate flow of dry air through the desiccant circuit A flow rate of approximately 500 ml per minute is sufficient to purge the reference cell The flow of dry air through the reference cell and scrubber tube assembly will also greatly affect the performance and maintenance requirements of the external soda lime magnesium perchlorate mixture An inherent property of soda lime is that a small amount of water vapor must be present for the chemical to scrub CO Ordinarily this water vapor is present in the soda lime due to normal diffusion through the air hoses however Mg C104 2 reduces the airstream water vapor concentration to near zero Prolonged exposure of the soda lime to dry air reduces its ability to scrub CO It is therefore recommended that the external soda lime desiccant be replaced every 1 2 days when operating the LI 6262 for absolute H2O measurements If this is a problem an alternative
96. tion in the sample air stream is then corrected to the water vapor mole fraction that is in the reference air stream according to 1 wref 1000 3 33 1 w 1000 wr _ Ws Cs Cs C S is the actual CO mole fraction in the sample cell diluted by w and cY is the equivalent sample cell CO2 mole fraction if it were diluted by Wyeg It is important to distinguish the different water corrections that can be applied in the LI 6262 The Vapor Flag FCT 76 can be in one of three states 0 Corrections Off No pressure broadening or dilution corrections are applied 1 Band Broadening A pressure broadening correction is applied but no dilution correction is performed The actual CO mole fraction in the sample cell or the actual CO gt differential is displayed 2 BndBrd Dil Ref Both a pressure broadening and a dilution correction are applied The sample cell CO2 mole fraction and the CO differential are corrected for differences in sample and reference air stream water vapor contents This is the appropriate setting for photosynthesis measurements NOTE This is the default setting when the system is configured at the factory or when the system is reset FCT 08 3 7 C is Unknown Measuring C against C 0 Sometimes a CO differential must be measured when the reference CO mole fraction is not precisely known For example one might be measuring photosynthesis in the field with ambient air as the reference gas the
97. tion outside the desired band allowing the analyzer to reject the response of other IR absorbing gases The filters are mounted directly on the detectors for thermal stability Each detector is a lead selenide solid state device that is insensitive to vibration The detectors are cooled and regulated to 5 C by thermo electric coolers and electronic circuits continuously monitor and maintain a constant detector sensitivity The result of this detector circuitry is a detector system that is very stable Infrared radiation from the source is focused through the gas cells and onto the detector by a lens at each end of the optical bench Focusing the radiation maximizes the amount of radiation that reaches the detector in order to provide maximum signal sensitivity All of these features provide a CO noise level that is typically 0 3 ppm peak to peak at 350 ppm when using 1 second signal averaging and 1 ppm peak to peak with 0 1 second signal averaging the HzO noise level is approximately 0 002 kPa at 2 0 kPa when using 1 second signal averaging and 0 006 kPa when using 0 1 second signal averaging Signal averaging times are selectable in software between and 30 seconds and are used to achieve even lower noise levels For example with 4 seconds of signal averaging the noise levels typically decrease 50 3 2 Calculating Gas Concentration General LI COR gas analyzers use a lead selenide detector that operates approximately as a lin
98. to enter the starting threshold value Elaps tm the integration to continue until FCT is pressed or Thrsh until a asterisk is received from the remote terminal Elaps tm elapsed time will cause the integration to run for the specified number of seconds Thrsh will cause the integration to continue until the target channel value drops below the threshold NOTE Pressing FCT or receipt of a remote command will always stop the integration Pressing the display keys 1 9 will not stop the integration f buns When to stop the integration Manual will cause Stop Elaps tm s If Stop Elaps tm was selected you are prompted to enter the elapsed time in seconds If Stop Thrsh was selected and Start On Exit you are prompted to enter the threshold value During the integration channel 46 shows the accumulating total area A under the curve as approximated by A XxAt System Software 5 11 FCT 09 where x is the quantity being integrated and At is the time between readings At the end of the integration the non peak area is subtracted according to A At X te t X X 2 where t and t are starting and ending times and X and X are starting and ending values of x Figure 5 2 Channel 46 displays this value which will remain constant until the next integration is started A X Xs b Threshold value Xe k Non pe

LI-6262 CO2/H2O Analyzer Operating and Service Manual

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