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1. Probe L gt Operating uP gt Serial w Menu 4 DOWN Parameters 4 pow Interface DOWN Menu Menu T SET SET SET Cutout BAUD Reset Mode Rate SET EXIT SET EXIT gt gt SET EXIT i Adj Cutout Adjust Ag RO Reset Mode BAUD Rate SET EXIT SET EXIT Sample ALPHA lt Period j lt SET EXIT gt SET EXIT Adj ALPHA SET EXIT SET EXIT T Duplex Mode je SET EXIT Adj Duplex Mode SET EXIT Y Linefeed lt SET EXIT SET EXIT T Interface Option Installed A UP IEEE 488 Calibration Interface DOWN Menu Menu SET Y Device Address SET EXIT gt Adj Device Address I SET EXIT IEEE 488 Option Installed SET Y 5 EXIT Adjust CTO I SET EXIT m x IT o 4 Adjust BO SET EXIT A A DO NOT CHANGE THESE VALUES SEE MANUAL Ci x Adjust BG I SET EXIT 8 2 T B SET EXIT m 5 5 Adjust L
2. 65 lii Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Bath Assembly v ea eee VG xU y EY YS 7 Semi hermetic Compressor 12 Pront Panel ooo sa osse ek Rae EGER GRO XO 21 Back Panel Aco cs SS Bae deus od ep 24 Lid Options 2 6 ose ee 9e uw RO Re 25 Chart of Various Bath 65 33 Controller Operation Flowchart o ses ss pesasse erisa a 38 Bath Temperature Fluctuation at Various Proportional Band Settings 43 Serial Cable Wiring os eo usede 280625 RR xS 52 Sample Calibration 61 13 2 Comments 13 21 EMC Directive Faua era Que ck XD GR Dae cuo Eres cR ARD UR Ge 68 5 Hick ge esos HBOS ead ek SLR 68 13 2 1 Emission Testing ego Roe Ree 69 13 2 2 Low Voltage Directive 69 vi Tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 5 Table 6 Table 7 International Electrical Symbols 1 Temperature Chart se i dex eom M ko 23 TableofBathFluds leen 32 Proportional Band Fluid Table 44 Interface Command 55 Interface Command Summary 56 Serial Power Control Functions
3. 57 Temperature Range Control 58 1 Before You Start Symbols Used 1 1 Before You Start Symbols Used Table 1 lists the International Electrical Symbols Some or all of these symbols may be used on the instrument or in this manual Table 1 International Electrical Symbols Symbol Description No AC Alternating Current AG AC DC Battery CE Complies with European Union Directives MA DC Double Insulated Electric Shock Fuse PE Ground Hot Surface Burn Hazard Read the User s Manual Important Information Off On OPPOUPH 7080 7081 Calibration Bath User s Guide Symbol Description CATI 6 Canadian Standards Association US OVERVOLTAGE Installation CATEGORY II Pollution Degree 2 per IEC1010 1 re fers to the level of Impulse Withstand Voltage protection provided Equipment of OVERVOLTAGE CATEGORY II is energy consuming equipment to be supplied from the fixed installation Examples include household office and laboratory appliances The European Waste Electrical and Electronic Equipment WEEE Directive 2002 96 EC mark Australian EMC Mark 1 2 Safety Information Use this instrument only as specified in this manual Otherwise the protection provided by the instrument may be impaired The following definitions apply to the terms Warning and Caution WARNING identifies conditions
4. 29 Waler op eq od eme eae epe vtta t LAA weak te Bee 29 8 1 10 2 Ethylene Glycol se e epe mre cr Rey Ros Bp ke gl dente 29 8 1 10 3 Methariol CRUS nodes eL Ro SR 29 8 1104 Halocarbo n 8 iu ok Rr Rok ko ie 30 811105 Mineral ex yx Jar Gh Bete cie un 30 8 1 10 6 Silicone oll ew oem Ge ee 30 8 1 11 Fluid Characteristics 30 SILLI Limitations and Disclaimer Ra RR cy een 31 SLI Abut he Graph dee ee Ee Gee xe Yeu dete ke ge 31 SUMING eh GODS ang UR uo EL oed 33 PUMP o saad Gabbe dt ReaD Oe Eee ee eda ERS 33 POWER 2 daar ee oe ee 34 Heater c deg dex ea aS Bee EAE 34 22 42 2220 296 ed XO Ow 9o p we 35 Temperature 35 9 Controller 37 9 1 932 9 3 9 4 9 5 9 6 9 7 9 8 9 9 9 10 BathTemperature lee 37 Reset Cutout 55025 Ad Ay he esp Y eese pU 37 Temperature 39 92921 Programmable 5 39 9 3 2 Setpoint Value uude xo Woe
5. The refrigeration controls are part of the second stage system Depending on the temperature at which the bath is operated the cooling capacity may require adjustment The cooling capacity is controlled using the COOLING ON OFF switch the COOLING POWER HIGH LOW switch and the COOLING TEM PERATURE adjustment valve For typical settings refer to the chart Table 2 on page 23 At higher temperatures typically about 45 C and above the refrigeration is not required as there is sufficient cooling to the room For controlling in this tem perature range switch the COOLING switch to OFF The cooling may be switched on to more quickly lower the bath temperature from a high temperature For maximum cooling and for slewing to and controlling at lower tempera tures the cooling power should be switched to HIGH and the cooling pres sure should be set to 5 to 10 psig Readjust higher or lower as required after the set point temperature is reached Temperature Controller The bath temperature is controlled by Hart Scientific s unique hybrid digi tal analog temperature controller The controller offers the tight control stability of an analog temperature controller as well as the flexibility and programmabil ity of a digital controller The bath temperature is monitored with a platinum resistance sensor in the con trol probe The signal is electronically compared with the programmable refer ence signal amplified and then fed to a puls
6. 12 Maintenance 12 Maintenance The calibration instrument has been designed with the utmost care Ease of op eration and simplicity of maintenance have been a central theme in the product development Therefore with proper care the instrument should require very little maintenance Avoid operating the instrument in dirty or dusty environments A battery is used to maintain operating parameters in the unit All operat ing parameters including calibration parameters should be checked on a regular basis to insure accuracy and proper operation of the instrument See the troubleshooting section for the procedure on checking the status of the battery If the outside of the bath becomes soiled it may be wiped clean with a damp cloth and mild detergent Do not use harsh chemicals on the surface which may damage the paint Periodically check the fluid level in the bath to ensure that the level has not dropped A drop in the fluid level affects the stability of the bath Changes in fluid level are dependent upon several factors specific to the environment in which the equipment is used A schedule cannot be out lined to meet each environmental setting Therefore the first year the bath should be checked weekly with notes kept as to changes in bath fluid Af ter the first year the user can set up a maintenance schedule based on the data specific to the application Heat transfer medium lifetime is dependent upon the type of medium and
7. Hart Scientific 9 7080 7081 Calibration Bath User s Guide Rev 5B2303 Fluke Corporation Hart Scientific Division 799 E Utah Valley Drive American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 E mail support hartscientific com www hartscientific com Subject to change without notice e Copyright 2005 Printed in USA Rev 5B2303 Table of Contents 1 Before You 1 1 symbols Used pre wang Eee UR 1 1 2 Safety Information 2 een 2 1 2 1 WARNINGS c e race acea a y Ba ea x 2 1 2 2 CAUTIONS 4 1 3 Authorized Service 5 2 Introduction 7 3 Specifications and Environmental Conditions 9 3 1 2 24 9 3 2 Environmental Conditions 9 3 3 Warranty 5 10 4 Quick Start uou eor x ROO OR RR x MI 4 1 Unpacking 5 2 iua eee hae 11 4 2 Semi Hermetic Compressor leen 11 4 3 Set Up ua ERG EU Max moe vega 11 44 PoWet BO RE S C RR de S ROUGE a 12 4 5 Setting the 13 5 Installation 15 5 1 Bath Environment 4 24k cx 9
8. 40 9 3 3 Setpoint Vefbler s esq tei BA ast pa RBS 40 Temperature Scale 80 41 Secondary 2 22 22 2 4 42 Heater POWEL GAS BES Ge 42 Proportional 42 CUOU Ar ccr 45 Controller Configuration 46 Probe Parameters 46 9 10 1 xc ce Rm OAR Ee PERO ae ES por Rea due ers 46 9 10 2 ALPHA 2 an creed sie NO P Rr RNC Ge i see 47 911 Operating Parameters os ys o gi lees 47 9 11 1 Cut out Reset 47 9 12 Serial Interface Parameters 47 9 12 1 BAUD Rate 1303 gh eal s Oh et rud RON AG 47 9 12 2 Sample Period sca ouk cue m ven VR e geb OX Du e Wd d 48 9 12 3 Duplex Mode s tpe US DR AEEA ees 48 9 12 4 a oe 49 9 13 IEEE 488 Parameters 49 9 13 1 Address 406a A Re a 49 9 14 Calibration Parameters 50 9 14 1 CIO ebb ose ek eee He SEES OS 50 9 14 2 BO end BG 52225255 4555 WES Rs eue SOR HERES 50 9 14 3 Ee CHE hs e at RS 50 10 Digital Communication Interface 51 10 1 Serial Communications 51 10 1 1 25544 de hne b x cede d
9. 46 9 9 9 10 9 10 1 Decrement display CO 95C i New cut out set point To accept the new cut out set point press SET SET Accept cut out set point The next function is the configuration menu Press EXIT to resume display ing the bath temperature Controller Configuration The controller has a number of configuration and operating options and calibra tion parameters which are programmable via the front panel These are ac cessed from the secondary menu after the cut out set point function by pressing SET There are 5 sets of configuration parameters probe parameters oper ating parameters serial interface parameters IEEE 488 interface parameters and controller calibration parameters The menus are selected using the UP and DOWN keys and then pressing SET Probe Parameters Menu The probe parameter menu is indicated by PrQbE i Probe parameters menu Press SET to enter the menu The probe parameters menu contains the pa rameters RO and ALPHA which characterize the resistance temperature rela tionship of the platinum control probe These parameters may be adjusted to improve the accuracy of the bath This procedure is explained in detail in Sectionll The probe parameters are accessed by pressing SET after the name of the pa rameter is displayed The value of the parameter may be changed using the UP and DOWN buttons After the desired value is reached press SET
10. x 10 7 25 x 12 75 call for custom sizes 127 x 254 mm 184 x 324 mm Depth 12 305 mm 13 25 337 mm Wetted Parts 304 stainless steel Power 230 VAC 10 50 or 60 Hz 13 A single phase 2900 W specify fre quency Volume 7 2 gallons 27 liters 11 2 gallons 42 liters Weight 350 Ib 159 kg Size 46 H x 30 5 W x 19 D 1168 x 775 x 483 mm Automation Package Interface it software and an RS 232 computer interface are available for setting the bath temperature via an external computer For IEEE 488 add 2001 IEEE to the automation package Safety OVERVOLTAGE Installation CATEGORY Il Pollution Degree 2 per IEC1010 1 Environmental Conditions Although the instrument has been designed for optimum durability and trou ble free operation it must be handled with care The instrument should not be operated in an excessively dusty or dirty environment Maintenance and clean ing recommendations can be found in the Maintenance Section of this manual The instrument operates safely under the following conditions 7080 7081 Calibration Bath User s Guide 3 3 e temperature range 5 50 C 41 122 F e ambient relative humidity maximum 8046 for temperature 31 C de creasing linearly to 50 at 40 C e pressure 75kPa 106kPa e mains voltage within 10 of nominal e vibrations in the calibration environment should be minimized e altitude less than 2 000 meters Warranty Fluke
11. 63 7080 7081 Calibration Bath User s Guide 64 12 1 plicable to all fluids used in the baths should be kept in close proximity to the instrument If the mains supply cord becomes damaged replace it with a cord with the appropriate gauge wire for the current of the bath If there are any questions call an Authorized Service Center for more information Before using any cleaning or decontamination method except those rec ommended by Hart users should check with an Authorized Service Cen ter to be sure that the proposed method will not damage the equipment If the instrument is used in a manner not in accordance with the equip ment design the operation of the bath may be impaired or safety hazards may arise The over temperature cut out should be checked every 6 months to see that it is working properly In order to check the user selected cut out fol low the controller directions Section 9 8 for setting the cut out Both the manual and the auto reset option of the cut out should be checked Set the bath temperature higher than the cut out Check to see if the display flashes cut out and the temperature is decreasing A CAUTION When checking the over temperature cut out be sure that the temperature limits of the bath fluid are not exceeded Exceeding the tem perature limits of the bath fluid could cause harm to the operator lab and instrument Draining the Bath The drain is located on the back of the bath See
12. Figure 6 Chart of Various Bath Fluids 8 2 Stirring Stirring of the bath fluid is very important for stable temperature control The fluid must be mixed well for good temperature uniformity and fast controller response The stirrer is precisely adjusted for optimum performance 8 3 Pump The bath may have the optional pump lid for recirculating bath fluid through equipment outside the bath Be sure the hoses are fastened securely to the pump inlet and outlet tubes before operating the bath with the pump lid Always use 33 7080 7081 Calibration Bath User s Guide 34 8 4 8 5 tubing with material properties consistent with the application considering chemical and temperature compatibility The centrifugal pump may develop 5 psi of pressure To maximize the flow rate use hoses with 1 2 in or greater ID Maximum flow rate may be approximately 8 gal min Temperature control stability can be expected to be less with the recirculation pump Insulating the fluid hoses may be required at low bath temperatures to reduce warming of the fluid and to prevent condensation or icing around the hoses The refrigeration may require adjustment to optimize performance If heat flux to the recirculated fluid is excessive the bath may not be able to achieve the lowest temperatures Power Power to the bath is provided by an AC mains supply of the appropriate voltage to power the bath Refer to the Specifications section for power details Refe
13. the environment The fluid should be checked at least every month for the first year and regularly thereafter This fluid check provides a baseline for knowledge of bath operation with clean usable fluid Once some fluids have become compromised the break down can occur rapidly Particular attention should be paid to the viscosity of the fluid A significant change in the viscosity can indicate that the fluid is contaminated being used out side of its temperature limits contains ice particles or is close to a chemi cal breakdown Once data has been gathered a specific maintenance schedule can be outline for the instrument Refer to the General Operation section Section 8 for more information about the different types of flu ids used in calibration baths Depending on the cleanliness of the environment the internal parts parts behind the front cover only of the cold bath should be cleaned and or checked at least every month for dust and dirt Particular attention should be paid to the condensing coil fins The fins should be vacuumed or brushed free of dust and dirt on a regular basis Dust and dirt inhibit the operation of the condensing coil and thus compromise the performance and life time of the cooling system If a hazardous material is spilt on or inside the equipment the user is re sponsible for taking the appropriate decontamination steps as outlined by the national safety council with respect to the material MSDS sheets ap
14. to set the parameter to the new value Pressing EXIT causes the parameter to be skipped ignoring any changes that may have been made RO This probe parameter refers to the resistance of the control probe at 0 C Nor mally this is set for 100 000 ohms 9 Controller Operation Operating Parameters 9 10 2 9 11 9 11 1 9 12 9 12 1 ALPHA This probe parameter refers to the average sensitivity of the probe between 0 and 100 C Normally this is set for 0 00385 C Operating Parameters The operating parameters menu is indicated by PAr i Operating parameters menu Press SET to enter the menu The operating parameters menu contains the cut out reset mode parameter Cut out Reset Mode The cut out reset mode determines whether the cut out resets automatically when the bath temperature drops to a safe value or must be manually reset by the operator The parameter is indicated by Cut out reset mode parameter Press SET to access the parameter setting Normally the cut out is set for manual mode Serial Interface Parameters The serial RS 232 interface parameters menu is indicated by SEcIRL Serial RS 232 interface parameters menu The serial interface parameters menu contains parameters which determine the operation of the serial interface These controls only apply to baths fitted with the serial interface The parameters in the menu are BAUD rate sample pe riod duplex mode and
15. 7 5 213 247 VAC Authorized Service Centers Please contact one of the following authorized Service Centers to coordinate service on your Hart product Fluke Corporation Hart Scientific Division 799 E Utah Valley Drive American Fork UT 84003 9775 USA Phone 1 801 763 1600 Telefax 1 801 763 1010 E mail support hartscientific com Fluke Nederland B V Customer Support Services Science Park Eindhoven 5108 5692 EC Son NETHERLANDS 7080 7081 Calibration Bath User s Guide Phone 31 402 675300 Telefax 31 402 675321 E mail ServiceDesk G fluke nl Fluke Int l Corporation Service Center Instrimpex Room 2301 Sciteck Tower 22 Jianguomenwai Dajie Chao Yang District Beijing 100004 PRC CHINA Phone 86 10 6 512 3436 Telefax 86 10 6 512 3437 E mail xingye han fluke com cn Fluke South East Asia Pte Ltd Fluke ASEAN Regional Office Service Center 60 Alexandra Terrace 03 16 The Comtech Lobby D 118502 SINGAPORE Phone 65 6799 5588 Telefax 65 6799 5588 E mail antng C singa fluke com When contacting these Service Centers for support please have the following information available Model Number e Serial Number e Voltage e Complete description of the problem 2 Introduction Introduction The Hart Scientific Model 7080 7081 is a very precise constant temperature bath The bath is specially designed for low temperature applications An inno vative state of the art solid
16. Corporation Hart Scientific Division Hart warrants this product to be free from defects in material and workmanship under normal use and service for a period as stated in our current product catalog from the date of shipment This warranty extends only to the original purchaser and shall not apply to any product which in Hart s sole opinion has been subject to misuse alteration abuse or abnormal conditions of operation or handling Software is warranted to operate in accordance with its programmed instruc tions on appropriate Hart products It is not warranted to be error free Hart s obligation under this warranty is limited to repair or replacement of a product which is returned to Hart within the warranty period and is determined upon examination by Hart to be defective If Hart determines that the defect or malfunction has been caused by misuse alteration abuse or abnormal condi tions or operation or handling Hart will repair the product and bill the pur chaser for the reasonable cost of repair To exercise this warranty the purchaser must forward the product after calling or writing an Authorized Service Center for authorization see Section 1 3 The Service Centers assume NO risk for in transit damage THE FOREGOING WARRANTY IS PURCHASER S SOLE AND EXCLU SIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTIES EX PRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OR MERCHANTABILITY OR FITNESS FOR ANY PARTICUL
17. Menu Read proportional band setting f f Set proportional band to n Depends on Configuration Read cutout setting c utout 9999 x xxx Set cutout setting c utout n r eset Set cutout to n degrees c utout n Temperature Range Reset cutout now c utout r eset Read heater power po wer duty cycle Configuration Menu Probe Menu Read RO calibration parameter Set RO calibration parameter to n e Read ALPHA calibration parameter al pha Set ALPHA calibration parameter to n al pha n 00370 to 00399 Operating Parameters Menu Read cutout mode cm Set cutout mode cm ode r eset a uto N RESET or AUTO Set cutout to be reset manually cm ode r eset f Set cutout to be reset automatically cm ode a uto Serial Interface Menu Read serial sample setting sa mple sa sa 9 sa 1 Set serial sampling setting to n seconds sa mple n sa 0 Set serial duplex mode du plex f ull h alf Set serial duplex mode to full du plex f ull Set serial duplex mode to half du plex h alf Set serial linefeed mode If eed on of f Set serial linefeed mode to on If eed on Set serial linefeed mode to off Iffeed of f Calibration Menu 55 7080 7081 Calibration Bath User s Guide Interface Command Summary Continued Command Command Returned Acceptable Co
18. a 6 digit num ber with five digits after the decimal point This is a temperature offset in de grees of the selected units C or F 0 00000 Current vernier value in C To adjust the vernier press UP or DOWN Unlike most functions the ver nier setting has immediate effect as the vernier is adjusted SET need not be pressed This allows one to continually adjust the bath temperature with the vernier as it is displayed Increment display 9 Controller Operation Temperature Scale Units 9 4 0 00090 New vernier setting Next press EXIT to return to the temperature display or SET to access the temperature scale units selection SET Access scale units Temperature Scale Units The temperature scale units of the controller may be set by the user to degrees Celsius C or Fahrenheit F The units will be used in displaying the bath temperature set point vernier proportional band and cut out set point The temperature scale units selection is accessed after the vernier adjustment function by pressing SET From the temperature display function access the units selection by pressing SET 4 times 25 00 C Bath temperature Unz C i Scale units currently selected Press UP or DOWN to change the units Change units 41 7080 7081 Calibration Bath User s Guide 42 9 5 9 6 9 7 New units selected Press SET to accept the new selection and resume
19. and 0 0038500 respectively and the data for t ty and erry were as given above then the new values RO and ALPHA would be computed as 99 885 and 0 0038302 re spectively Program the new values Ry and ALPHA into the controller Check the calibration by setting the temperature to tj and ty and measuring the errors again If desired the calibration procedure may be repeated again to further im prove the accuracy Calibration Example The bath is to be used between 25 and 75 C and it is desired to calibrate the bath as accurately as possible for operation within this range The current val ues for RO and ALPHA are 100 000 and 0 0038500 respectively The calibra tion points are chosen to be 30 00 and 80 00 C The measured bath 11 Calibration Procedure Calibration Example temperatures are 29 843 and 79 914 C respectively Refer to Figure 10 for ap plying equations to the example data and computing the new probe constants RO 100 000 ALPHA 0 0038500 tj 30 00 C measured t 29 843 C ty 80 00 C measured t 79 914 C Compute errors erry 29 843 30 00 0 157 C errg 79 914 80 00 C 0 086 C Compute Ro RO 0 086 x 30 0 0 157 x 80 0 80 0 30 0 0 00385 1 100 077 Compute ALPHA ALPHA 0 00385 x 80 0 0 157 1 0 00385 x 30 0 0 086 0 00385 0 0038416 80 0 30 0 Figure 10 Sample Calibration Computations 61
20. linefeed BAUD Rate The BAUD rate is the first parameter in the menu The BAUD rate setting de termines the serial communications transmission rate 47 7080 7081 Calibration Bath User s Guide 48 9 12 2 9 12 3 The BAUD rate parameter is indicated by BAU Serial BAUD rate parameter Press SET to choose to set the BAUD rate The current BAUD rate value will then be displayed i200 b Current BAUD rate The BAUD rate of the bath serial communications may be programmed to 300 600 1200 or 2400 BAUD Use UP or DOWN to change the BAUD rate value 2400 b i New BAUD rate Press SET to set the BAUD rate to the new value or EXIT to abort the op eration and skip to the next parameter in the menu Sample Period The sample period is the next parameter in the serial interface parameter menu The sample period is the time period in seconds between temperature measure ments transmitted from the serial interface If the sample rate is set to 5 the bath transmits the current measurement over the serial interface approximately every five seconds The automatic sampling is disabled with a sample period of 0 The sample period is indicated by SAMPLE ME Serial sample period parameter Press SET to choose to set the sample period The current sample period value is displayed SR Current sample period seconds Adjust the value with UP or DOWN and then use SET to set the sample
21. properly the control ler immediately begins transmitting temperature readings at the programmed rate The set point and other commands may be sent to the bath via the serial interface to set the bath and view or program the various parameters The inter face commands are discussed in Section IEEE 488 Communication optional The IEEE 488 interface is available as an option Baths supplied with this op tion may be connected to a GPIB type communication bus which allows many instruments to be connected and controlled simultaneously To eliminate noise the GPIB cable should be shielded Setup To use the IEEE 488 interface first connect an IEEE 488 standard cable to the back of the bath Next set the device address This parameter is programmed within the IEEE 488 interface menu The IEEE 488 interface parameters menu is outlined in Figure 7 53 7080 7081 Calibration Bath User s Guide 54 10 2 1 1 10 2 2 10 3 10 4 To enter the IEEE 488 parameter programming menu first press EXIT while pressing SET and release to enter the secondary menu Press SET repeat edly until the display reaches Pr Gb E This is the menu selection Press UP repeatedly until the IEBE 488 interface menu is indicated with IE E E Press SET to enter the IEEE 488 parameter menu The IEEE 488 menu contains the IEEE 488 address parameter IEEE 488 Interface Address The 488 address is prompted with Addr E55 Pres
22. slush which effectively increases the vis cosity and reduces temperature stability Pumping systems may be rendered in effective due to ice blockage The ice water can be removed occasionally by heating the fluid up to 100 C for brief periods of time Use halocarbon 0 8 un der a fume hood at higher temperatures to remove vapors Toxicity is low but caution is always recommended Halocarbon 0 8 has excellent electrical resis tivity This fluid is fairly expensive Mineral Oil Mineral oil or paraffin oil is often used at moderate temperatures above the range of water Mineral oil is relatively inexpensive At lower temperatures mineral oil is quite viscous and control may be poor At higher temperatures vapor emission becomes significant The vapors may be dangerous and use of a fume hood is highly recommended As with most oils mineral oil expands as temperature increases so be careful not to fill the bath too full that it overflows when heated The viscosity and thermal characteristics of mineral oil are poorer than water so temperature stability is not as good Mineral oil has very high electrical resistivity Use caution with mineral oil since it is flammable and may also cause serious injury if inhaled or ingested Silicone oil Silicone oils are available which offer a much wider operating temperature range than mineral oil Like most oils silicone oils have temperature control characteristics which are somewhat poorer than water Th
23. state temperature controller has been incorporated which maintains the bath temperature with extreme stability The controller uses a microprocessor to execute the many operating functions y w Figure 1 Bath Assembly 7080 7081 Calibration Bath User s Guide User interface is provided by the 8 digit LED display and four key switches Digital remote communications is optionally available with a RS 232 or IEEE 488 interface The tank for the 7080 7081 1s stainless steel The 7080 holds 25 liters and the 7081 holds 44 liters There are two lids available the standard lid with a rectan gular access hole and an optional lid with a recirculation pump see Figure 5 3 Specifications and Environmental Conditions Specifications 3 1 3 2 Specifications and Environmental Conditions Specifications 7080 7081 Range 80 C to 110 C Stability 0 0025 C at 80 C methanol 0 0015 C at 0 C methanol 0 0015 C at 25 C water 0 003 at 100 C Uniformity 0 007 C at 80 C methanol 0 005 C at 0 C methanol 0 003 C at 25 C water 0 005 C at 100 C oil Temperature Setting Digital display with push button data entry Set Point Resolution 0 01 C high resolution mode 0 00007 C Display Resolution 0 01 C Digital Setting Accuracy 1 C Digital Setting Repeatability 0 01 C Heaters 500 and 1000 Watts Access Opening 5
24. temperatures tends to condense and absorb water from the air This is generally an advan tage however since small amounts of water less than 11 mixed with metha nol decreases the freezing point The resulting low temperature capability can be well below 100 C but the viscosity can become excessive at such low tem peratures The viscosity is quite acceptable from 80 C up A mixture of 50 50 methanol and water provides a non flammable solution capable of attaining 40 C Because methanol has an infinite capability to absorb water there is no ice 29 7080 7081 Calibration Bath User s Guide 30 8 1 10 4 8 1 10 5 8 1 10 6 8 1 11 formation below 0 C This is convenient for long term use The mixture has poor electrical resistivity and so may not be suitable for some applications The primary disadvantage with methanol is its toxicity It is also quite flamma ble Some labs may not permit its use Refer to the MSDS sheets for more in formation Use methanol only in a well ventilated area and use a hood that draws the vapors away from the user at temperatures above 0 C Halocarbon 0 8 Halocarbon 0 8 is a low temperature fluid with a wide temperature range It may be used as low as 90 to 100 C before viscosity becomes too great It may be used as high as 70 C before evaporation becomes excessive Halocarbon 0 8 does not absorb water and forms ice at temperatures below 0 C Ice crystals turn the fluid into a
25. the access hole cover from the bath and check the tank for foreign matter dirt remnant packing material etc Use clean unpolluted fluid Care fully fill the bath through the large square access hole to a level that will allow for stirring and thermal expansion The fluid should never exceed a height of 1 2 below the top of the tank Carefully monitor the bath fluid level as the bath temperature rises to prevent overflow or splashing Remove excess fluid if nec essary and with caution if the fluid is hot Be careful to prevent bath fluid from spilling on the stirring motor while filling Note that underfilling may reduce bath performance and may possibly damage the bath heater Probe Inspect the bath control probe It should not be bent or damaged in any way Reasonable caution should be used in handling this probe as it contains a preci sion platinum sensor and is mechanically shock sensitive Dropping striking or other physical shock may cause a shift in resistance in the probe resulting in diminished bath accuracy If damaged the probe can be replaced Contact the factory for assistance Insert the probe into the 1 4 inch probe hole at the top left side of the bath lid The tip of the probe must be well immersed in the fluid The probe connector is plugged into the rear of the bath into the socket labelled PROBE Power With the bath power off connect the bath to an AC mains supply of the appro priate voltage to power th
26. to maintain Fuming is excessive Excessive amounts of heater power may be required because of the heat of vaporization Decomposition high temperature fluids may reach a temperature point at which decomposition of some form will begin While it always begins slowly at some lower temperature the rate can increase to the point of danger or imprac ticality at a higher temperature 32 8 General Operation Stirring 100 0 100 C 200 C 300 C 400 C 500 C 600 C Silicone Oil 5017 FL 302 C Silicone Oil FL 280 C 5014 PN Silicone Oil 5013 FL 232 C 4 Silicone Oil 5012 m FL 211 C Silicone Oil 5010 FL 133 C HFE 7500 5023 Halocarbon 5019 Mineral Oil 5011 Water Methanol Ethanol FL 16 C Ethylene Glycol 50 50 with H20 5020 Dynalene HF LO 5001 _ _ E Decomposition Starts nu BP Legend Shaded area represents usable range of fluid starting at BP Boiling Point 50 centistokes Lighter shading represents decreasing CS Centistokes viscosity while vaporization and decomposition increase fi RE anon Point uid loss Saaz Black area represents liquid range with excessive dusiiolevaporaticn FL Flash Point viscosity FR Freeze Point PP Pour Point Range over which a fume hood is recommended
27. turn the bath on using the front panel POWER switch The bath will turn on and begin to heat or cool to reach the previously programmed temperature setpoint The front panel LED display will indicate the actual bath temperature 4 Quick Start Setting the Temperature 4 5 Setting the Temperature In the following discussion and throughout this manual a button around the word SET UP EXIT or DOWN indicates the panel button while the dotted box indicates the display reading Explanation of the button or display reading are to the right of each button or display value To view or set the bath temperature set point proceed as follows The front panel LED display normally shows the actual bath temperature 24 68 C Bath temperature display When SET is pressed the display shows the set point memory that is cur rently being used and its value Eight set point memories are available SET Access set point selection I 250 Set point 1 25 09 currently used Press SET to select this memory and access the set point value SET Access set point value t 2500 Current value of set point 1 25 00 C Press SET to accept the new value and display the vernier value The bath be gins heating or cooling to the new set point SET Store new set point access vernier 0 00000 Current vernier value 13 7080 7081 Calibration Bath User s Guide 14 The bath heats or cools until it reaches the new set poin
28. 25 C 0 00108 1000 25 C 200 10 5012 3 135 C 0 45 100 C 50 150 C 0 482 200 C Silicone Oil Type 10 C v 230 C fl 232 C 20 25 C 0 949 25 C 0 370 0 40 C 0 00034 25 C 0 00107 1000 25 C 200 20 5013 0 393 100 C 50 150 C 0 420 200 C Silicone Oil Type 30 C v 278 C fl 280 C 50 25 C 0 96 25 C 0 4 0 00037 25 C 0 00104 1000 25 C 200 50 5014 50 150 C Silicone Oil Type 70 C v 230 C fl 232 C 50 70 C 1 07 25 C 0 358 40 C 0 00035 25 C 0 00075 100 25 550 5016 300 C fl 10 104 C 0 386 100 C 1 150 C 0 433 200 C Silicone Oil Type 80 C v 300 C fl 302 C 50 80 C 1 11 25 C 0 363 40 C 0 00035 25 C 0 00077 100 25 710 5017 7 8 204 C 0 454 100 C 1 150 C 0 505 200 C Silicone Oil Type 66 C v 313 C fl 315 C 50 66 C 0 96 25 C 0 34 100 C 0 0003 0 00095 100 25 C 210 H 14 204 C 1 150 C Heat Transfer Salt 180 fr 550 C NONE 34 150 C 2 0 150 C 0 33 0 0014 0 00041 1 7 lem 5001 6 5 300 C 1 9 300 C 2 4 500 C 1 7 500 C Limiting Factors b boiling point high evaporation fl flash point fr freeze point v viscosity Flash point test oc open closed cup Very low water solubility ice will form as a slush from condensation below freezing Boiling Point At the boiling point of the fluid the temperature stability is diffi cult
29. 4 The control indicator is a two color light emitting diode LED This in dicator lets the user visually see the ratio of heating to cooling When the indicator is red the heater is on and when it is green the heater is off and the bath is cooling 5 The heater power switch is used to select the appropriate heater power levels for heating and controlling temperatures 6 The cooling switch controls power to the cooling compressors and cool ing fan Refrigeration Controls The front panel refrigeration control area has four features see Figure 3 on page 21 7 the cooling power switch 8 the cooling temperature regulating valve 9 the cooling temperature pressure gauge and 10 cascade refrigeration indicator lights 7 The cooling power switch is used to control the cooling capacity It is set to LOW power for higher bath temperatures 40 C and above This switch limits the capacity of the refrigeration system so that the mini mum cooling power is used for the greatest temperature stability 8 The cooling temperature regulating valve is used to adjust the tempera ture at which the refrigerant evaporates Refer to the label below the gauge for approximate pressure and evaporative temperature settings For your convenience the table from the label is reproduced below Table 2 Do not set the pressure higher than indicated for the desired bath temperature 9 The cooling temperature pressure gauge is used to indicate the
30. AR PURPOSE OR USE HART SHALL NOT BE LIABLE FOR ANY SPECIAL INDIRECT INCIDENTAL OR CONSEQUENTIAL DAM AGES OR LOSS WHETHER IN CONTRACT TORT OR OTHERWISE 4 Quick Start Unpacking 4 4 1 4 2 4 3 Quick Start A CAUTION Before placing the bath in service READ SECTION 6 ENTI TLED BATH USE Incorrect handling can damage the bath and void the warranty This chapter gives a brief summary of the steps required to set up and operate the 7080 or 7081 bath This should be used as a general overview and reference and not as a substitute for the remainder of the manual Please read Sections5 through8 carefully before operating the bath Unpacking Unpack the bath carefully and inspect it for any damage that may have oc curred during shipment If there is shipping damage notify the carrier immediately Verify that all components are present e 7080 7081 Bath e Access Hole Cover e Controller Probe e Manual e Drain Elbow e Report of Test e Fill Hole Cover e 9930 Interface it Software and User s Guide optional If you are missing any item please contact an Authorized Service Center see Section 1 3 Semi Hermetic Compressor The semi hermetic compressor s located below the bath have had their mounting hardware tightened down to avoid damage during shipment In addi tion shipping foam has been placed between some of the refrigeration lines for the same purpose Upon installation please remove all pieces of the shi
31. Cutout 1 2 2 CAUTIONS To avoid possible damage to the instrument follow these guidelines Always operate this instrument at room temperature between 41 F and 122 F 5 C to 50 C Allow sufficient air circulation by leaving at least 6 inches 15 cm of clearance around the instrument When filling the tank ensure the immersion coils are completely covered DO NOT overfill the bath Overflowing fluid may damage the electrical system See Section 5 3 Bath Preparation and Filling for specific instruc tions Read Section 6 Bath Use before placing the bath into service DO NOT turn the bath on without fluid in the tank and the heating coils fully immersed DO NOT change the values of the bath calibration constants from the fac tory set values The correct setting of these parameters is important to the safety and proper operation of the bath The refrigeration may be damaged or the lifetime shortened if the set point temperature is set above 60 C for more than one hour with the refrigeration manually on Ensure that the refrigeration is off when the bath is used above 60 C The Factory Reset Sequence should be performed only by authorized personnel if no other action is successful in correcting a malfunction You must have a copy of the most recent Report of Test to restore the test pa rameters DO NOT operate this instrument in an excessively wet oily dusty or dirty environment Most probes have handle tempera
32. Figure 4 Back Panel Locate the drain plug on the end of the drain tube This drain plug is to be fluid tight until the bath is drained The following information is helpful when draining the bath 1 Always use container capable of holding the entire load of fluid Use safety equipment as appropriate Drain water and low viscosity fluids at room temperature Normal care must be taken for fluids that may have corrosive or damaging effects on the surrounding facility or equipment High viscosity oils should be sufficiently low in viscosity to drain effec tively Some oils such as 710 silicone oil may need to be heated to 80 C to drain well The viscosity affects how rapidly it drains as well as how well it flows off of the walls Appropriate temperature resistant contain ers and appropriate safety equipment such as face shields gloves and body covering should be used 13 Troubleshooting Troubleshooting 13 13 1 Troubleshooting In the event the bath appears to function abnormally this section may help to find and solve the problem Several possible problem conditions are described along with likely causes and solutions If a problem arises please read this sec tion carefully and attempt to understand and solve the problem If the bath seems faulty or the problem cannot otherwise be solved then contact an Autho rized Service Center for assistance Troubleshooting Problem Causes and Solutions The bath do
33. GH to enable remote control Adjust the cool ing temperature to the lowest temperature desired Digital Interface Setup front panel controls HEATER switch LOW COOLING switch OFF COOLING POWER switch HIGH COOLING TEMPERATURE 5 psi Serial Communications The bath may be installed with an RS 232 serial interface that allows serial dig ital communications over fairly long distances With the serial interface the user may access any of the functions parameters and settings discussed in Section9 with the exception of the BAUD rate setting Wiring The serial communications cable attaches to the bath through the DB 9 connec tor at the back of the instrument Figure 9 shows the pin out of this connector and suggested cable wiring To eliminate noise the serial cable should be shielded with low resistance between the DB 9 connector and the shield Setup Before operation the serial interface of the bath must first be set up by pro gramming the BAUD rate and other configuration parameters These parame ters are programmed within the serial interface menu The serial interface parameters menu is outlined in Figure 7 on page 38 To enter the serial parameter programming mode first press EXIT while pressing SET and release to enter the secondary menu Press SET repeat edly until the display reads Pr ob E This is the menu selection Press UP 51 7080 7081 Calibration Bath User s Guide R
34. Re RE 15 5 2 Drysout Period uu adea y ORAN WS E 15 3 3 Bath Preparation and Filling 15 5 4 s s Gods UIS VE ITE 16 222 POWef 55228 SERED OS 4 TS 16 6 Bath 5 2 2 22222655 44 55 ve 19 6 1 General 26h aka ye ee 19 6 2 Comparison 19 6 3 Calibration of Multiple Probes 20 7 21 7 1 Front Panel s soss ac maci ee 21 7 2 Refrigeration Controls s s s sas cc eea cea cs earo uat 22 ii 7 3 7 4 8 General Operation ss eave we Rw KC Y ROCA Se 27 8 1 8 2 8 3 8 4 8 5 8 6 8 7 Bath Fluid zu uu acl 27 8 1 1 Temperature Range a goes acm omm SEAN GS 27 8 1 2 MISGOSILY s buo Bah Rose Baw 27 8 1 3 Specife Heat e ses csee P Ed Red 5p er d 27 8 1 4 Thermal Conductivity 2 cup deer rep XO x m ca 28 8 1 5 Thermal Expansion sh s s soy oca UR ep ARR 28 8 1 6 Electrical Resistivity ss socso 28 8 1 7 Fl id Lifetime 525 ee own eR Gwe ea wae eem Bue BS ca 28 8 1 8 Mea as dba 28 8 1 9 al LETT 29 8 1 10 Commonly Used
35. S 232 Cable Wiring for IBM PC and Compatibles Instrument Computer DTE Connector Connector DB 9 Pin DB 9 Pin 1NC e 1DCD 1 o 1 3TxD rs 8 TxD 4NC 4 DTR 5GND 5GND 6NC 6 DSR 7 8CTS 8075 9NC 9NC Instrument Computer DTE Connector Connector DB 9 Pin DB 25 Pin 1NC e 2 RxD e 2TxD 3TxD 3RxD 4NC o m ARTS 5 w OK E 5 CTS 6NC 6 DSR 7RTS 8CTS t 8 DCD 9NC 20 DTR Figure 9 Serial Cable Wiring repeatedly until the serial interface menu is indicated with 5E 1R Finally press SET to enter the serial parameter menu In the serial interface parame ters menu are the BAUD rate the sample rate the duplex mode and the line feed parameter 10 1 2 1 BAUD Rate 52 The BAUD rate is the first parameter in the menu The display prompts with the BAUD rate parameter by showing B AU d Press SET to choose to set the BAUD rate The current BAUD rate value is displayed The BAUD rate of the bath s serial communications may be programmed to 300 600 1200 or 2400 BAUD BAUD rate is pre programmed to 1200 BAUD Use UP or DOWN to change the BAUD rate value Press SET to set the BAUD rate to the new value or EXIT to abort the operation and skip to the next parameter in the menu 10 Digital Communication Interface IEEE 488 Communication optional 10 1 2 2 10 1 2 3 10 1 2 4 10 1 3 10 2 10 2 1 Sample Period The sample period is
36. SET EXIT 9 Controller Operation Temperature Set point 9 3 9 3 1 Cut out reset function Press SET once more to reset the cut out SET Reset cut out This action also switches the display to the set temperature function To return to displaying the temperature press the EXIT button If the cut out is still in the over temperature fault condition the display continues to flash cut out The bath temperature must drop a few degrees below the cut out set point be fore the cut out can be reset Temperature Set point The bath temperature can be set to any value within the range and with resolu tion as given in the specifications The temperature range of the particular fluid used in the bath must be known by the operator and the bath should only be op erated well below the upper temperature limit of the liquid In addition the cut out temperature should also be set below the upper limit of the fluid Setting the bath temperature involves three steps 1 select the set point mem ory 2 adjust the set point value and 3 adjust the vernier if desired Programmable Set points The controller stores 8 set point temperatures in memory The set points can be quickly recalled to conveniently set the bath to a previously programmed tem perature set point To set the bath temperature one must first select the set point memory This function is accessed from the temperature display function by pr
37. and actions that may pose hazards to the user CAUTION identifies conditions and actions that may damage the in strument being used 1 2 1 A WARNINGS To avoid personal injury follow these guidelines GENERAL DO NOT use the instrument for any application other than calibration work The instrument was designed for temperature calibration Any other use of the instrument may cause unknown hazards to the user DO NOT use the instrument in environments other than those listed in the user s guide DO NOT overfill the bath Overflowing extremely cold or hot fluid may be harmful to the operator See Section 5 3 Bath Preparation and Filling for specific instructions Follow all safety guidelines listed in the user s manual Calibration Equipment should only be used by Trained Personnel If this equipment is used in a manner not specified by the manufacturer the protection provided by the equipment may be impaired Before initial use or after transport or after storage in humid or semi hu mid environments or anytime the instrument has not been energized for more than 10 days the instrument needs to be energized for a dry out 1 Before You Start Safety Information period of 2 hours before it can be assumed to meet all of the safety re quirements of the IEC 1010 1 If the product is wet or has been in a wet environment take necessary measures to remove moisture prior to apply ing power such as storage in a lo
38. ause of its very low cost availability and excellent tem perature control characteristics Water has very low viscosity and good thermal conductivity and heat capacity which makes it among the best fluids for control stability at lower temperatures Temperature stability is much poorer at higher temperatures because water condenses on the lid cools and drips into the bath Water is safe and relatively inert The electrical conductivity of water may pre vent its use in some applications Water has a limited temperature range from a few degrees above 0 C to a few degrees below 100 C At higher temperatures evaporation becomes significant Water used in the bath should be distilled or deionized to prevent mineral deposits Consider using an algicide chemical in the water to prevent contamination Ethylene Glycol The temperature range of water may be extended by using a solution of 50 water and 50 ethylene glycol antifreeze The characteristics of the ethylene glycol water solution are similar to water but with higher viscosity Use caution with ethylene glycol since the fluid is very toxic Ethylene glycol must be dis posed of properly Methanol Methanol is a relatively inexpensive fluid with a low temperature range Pure methanol has a temperature range from its freezing point of about 96 C to near its flash point at 54 C Vaporization is significant above 25 C so its use above this temperature is not recommended Methanol at low
39. ck the bath stability with the thermometer When both the bath and the thermometer have stabilized measure the bath tem perature with the thermometer and compute the temperature error erry which is the actual bath temperature minus the set point temperature For example if the bath is set for a lower set point of t 0 and the bath reaches a measured temperature of 0 3 C then the error is 0 3 C Next set the bath for the upper set point ty and after stabilizing measure the bath temperature and compute the error erry For example suppose the bath was set for 100 C and the thermometer measured 100 1 C giving an error of 0 1 Computing RO ALPHA Before computing the new values for Rg and ALPHA the current values must be known The values may be found by either accessing the probe calibration menu from the controller panel or by inquiring through the digital interface 59 7080 7081 Calibration Bath User s Guide 60 11 4 The user should keep a record of these values in case they may need to be re stored the future The new values Ry and ALPHA are computed by enter ing the old values for Ry and ALPHA the calibration temperature set points t and ty and the temperature errors err and err into the following equations ty 1 RO 1 0 l ALPHA 1 Jerr ALPHA 1 erry A ALPHA ALPHA ty For example Ry and ALPHA were previously set for 100 000
40. correct fluid for the temperature range of the calibration Bath fluids should be selected to operate safely with adequate thermal proper ties to meet the application requirements Also be aware that some fluids ex pand and could overflow the bath if not watched Refer to General Operation section 8 for information specific to fluid selection and to the MSDS sheet spe cific to the fluid selected Generally baths are set to one temperature and used to calibrate probes only at that single temperature This means that the type of bath fluid does not have to change Additionally the bath can be left energized reducing the stress on the system The bath generates extreme temperatures Precautions must be taken to prevent personal injury or damage to objects Probes may be extremely hot or cold when removed from the bath Cautiously handle probes to prevent personal in jury Carefully place probes on a heat cold resistant surface or rack until they are at room temperature It is advisable to wipe the probe with a clean soft cloth or paper towel before inserting it into another bath This prevents the mixing of fluids from one bath to another If the probe has been calibrated in liquid salt carefully wash the probe in warm water and dry completely before transferring it to another fluid Always be sure that the probe is completely dry before in serting it into a hot fluid Some of the high temperature fluids react violently to water or other liquid me
41. d electrician DO NOT use an extension cord or adapter plug e DO use a ground fault interrupt device This instrument contains a fluid A ground fault device is advised in case fluid is present in the electrical system and could cause an electrical shock e Always replace the power cord with an approved cord of the correct rat ing and type If you have questions contact a Hart Scientific Authorized Service Center see Section 1 3 e High voltage is used in the operation of this equipment Severe injury or death may result if personnel fail to observe the safety precautions Before working inside the equipment turn off the power and disconnect the power cord 7080 7081 Calibration Bath User s Guide BATH FLUIDS Fluids used in this bath may produce noxious or toxic fumes under certain circumstances Consult the fluid manufacturer s MSDS Material Safety Data Sheet Proper ventilation and safety precautions must be observed The instrument is equipped with a soft cutout user settable firmware and a hard cutout set at the factory Check the flash point boiling point or other fluid characteristic applicable to the circumstances of the bath oper ation Ensure that the soft cutout is adjusted to the fluid characteristics of the application As a guideline the soft cutout should be set 10 C to 15 C below the flash point of the bath fluid See Section 8 1 Heat Transfer Fluid for specific information on bath fluids and Section
42. de noted by may be entered in decimal or exponential notation Characters are shown in lower case although upper case may be used Spaces may be added within command strings and are simply ignored Backspace BS ASCII 8 may be used to erase the previous character A terminating CR is implied with all commands Power Control Functions The digital interface is capable of controlling the heating and cooling functions so that the bath can be remotely operated at any temperature within the range of the bath To allow the interface to control the heating and the cooling the front panel controls are disabled by 1 switching the heater switch to LOW 2 switching the cooling switch to OFF switching the cooling power switch to 10 Digital Communication Interface Power Control Functions Table 5 Interface Command Summary Command Command Returned Acceptable Command Description Format Example Returned Example Values Display Temperature Read current set point S etpoint set 9999 99 C or F Set current set point to n Ss etpoint n Instrument Range Read vernier v ernier Set vernier to n v ernier n Depends on Configuration Read temperature t emperature t 9999 99 C or F N Read temperature units f Set temperature units u nits c f Set temperature units to Celsius Set temperature units to Fahrenheit f Secondary
43. displaying the bath temperature Set the new units and resume temperature display Secondary Menu Functions which are used less often are accessed within the secondary menu The secondary menu is accessed by pressing SET and EXIT simulta neously and then releasing The first function in the secondary menu is the heater power display See Figure 7 on page 38 Heater Power The temperature controller controls the temperature of the bath by pulsing the heater on and off The total power being applied to the heater is determined by the duty cycle or the ratio of heater on time to the pulse cycle time This value may be estimated by watching the red green control indicator light or read di rectly from the digital display By knowing the amount of heating the user can tell if the bath is heating up to the set point cooling down or controlling at a constant temperature Monitoring the percent heater power will let the user know how stable the bath temperature is With good control stability the per cent heating power should not fluctuate more than 1 within one minute The heater power display is accessed in the secondary menu Press SET and EXIT simultaneously and release The heater power will be displayed as a percentage of full power Access heater power secondary menu ig Pct Heater power in percent To exit out of the secondary menu press EXIT To continue on to the propor tional band setting function pr
44. diums Be aware that cleaning the probe can be danger ous if the probe has not cooled to room temperature For optimum accuracy and stability allow the bath adequate stabilization time after reaching the set point temperature Comparison Calibration Comparison calibration involves testing a probe unit under test UUT against a reference probe After inserting the probes to be calibrated into the bath al low sufficient time for the probes to settle and the temperature of the bath to stabilize One of the significant dividends of using a bath rather than a dry well to cali brate multiple probes is that the probes do not need to be identical in construc tion The fluid in the bath allows different types of probes to be calibrated at the same time However stem effect from different types of probes is not to tally eliminated Even though all baths have horizontal and vertical gradients 19 7080 7081 Calibration Bath User s Guide 20 6 3 these gradients are minimized inside the bath work area see Section 7 4 Nev ertheless probes should be inserted to the same depth in the bath liquid Be sure that all probes are inserted deep enough to prevent stem effect From re search at Hart Scientific we suggest a general rule of thumb for immersion depth to reduce the stem effect to a minimum 15 x the diameter of the the sensor length Do not submerge the probe handles If the probe handles get too warm during calibratio
45. e bath Refer to the Specifications section for power details Refer to and read the cautions at the front of the manual concerning the brownout and over voltage protection Check the back panel label for the cor rect voltage and frequency prior to energizing the unit The bath power wires are located at the junction box at the back of the bath The wires are left undressed to accommodate a variety of connection schemes An electrician should be consulted for installation Use only wires and a circuit which are capable of supplying the maximum 13 amperes of current The wires must be fastened securely and insulated well 5 Installation Power Plug the stirring motor power cord into the stirrer socket at the back of the bath Set the heater switch on the front panel to the LOW position Set the cooling switch on the front panel to the OFF position and turn the bath on using the power switch on the front panel The baths turns on and begins to heat or cool to reach the previously programmed temperature set point The front panel LED display indicates the actual bath temperature 17 6 Bath Use General 6 6 1 6 2 Bath Use A CAUTION Read before placing the bath in service The information in this section is for general information only It is not de signed to be the basis for calibration laboratory procedures Each laboratory will need to write their own specific procedures General Be sure to select the
46. e to settle and stabilize There may be a small overshoot or undershoot of about 0 5 C 9 Controller Operation Bath Temperature 9 1 9 2 Controller Operation This section discusses in detail how to operate the bath temperature controller using the front control panel Using the front panel key switches and LED dis play the user may monitor the bath temperature set the temperature set point in degrees C or F monitor the heater output power adjust the controller propor tional band set the cut out set point and program the probe calibration param eters operating parameters serial and IEEE 488 interface configuration and controller calibration parameters Operation is summarized in Figure 7 Bath Temperature The digital LED display on the front panel allows direct viewing of the actual bath temperature This temperature value is what is normally shown on the dis play The units C or F of the temperature value are displayed at the right For example Bath temperature in degrees Celsius The temperature display function may be accessed from any other function by pressing the EXIT button Reset Cut out If the over temperature cut out has been triggered the temperature display al ternately flashes cut out i Indicates cut out condition The message continues to flash until the temperature is reduced and the cut out is reset The cut out has two modes automatic reset and manual reset The mode de term
47. e viscosity changes significantly with temperature and thermal expansion also occurs These oils have very high electrical resistivity Silicone oils are fairly safe and non toxic These oils are relatively expensive Fluid Characteristics Charts Table 3 and Figure 6 on pages 32 and 33 have been created to provide help selecting a heat exchange fluid media for your constant temperature bath The charts provide both a visual and numerical representation of most of the physi 8 General Operation Bath Fluid 8 1 11 1 8 1 11 2 cal qualities important in making a selection The list is not all inclusive many useable fluids may not have been shown in this listing Limitations and Disclaimer Every effort has gone into making these charts accurate however the data here does not imply any guarantee of fitness of use for a particular application Working near the limits of a property such as the flash point or viscosity limit can compromise safety or performance Sources of information sometimes vary for particular properties Your company s safety policies as well as personal judgement regarding flash points toxicity etc must also be considered You are responsible for reading the MSDS sheets and making a judgement here Cost may require some compromises as well Hart Scientific cannot be liable for the suitability of application or for any personal injury damage to equip ment product or facilities in using these fluids The c
48. e width modulator circuit which controls the amount of power applied to the bath heater The bath is operable within the temperature range given in the specifications For protection against solid state relay failure or other circuit failure the 35 7080 7081 Calibration Bath User s Guide 36 microcontroller automatically turns off the heater with a second mechanical re lay anytime the bath temperature is more than a certain amount above the set point temperature As a second protection device the controller is also equipped with a separate thermocouple temperature monitoring circuit which will shut off the heater if the temperature exceeds the cut out set point The controller allows the operator to set the bath temperature with higcalibration parameters The controller may be operated in temperature units of degrees Celsius or Fahrenheit The controller is operated and programmed from the front control panel using the four key switches and digital LED dis play The controller may also be optionally equipped with an RS 232 serial or IEEE 488 GPIB digital interface for remote operation Operation of the con troller using the front control panel is discussed following in Section9 Opera tion using the digital interfaces is discussed in Section10 When the controller is set to a new set point the bath will heat or cool to the new temperature Once the new temperature is reached the bath usually takes 10 15 minutes for the temperatur
49. es not turn on and the display re mains blank If a fault condition exists upon application of power the bath will not energize The bath needs to be plugged in to the line voltage for at least 10 minutes be fore turning power on This is only necessary for the first time that the bath is energized or when it is moved from one location to another If a high or low voltage condition exists for longer than 5 seconds the compres sor is de energized and the Mains Out of Range light on the back panel illumi nates indicating a fault condition Re energization is automatic upon correction of the fault condition and after a delay cycle of about 10 minutes High and low voltage protection limits at 230 VAC Voltage Cut out 12 5 203 257 VAC Voltage Cut in 7 5 213 247 VAC See the Caution in the front of this manual for additional information The heater indicator LED stays red but the temper ature does not increase If the display does not show cut out and shows the correct bath temperature consider the following possibilities Insufficient heating Insufficient heating may be caused by the heater power setting being too low especially at higher operating temperatures Switching to the higher heater power switch setting if available may solve the problem No heating This is caused by blown heater fuses and or burned out heaters Check the heater fuses to make sure that they are still good Access the heate
50. ess SET Return to temperature display Proportional Band In a proportional controller such as this the heater output power is proportional to the bath temperature over a limited range of temperatures around the setpoint This range of temperature is called the proportional band At the bot 9 Controller Operation Proportional Band tom of the proportional band the heater output is 100 At the top of the pro portional band the heater output is 0 Thus as the bath temperature rises the heater power is reduced which consequently tends to lower the temperature back down In this way the temperature is maintained at a fairly constant temperature The temperature stability of the bath depends on the width of the proportional band See Figure 8 on page 43 If the band is too wide the bath temperature will deviate excessively from the set point due to varying external conditions This is because the power output changes very little with temperature and the con troller cannot respond very well to changing conditions or noise in the system If the proportional band is too narrow the bath temperature may swing back and forth because the controller overreacts to temperature variations For best control stability the proportional band must be set for the optimum width an Proportional Band too Narrow Proportional Band too Wide Optimum Proportional Band Figure 8 Bath Temperature Fluctuation at Various Proportional Band Se
51. essing SET The number of the set point memory currently being used is shown at the left on the display followed by the current set point value 25 00 Bath temperature in degrees Celsius 39 7080 7081 Calibration Bath User s Guide 40 9 3 2 9 3 3 Press SET to accept the new selection and access the set point value Accept selected set point memory Set point Value The set point value may be adjusted after selecting the set point memory and pressing SET The set point value is displayed with the units C or F at the left 40 08 Set point 4 value in C If the set point value needs to be changed press UP or DOWN to adjust the set point value Increment display 42 50 New set point value When the desired set point value is reached press SET to accept the new value and access the set point vernier If EXIT is pressed instead then any changes made to the set point will be ignored SET Accept new set point value Set point Vernier The set point value can be set with a resolution of 0 01 C The user may want to adjust the set point slightly to achieve a more precise bath temperature The set point vernier allows one to adjust the temperature below or above the set point by a small amount with very high resolution Each of the 8 stored set points has an associated vernier setting The vernier is accessed from the set point by pressing SET The vernier setting is displayed as
52. harts include information on a variety of fluids which are often used as heat transfer fluid in baths Because of the temperature range some fluids may not apply to your bath About the Graph The fluid graph visually illustrates some of the important qualities of the fluids shown Temperature Range The temperature scale is shown in degrees Celsius A sense of the fluid s general range of application is indicated Qualities including pour point freeze point important viscosity points flash point boiling point and others may be shown Freezing Point The freezing point of a fluid is an obvious limitation to stir ring the freezing point is approached high viscosity may also limit good stirring Pour Point This represents a handling limit for the fluid Viscosity Points shown are at 50 and 10 centistokes Greater than 50 centi stokes stirring is very poor and unsatisfactory for bath applications At 10 centistokes and below optimum stirring can occur These are rules of thumb which have been useful for most applications Fume Point This is the point at which a fume hood should be used This point is very subjective in nature and is impacted by individual tolerance to different fumes and smells how well the bath is covered the surface area of the fluid in the bath the size and ventilation of the facility where the bath is located and others We assume the bath is well covered at this point This is also subject to company po
53. he bath set point The thermometer used must be able to measure the bath fluid temper ature with higher accuracy than the desired accuracy of the bath By using a good thermometer and carefully following procedure the bath can be calibrated to an accuracy of better than 0 02 C over a range of 100 degrees Calibration Points In calibrating the bath RO and ALPHA are adjusted to minimize the set point error at each of two different bath temperatures Any two reasonably separated bath temperatures may be used for the calibration However best results are ob tained when using bath temperatures which are just within the most useful op erating range of the bath The further apart the calibration temperatures the larger the calibrated temperature range but the calibration error is also greater over the range For instance if 0 and 100 C are chosen as the calibration temperatures the bath may achieve an accuracy of maybe 0 03 C over the range 10 to 110 C Choosing 30 C 70 C may allow the bath to a better accuracy of maybe 0 01 C over the range 25 to 75 C but outside that range the accuracy may be only 0 05 C Measuring the Set point Error The first step in the calibration procedure is to measure the temperature errors including sign at the two calibration temperatures First set the bath to the lower setpoint t Wait for the bath to reach the set point and allow 15 minutes to stabilize at that temperature Che
54. ines how the cut out is reset which allows the bath to heat up again When in automatic mode the cut out resets itself as soon as the temperature is low ered below the cut out set point With manual reset mode the cut out must be reset by the operator after the temperature falls below the set point When the cut out is active and the cut out mode is set to manual reset the display flashes c ut o ut until the user resets the cut out To access the reset cut out function press the SET button Access cut out reset function The display indicates the reset function 37 Display Temperature Secondary Functions Select Setpoint SET Y EXIT Adjust Setpoint I SET Y EXIT Adjust Vernier I SET Y EXIT Set Scale C F 1 SET SET EXIT v EXIT Display Power I SET Y EXIT Set Proportional Band SET Y EXIT EXIT Set Cutout Temp I SET SET Configuration Menu EX
55. ing the bath Bath Environment The Model 7080 7081 Bath is a precision instrument which should be located in an appropriate environment The location should be free of drafts extreme temperatures and temperature changes dirt etc The surface where the bath is placed must be level If used at higher temperatures where fluid vaporization is significant a fame hood should be used Allow sufficient air circulation by leaving at least six inches of space between the bath and nearby objects Provide overhead clearance to allow for safe and easy insertion and removal of probes for calibration DO NOT place under a cabinet or other structure Allow for overhead clearance Dry out Period Before initial use after transport and any time the instrument has not been en ergized for more than 10 days the bath will need to be energized for a dry out period of 1 2 hours before it can be assumed to meet all of the safety requirements of the IEC 1010 1 Bath Preparation and Filling The Model 7080 7081 Bath is not provided with a fluid Various fluids are available from Hart Scientific and other sources Depending on the desired tem perature range any of the following fluids as well as others may be used in the bath 15 7080 7081 Calibration Bath User s Guide 5 4 5 5 e Water Ethylene Glycol Water e Methanol e Halocarbon 0 8 e Mineral oil e Silicone oil Fluids are discussed in detail in Section 8 1 Remove
56. ition Command F4 controls the cooling power Setting the F parameter to 0 switches cooling to high power and 1 switches to low power Table 6 summarizes the serial control functions for heating and cooling Table 7 shows the recommended control settings for each operating temperature range The ranges may need to be adjusted depending on the bath and its particular use Table 6 Serial Power Control Functions Function Command 0 1 Heater F1 low high Refrigeration F2 off on Exp Valve 1 F3 off on Cooling Power F4 high low Exp Valve 2 F5 off on 57 7080 7081 Calibration Bath User s Guide Table 7 Temperature Range Control Functions Bath Temperature Cooling Expansion Expansion Pressure Setting Range C Heating Cooling Power Valve 1 Valve 2 Front Panel 80 to 40 low on high off off 3 psi Front Panel 40 to 15 low on low on off 50 psi Valve 1 Internal 20 to 40 low on low off on 80 psi Valve 2 Internal 40 to 110 low off N A N A N A N A iReadjust to minimum desired temperature for manual operation 58 11 Calibration Procedure Calibration Points 11 11 1 11 2 11 3 Calibration Procedure In some instances the user may want to calibrate the bath to improve the tem perature set point accuracy Calibration is done by adjusting the controller probe calibration constants RO and ALPHA so that the temperature of the bath as measured with a standard thermometer agrees more closely with t
57. licy Flash Point Point at which ignition may occur See flash point discussion in Section The point shown may be either the open or closed cup flash point See Figure 6 on page 33 31 7080 7081 Calibration Bath User s Guide Table 3 Table of Bath Fluids Fluid Lower Upper Thermal Thermal PartNo Temperature Temperature Flash Viscosity Specific Specific Heat Conductivity Expansion Resistivity Limit Limit Point centistokes Gravity cal g C cal s cm C cm cm C 1 070 Halocarbon 0 8 100 C v 70 NONE 5 7 50 C 1 71 40 C 0 2 0 0004 0 0011 5019 0 8 40 C 0 5 70 C Methanol 96 C fr 10 C fl cc 12 C 1 3 35 C 0 810 0 C 0 6 0 0005 20 C 0 0014 25 C 0 66 0 C 0 792 20 C 0 45 20 C Water 0 C fr 95 C b NONE 1 25 C 1 00 1 00 0 0014 0 0002 25 C 0 4 75 C Ethylene 30 C fr 90 C b NONE 7 0 C 1 05 0 8 0 C 0 001 Glycol 50 5020 2 50 C 0 7 100 C Mineral Oil No 7 10 C v 166 C fl 168 C 15 75 C 0 87 25 C 0 48 25 C 0 00025 25 C 0 0007 50 C 5 25 C 5011 5 125 C 0 84 75 C 0 53 75 C 0 81 125 C 0 57 125 C Silicone Oil Type 40 C v 130 C fl 133 C 5 25 C 0 92 25 C 0 4 0 00028 25 C 0 00105 1000 25 C 200 05 5010 10 150 C Silicone Oil Type 30 C v 209 C fl 211 C 10 25 C 0 934 25 C 0 43 40 0 00032
58. mmand Description Format Example Returned Example Values Read BO calibration parameter N Set BO calibration parameter to n Read BG calibration parameter Set BG calibration parameter to n Read low set point limit value tllow tl 999 tl 80 Set low set point limit to n tllow n tl 80 f f Read high set point limit value th igh f Set high set point limit to n th igh n b Miscellaneous not on menus Read firmware version number ver sion Read structure of all commands h elp list of commands 1 1 1 9 Set Heater f1 1 0 Oori Set heater to low 1 1 0 Set heater to high 1 1 1 Read Refrigeration 2 2 f2 9 f2 0 Set Refrigeration f2 1 0 v 0 1 Set Refrigeration to on 2 n 2 1 Set Refrigeration to off 2 n 2 0 Read Expansion Valve 1 3 3 f3 9 3 1 Set Expansion Valve 1 3 1 0 0 1 Set Expansion Valve 1 3 n 3 1 Set Expansion Valve 1 to off 3 n 3 0 Read Cooling Power N Set Cooling Power 4 1 0 0 1 Set Cooling Power to on n Set Cooling Power to off n Read Expansion Valve 2 5 15 15 9 15 1 Set Expansion Valve 2 5 1 0 0 1 Set Expansion Valve 2 to 5 n fal f f Set Expansion Valve 2 to off 5 n f5 0 f Legend Optional Command data 56 HIGH and adjusting the cooling temperature pressure to 5 psi Otherwise the interface would not be able to switch these functions off The 7080 7081 bath has five control functions with the digital interface These are 1 heater power high low 2 cooling on off 3 e
59. mometer and control probe are both fully inserted into the bath to minimize temperature gradi ent errors Bad control probe Check that the control probe has not been struck bent or damaged Refer to the previous solution for how to check the probe s resistance The controller shows that it is controlling at the proper temperature but the bath temperature is unstable If the bath does not achieve the expected degree of temperature stability when measured using a thermometer consider the following Wrong proportional band setting If the proportional band is set too narrow the bath will oscillate causing poor stability In this case increase the width of the proportional band If the proportional band setting is too wide the long term stability of the bath is affected In this case decrease the width of the band Refer to section 9 7 Bath fluid is too thick Make sure that the bath fluid used is less than 50 centi Stokes 10 is ideal at the temperature at which the bath is controlling Check the fluid manufacturer s specifications You should also change the bath fluid regularly and if it changes colors or be comes too thick Bad control probe Check that the control probe has not been struck bent or damaged Refer to the previous solution for how to check the probe s resistance The controller alternately heats for a while then cools Wrong proportional band setting If the proportional band is set too narro
60. n at high temperatures a heat shield could be used just below the probe handle This heat shield could be as simple as alumi num foil slid over the probe before inserting it in the bath or as complicated as a specially designed reflective metal apparatus When calibrating over a wide temperature range better results can generally be achieved by starting at the highest temperature and progressing down to the lowest temperature Probes can be held in place in the bath by using probe clamps or drilling holes in the access cover Other fixtures to hold the probes can be designed The ob ject is to keep the reference probe and the probe s to be calibrated as closely grouped as possible in the working area of the bath Bath stability is maximized when the bath working area is kept covered In preparing to use the bath for calibration start by e Placing the reference probe in the bath working area Placing the probe to be calibrated the UUT in the bath working area as close as feasibly possible to the reference probe Calibration of Multiple Probes Fully loading the bath with probes increases the time required for the tempera ture to stabilize after inserting the probes Using the reference probe as the guide be sure that the temperature has stabilized before starting the calibration 7 Parts Controls Front Panel 7 Parts and Controls 7 1 Front Panel The following controls and indicators are present on the controlle
61. o quickly heat the bath fluid up to the desired operating temperature The HIGH heater power setting may also be required for control at high tempera tures The LOW setting is used for control at lower temperatures and for scanning at slower rates When controlling at the HIGH heater power setting instead of LOW the proportional band may need to be increased typically by a factor of four to compensate for the increase in power gain Otherwise the temperature may oscillate 8 General Operation Cooling 8 6 8 7 The heater current is regulated by two 10 A fuses These protect against excess current due to short or failure The fuses are internal Contact an Authorized Service Center for assistance Cooling The Model 7080 7081 refrigeration system is a 2 stage cascade system This means there are two individual refrigeration systems or stages The first stage cools down or provides cooling for the second stage The second stage cools the bath This type of system is required to attain very low temperatures The first stage is an air cooled unit using R 507 refrigerant The fins of the air cooled condenser must be kept clean Dirty condensers cause inefficiency and limit the life of the system The second stage is cooled by the first via the heat exchange of the cascade condenser The refrigerant is ethylene cp grade and propane cp grade The system is statically charged Contact the factory if recharging is required
62. obe may be checked with an ohmmeter to see if it is open or shorted The probe is a platinum 4 wire Din 43760 type The resistance should read 0 2 to 2 0 ohms between pins 1 and 2 on the probe connector and 0 2 to 2 0 ohms between pins 3 and 4 The resistance should read from 100 to 300 ohms be tween pins 1 and 4 depending on its current temperature Corrupt controller memory Initialize the memory by performing a Factory Re set Sequence described in a previous solution 13 Troubleshooting Troubleshooting Problem Causes and Solutions The controller controls or attempts to control at an inaccurate temperature If the controller appears to operate normally except that the bath s temperature does not agree with the temperature measured by the user s reference ther mometer to within the specified accuracy consider the following Erroneous parameters Check that the calibration parameters are all correct according to the Report of Calibration If not reprogram the constants If the controller does not keep the correct parameters the memory backup battery may be weak causing errors in data See Low Battery in a previous solution Poor uniformity There may be an actual difference between the bath s control probe and the reference thermometer due to excess gradients in the bath Check that the bath has an adequate amount of fluid in the tank and that the stirrer is operating properly Also check that the reference ther
63. of the fluid affects the control stability temperature unifor mity and temperature settling time Fluids with higher conductivity distribute heat more quickly and evenly improving bath performance Thermal Expansion Thermal expansion describes how the volume of the fluid changes with temper ature Thermal expansion of the fluid used must be considered since the in crease in fluid volume as the bath temperature increases may cause overflow Excessive thermal expansion may also be undesirable in applications where constant liquid level is important Oils typically have significant thermal expansion Electrical Resistivity Electrical resistivity describes how well the fluid insulates against the flow of electric current In some applications such as measuring the resistance of bare temperature sensors it may be important that little or no electrical leakage oc cur through the fluid In this case consider a fluid with very high electrical resistivity Fluid Lifetime Many fluids degrade over time because of vaporization water absorption gel ling or chemical breakdown Often the degradation becomes significant near the upper temperature limit of the fluid Safety When choosing a fluid always consider the safety issues associated Obviously where there are conditions of extreme hot or cold there can be danger to people and equipment Fluids may also be hazardous for other reasons Some fluids may be considered toxic Contact with e
64. oint These are pro grammed at the factory when the bath is calibrated Do not alter the value of these parameters If the user desires to calibrate the bath for improved accuracy then calibrate RO and ALPHA according to the procedure given in Section1 1 L These parameters set the upper and lower set point limits of bath DO NOT change the values of these parameters from the factory set values To do so may present danger of the bath exceeding its temperature range causing damage or fire 10 Digital Communication Interface Serial Communications 10 10 1 10 1 1 10 1 2 Digital Communication Interface If supplied with the option the 7080 7081 bath is capable of communicating with and being controlled by other equipment through the digital interface Two types of digital interface are available the RS 232 serial interface and the IEEE 488 GPIB interface With a digital interface the bath may be connected to a computer or other equipment This allows the user to set the bath temperature monitor the tem perature and access any of the other controller functions all using remote com munications equipment In addition the heater power setting and cooling capacity may be controlled using the interface To enable the heater to be switched to high using the interface the HEATER switch must be set to the LOW position The COOLING switch must be set to OFF and the COOL ING POWER switch set to HI
65. ones xb tt as 51 10 1 2 uon eoe peace A OR P Go go HR Se X 51 10415241 BAUDRE he oh che p eR aea dee ip UE Rd Ge Bes dp teo dedos 22 10 1 2 2 Sample Penod 42 xoxo CR ee aa 53 10 1 2 3 Dupla RR x pub E Errem I eke 53 10 1 2 4 Eanefeed eS 53 10 1 3 Serial Operation doe Oa bag e 53 10 2 IEEE 488 Communication 53 10 2 1 d word MP ee ek a a BG SE ees 53 10 2 1 1 IEEE 488 Interface Address 54 10 2 2 TEEE 488 Operation i us ae es OR EES eom eS 54 10 3 Interface Commands 54 10 4 Power Control Functions 54 10 4 1 Heater Control 4 2 dm o Geb x Sek RAS E rhe BS 57 10 4 2 Cooling Control s HS we E de e Lon 57 11 Calibration 59 11 1 CadbrationPoints ens 59 11 2 Measuring Set point 59 11 3 Computing RO 59 11 4 Calibration Example 60 12 Maintenance 63 12 4 Drainingthe 64 13 Troubleshooting 4 65 131
66. onnector on the back panel connects the control probe to the temperature controller 23 7080 7081 Calibration Bath User s Guide OF RANGE 230V AC 50 Hz 3000 Watts Fuse 15 A 250V T 230 VAC 50H Single 15 Amps BROWN HOT BLUE NEUTRAL GREEN YELLOW GROUND SYSTEM FUSES INTERNAL Figure 4 Back Panel 2 The stirrer power socket provides power for the stirring motor 3 The terminal box holds the wires for connecting the bath to AC power The bath requires 230 VAC 109 50 or 60 Hz 13 A 4 bath serial number is located at the lower right corner of the back panel The model number is also printed here 5 Ifthe bath is supplied with a serial RS 232 interface the interface cable is attached to the back of the bath at the connector labelled SERIAL 6 Ifthe bath is supplied with a GPIB IEEE 488 interface the interface ca ble is attached to the back of the bath at the connector labelled 24 7 Parts Controls 7 4 7 8 A drain valve is provided for ease of removing the fluid media from the bath It is advisable to use a container of adequate size to hold the full load of fluid Some oils are more easily drained at higher temperatures The mains out of range indicator illuminates when a high low voltage condition exists for 5 seconds indicating a fault condition Lid There are two different types of lids see Figure 5 The s
67. portional Band Fluid Table Heater Proportional Fluid Temperature Setting Band Stability Methanol 80 C Low 0 04 C 0 001 C Methanol 40 C Low 0 04 C 0 0008 C Water 0 0 C Low 0 04 C 0 0008 C Water 30 0 C Low 0 04 C 0 0004 C Water 60 0 C Low 0 04 C 0 001 C Eth Gly 50 35 0 C Low 0 05 C 0 0005 C Eth Gly 50 60 0 C Low 0 05 C 0 001 C Eth Gly 50 100 0 C High 0 4 C 0 007 C Oil 35 0 C Low 0 1 C 0 003 C Oil 60 0 C Low 0 2 C 0 002 C Oil 100 C Low 0 2 C 0 003 C The proportional band adjustment may be accessed within the secondary menu Press SET and EXIT to enter the secondary menu and show the heater power Then press SET to access the proportional band ev Access heater power in secondary menu iP Pct i Heater power in percent To accept the new setting and access the cut out set point press SET Press ing EXIT exits the secondary menu ignoring any changes just made to the proportional band value 9 Controller Operation Cut out 9 8 SET Accept the new proportional band setting Cut out As a protection against software or hardware fault shorted heater triac or user error the bath is equipped with an adjustable heater cut out device that shuts off power to the heater if the bath temperature exceeds a set value This protects the heater and bath materials from excessive temperatures and most impor tantly protects
68. pping foam and adjust the compressor s hardware for proper vibration absorption as illustrated below in Figure 2 Set Up Set up of the bath requires careful unpacking and placement of the bath filling the bath with fluid installing the probe and connecting power Consult Section 11 7080 7081 Calibration Bath User s Guide 4 4 TOP VIEW OF COMPRESSOR Adjust X CECO ON MN 7 HARDWARE ADJUSTED FOR SHIPPING Adjust BACK OF BATH 2 HARDWARE ADJUSTED FOR OPERATION Figure 2 Semi hermetic Compressor for detailed instructions for proper installation of the bath Be sure to place the bath in a safe clean and level location Fill the bath tank with an appropriate liquid For operation at moderate bath temperatures clean distilled water works well Carefully pour the fluid into the bath tank through the large rectangular access hole above the tank avoiding spilling any fluid The fluid must not exceed a height of 1 2 inch below the bath lid The control probe MUST BE inserted through the lid into the bath and plugged into the socket at the back of the bath DO NOT operate the bath without the control probe properly installed Power Plug the bath power cord into a mains outlet of the proper voltage frequency and current capability 230 VAC 410 60 Hz 15 A Set the HEATER switch on the front panel to position LOW and
69. r fuses by removing the L shaped panel covering the display electronics If they are blown and continue to blow when replaced the heaters may be shorted If you suspect that the heaters are shorted or burned out contact an Authorized Service Center for assistance Too much cooling Try reducing the cooling capacity by increasing the cooling pressure switching the cooling power switch to LOW or switching off the cooling altogether 65 7080 7081 Calibration Bath User s Guide 66 Problem Causes and Solutions The controller display flashes CUT OUT and the heater does not operate If the display flashes CUT OUT alternately with the correct process tempera ture check the following Wrong cut out setting The cut out disconnects power to the heaters when the bath temperature exceeds the cut out set point This causes the bath tempera ture to drop back down to a safe value If the cut out mode is set to AUTO the heater switches back on when the temperature drops If the mode is set to RE SET the heater only comes on again when the temperature is reduced and the cut out is manually reset by the operator Refer to section 9 8 Check that the cut out set point is adjusted to 10 or 20 C above the desired maximum bath operating temperature and that the cut out mode is set as desired Bad cut out If the cut out activates when the bath temperature is well below the cut out set point or the cu
70. r front panel see Figure 3 below 1 the digital LED display 2 the control buttons 3 the bath on off power switch 4 the control indicator light 5 the heater power switch and 6 the cooling power switch 1 The digital display is an important part of the temperature controller It displays the set point temperature and bath temperature as well as the various other bath functions settings and constants The display shows temperatures in values according to the selected scale units C or F 2 The control buttons SET DOWN UP and EXIT are used to set the bath temperature setpoint access and set other operating parameters and access and set bath calibration parameters A brief description of the functions of the buttons follows SET Used to display the next parameter menu and to set parameters to the displayed value DOWN Used to decrement the displayed value of settable parameters 7080 HIGH PRECISION BATH 80 C to 110 C Hart Scientific gz 9 HEATING COOLING TEMPERATURE COOLING POWER EVAPORATING TEMPERATURE er HIGH STAGE CASCADE REFRIGERATION Figure 3 Front Panel 21 7080 7081 Calibration Bath User s Guide 22 7 2 UP Used to increment the displayed value EXIT Used to exit from a menu When EXIT is pressed any changes made to the displayed value will be ignored 3 The on off switch controls power to the entire bath including the stirring motor
71. r to and read the cautions at the front of the manual concerning the brownout and over voltage protection Check the back panel label for the correct voltage and frequency prior to energizing the unit Power to the bath passes through a filter to prevent switching spikes from being transmitted to other equipment To turn on the bath switch the control panel power switch to the ON position The stirring motor turns on the LED display begins to show the bath tempera ture and the heater turns on or off until the bath temperature reaches the pro grammed set point When powered on the control panel display briefly shows a four digit number This number indicates the number of times power has been applied to the bath Also briefly displayed is data which indicates the controller hardware configu ration This data is used in some circumstances for diagnostic purposes Heater The power to the bath heater is precisely controlled by the temperature control ler to maintain a constant bath temperature Power is controlled by periodically switching the heater on for a certain amount of time using a solid state relay The front panel red green control indicator shows the state of the heater The control indicator glows red when the heater is on and glows green when the heater is off The indicator pulses constantly when the bath is maintaining a sta ble temperature The heater has two power level settings The HIGH heater power setting is used t
72. rate to the displayed value SA 80 i New sample period Duplex Mode The next parameter is the duplex mode The duplex mode may be set to full du plex or half duplex With full duplex any commands received by the bath via the serial interface are immediately echoed or transmitted back to the device of origin With half duplex the commands are executed but not echoed The du plex mode parameter is indicated by 9 Controller Operation IEEE 488 Parameters Menu 9 12 4 9 13 9 13 1 Serial duplex mode parameter Press SET to access the mode setting Linefeed The final parameter in the serial interface menu is the linefeed mode This pa rameter enables on or disables off transmission of a linefeed character LF ASCII 10 after transmission of any carriage return The linefeed parameter is indicated by IEEE 488 Parameters Menu Baths may optionally be fitted with an IEEE 488 GPIB interface In this case the user may set the interface address within the IEEE 488 parameter menu This menu does not appear on baths not fitted with the interface The menu is indicated by IEEE 488 parameters menu Press SET to enter the menu IEEE 488 Address The IEEE 488 interface must be configured to use the same address as the ex ternal communicating device The address is indicated by Addr ESS IEEE 488 interface address Press SET to access the address setting 49 7080 7081 Calib
73. ration Bath User s Guide 50 9 14 9 14 1 9 14 2 9 14 3 A Current 488 interface address Adjust the value with UP or DOWN and then use SET to set the address to the displayed value Add 15 i New IEEE 488 interface address Calibration Parameters The operator of the bath controller has access to a number of the bath calibra tion constants namely CTO BO BG H and L These values are set at the fac tory and must not be altered The correct values are important to the accuracy and proper and safe operation of the bath Access to these parameters is avail able to the user only so that in the event that the controller s memory fails the user may restore these values to the factory settings The user should have a list of these constants and their settings with the manual CAUTION DO NOT change the values of the bath calibration constants from the factory set values The correct setting of these parameters is im portant to the safety and proper operation of the bath The calibration parameters menu is indicated by Calibration parameters menu Press SET five times to enter the menu CTO Parameter CTO sets the limit of the over temperature cut out This is not ad justable by software but is adjusted with an internal potentiometer For the 7080 7081 baths this parameter should read between 110 and 130 BO and BG These parameters calibrate the accuracy of the bath set p
74. rming the memory check you need to record the controller maintain controller pa calibration parameters found in the CAL menu of the instrument and any rameters or parameters user adjusted parameters that you have changed such as the programmable are reset each time the set points and proportional band power to the unit is Memory Check removed Doing a memory check is the easiest way to verify the ability of the battery to maintain controller parameters 1 Power off the instrument 2 Disconnect the instrument from AC power for 10 seconds 3 Reconnect the AC power and power on the instrument 4 If the display shows InIT and or the cycle count shows a low number such as 0002 the battery is spent and should be replaced Contact an Authorized Ser vice Center for assistance 5 After replacing the battery you must reprogram the calibration and user ad justable parameters into the controller Comments EMC Directive Hart Scientific s equipment has been tested to meet the European Electromag netic Compatibility Directive EMCEMC Directive 89 336 EEC The Decla ration of Conformity for your instrument lists the specific standards to which the unit was tested The instrument was designed specifically as a test and measuring device Com pliance to the EMC directive is through IEC 61326 1 Electrical equipment for measurement control and laboratory use requirements 1998 As noted in the IEC 61326 1 the instrument can ha
75. rrer on the standard lid and the pump on the optional pump lid 5 The probe hole is for inserting the control probe into the bath 26 8 General Operation Bath Fluid 8 1 General Operation Bath Fluid Many fluids work with 7080 7081 bath Choosing a fluid requires consider ation of many important characteristics of the fluid Among these are tempera ture range viscosity specific heat thermal conductivity thermal expansion electrical conductivity fluid lifetime safety and cost Temperature Range One of the most important characteristics to consider is the temperature range of the fluid Few fluids work well throughout the complete temperature range of the bath The temperature at which the bath is operated must always be within the safe and useful temperature range of the fluid used The lower tem perature range of the fluid is determined by the freeze point of the fluid or the temperature at which the viscosity becomes too great The upper temperature is usually limited by vaporization flammability or chemical breakdown of the fluid Vaporization of the fluid at higher temperatures may affect temperature stability because of cool condensed fluid dripping into the bath from the lid The bath temperature should be limited by setting the safety cut out so that the bath temperature cannot exceed the safe operating temperature limit of the fluid Viscosity Viscosity is a measure of the thickness of a fluid how easil
76. s SET to program the address The default address is 22 Change the device address of the bath if necessary to match the address used by the communication equipment by pressing UP or DOWN and then SET IEEE 488 Operation Commands may now be sent via the IEEE 488 interface to read or set the tem perature or access other controller functions All commands are ASCII charac ter strings and are terminated with a carriage return CR ASCII 13 Interface commands are listed below Interface Commands The various commands for accessing the bath controller functions via the digi tal interfaces are listed in this section see Table 5 These commands are used with both the RS 232 serial interface and the IEEE 488 GPIB interface In ei ther case the commands are terminated with a carriage return character The in terface makes no distinction between upper and lower case letters hence either may be used Commands may be abbreviated to the minimum number of letters which determines a unique command A command may be used to either set a parameter or display a parameter depending on whether or not a value is sent with the command following a character For example s CR returns the current set point and s250 00 CR sets the set point to 50 00 degrees In Table 5 characters or data within brackets and are optional for the command A slash denotes alternate characters or data Numeric data
77. t out does not reset when the bath temperature drops and it is manually reset the cut out circuitry may be faulty Try performing the Factory Reset Sequence explained below Factory Reset Sequence Hold the SET and EXIT keys down at the same time while powering up the unit The display shows init the model number and the firmware version Each of the controller parameters and calibration con stants must be re programmed The values can be found on the Report of Cali bration that was shipped with the instrument The display flashes CUT OUT alternately with an incorrect process temperature Low battery A problem could exist with the memory back up battery If the bat tery voltage is insufficient to maintain the memory data may become scrambled causing problems A nearby large static discharge may also affect data in mem ory Access the battery by removing the L shaped panel covering the display electronics Corrupt controller memory If the problem reoccurs after the battery is re placed initialize the memory by performing a Factory Reset Sequence de scribed in a previous solution The controller displays the wrong temperature and the bath continually heats or cools regardless of the set point value Bad control probe The bath control probe may be disconnected burned out or shorted Check first that the probe is connected properly to the socket in the rear of the bath labeled PROBE The pr
78. t temperature Set the heater switch to position HIGH to allow the bath to more quickly reach a higher temperature The HIGH setting may be necessary to reach and control at higher temperatures When setting the set point temperature be careful not to exceed the temperature limit of the bath fluid The over temperature cut out should be correctly set for added safety See Section9 8 If operating the bath below 45 C set the COOLING power switch to ON The cooling temperature may require adjustment to provide the proper amount of cooling See Section8 6 To obtain optimum control stability adjust the proportional band as discussed in Section9 7 5 Installation Bath Environment 5 5 1 5 2 5 3 Installation A CAUTION Before placing the bath in service READ SECTION 6 ENTI TLED BATH USE This bath is not designed to be portable Therefore moving the bath once it has been installed should be kept to a minimum The fluid can splash causing injury or if the bath and cart tip the fluid could cause damage to the surrounding area and personal injury to personnel If the bath must be moved be sure to drain the fluid to prevent any injury The bath is not designed to be lifted The wheels allow it to be rolled If the unit must be lifted contact an Authorized Service Center WARNING Never move a bath that is full of fluid This action could be extremely dangerous and could result in personal injury to the person mov
79. tandard lid has a stir ring motor with rectangular access hole and the optional lid has a recirculation pump Their features are described with reference to figure numbers as follows 1 2 3 There are latches at the front and back of the lid which attach the lid se curely to the bath The latches allow quick and easy removal of the lid The small round hole in the lid labelled THERMOMETER LIQUID LEVEL is for filling or removing fluid checking the liquid level or for placing probes and devices into the bath Normally the hole is covered with the rubber plug Holes may be drilled in the rubber stopper for in serting probes into the bath The rectangular access hole in the standard lid may be used for filling and emptying the bath and inserting devices into the bath This rectangu lar access hole provides the normal working area of the bath The work ing area is defined as one inch from the access hole sides one inch from the access hole bottom and three inches from the top of the fluid Nor mally this hole should be covered to insulate the bath Covers may be purchased separately from Hart Scientific JO Standard Lid Optional Pump Lid Figure 5 Lid Options 25 7080 7081 Calibration Bath User s Guide On the optional pump lid the inlet and outlet pipes replace the rectangu lar access hole 4 The motor on the lid drives the sti
80. tempera ture at which the refrigerant is evaporating The cooling temperature reg ulating valve is used to adjust this pressure 10 The cascade refrigeration indicator lights show which cooling stages are operating The High Stage is on when the high stage refrigeration is operating The Low Stage light comes on when the refrigeration has been sufficiently cooled by the high stage compressor for the second or low stage compressor to be automatically engaged Both High and Low stages must be on for the bath to cool 7 Parts Controls Back Panel 7 3 Table 2 Temperature Chart Set the Cooling Temperature to this Refrigerant Cooling Power Desired Bath Temperature Pressure Switch Degrees C Degrees F PSIG Position 45 113 Off N A 35 95 90 MAX LOW 30 86 90 MAX LOW 25 77 90 LOW 15 59 90 MAX LOW 10 50 90 MAX LOW 5 41 90 MAX LOW 5 23 90 LOW 10 14 90 MAX LOW 15 5 80 LOW 25 13 68 LOW HIGH 30 22 62 LOW HIGH 35 31 56 LOW HIGH 45 49 43 HIGH 50 58 37 HIGH 55 67 30 HIGH 65 85 16 HIGH 70 94 10 HIGH 75 103 5 HIGH Back Panel The back panel has the following features see Figure 4 1 the probe connec tor 2 the stirrer power outlet 3 the terminal box for power connection 4 the serial number label 5 amp 6 optional serial and IEEE interface connectors and 7 the bath drain 1 The probe c
81. the bath fluids from being heated beyond the safe operating temperature preventing hazardous vaporization breakdown or ignition of the liquid The cut out temperature is programmable by the operator from the front panel of the controller It must always be set below the upper temperature limit of the fluid and no more than 10 degrees above the upper temperature limit of the bath If the cut out is activated because of excessive bath temperature power to the heater is shut off and the bath cools until it reaches a few degrees below the cut out set point temperature At this point the action of the cut out is deter mined by the setting of the cut out mode parameter The cut out has two selectable modes automatic reset or manual reset If the mode is set to auto matic then the cut out automatically resets itself when the bath temperature falls below the reset temperature allowing the bath to heat up again If the mode is set to manual the heater remains disabled until the user manually resets the cut out The cut out set point may be accessed within the secondary menu Press SET and EXIT to enter the secondary menu and show the heater power Then press SET twice to access the cut out set point Access heater power secondary menu SET Access cut out set point CG cioc Cut out set point To change the cut out set point press UP or DOWN 45 7080 7081 Calibration Bath User s Guide
82. the next parameter in the menu and prompted with 5A fi PLE The sample period is the time period in seconds between temperature measurements transmitted from the serial interface If the sample rate is set to 5 the bath transmits the current measurement over the serial interface approxi mately every five seconds The automatic sampling is disabled with a sample period of 0 Press SET to choose to set the sample period Adjust the period with UP or DOWN and then use SET to set the sample rate to the dis played value Duplex Mode The next parameter is the duplex mode indicated with d UPL The duplex mode may be set to half duplex HA LF or full duplex FULL With full duplex any commands received by the bath via the serial interface are immedi ately echoed or transmitted back to the device of origin With half duplex the commands are executed but not echoed The default setting is full duplex The mode may be changed using UP or DOWN and pressing SET Linefeed The final parameter in the serial interface menu is the linefeed mode This pa rameter enables 40 n or disables 8 F F transmission of a linefeed charac ter LF ASCII 10 after transmission of any carriage return The default setting is with linefeed on The mode may be changed using UP or DOWN and pressing SET Serial Operation Once the cable has been attached and the interface set up
83. ttings The optimum proportional band width depends on several factors among which are fluid volume fluid characteristics viscosity specific heat thermal conduc tivity heater power setting operating temperature and stirring Thus the pro portional band width may require adjustment for best bath stability when any of these conditions change Of these the most significant factors affecting the op timum proportional band width are heater power setting and fluid viscosity The proportional band should be wider when the higher power setting is used so that the change in output power per change in temperature remains the same The proportional band should also be wider when the fluid viscosity is higher because of the increased response time The proportional band width is easily adjusted from the bath front panel The width may be set to discrete values in degrees C or F depending on the selected units The optimum proportional band width setting may be determined by monitoring the stability with a high resolution thermometer or with the control ler percent output power display Narrow the proportional band width to the point at which the bath temperature begins to oscillate and then increase the 43 7080 7081 Calibration Bath User s Guide 44 band width from this point to 3 or 4 times wider Table 4 lists typical propor tional band settings for optimum performance with a variety of fluids at selected temperatures Table 4 Pro
84. ture limits Be sure that the probe handle temperature limit is not exceeded in the air above the instrument The instrument and any thermometer probes used with it are sensitive in struments that can be easily damaged Always handle these devices with care Do not allow them to be dropped struck stressed or overheated 1 Before You Start Authorized Service Centers 1 3 COLD BATHS Refrigerated baths require that the condensing coil be cleaned periodi cally Accumulation of dust and dirt on the condenser will result in pre mature failure of the compressor This bath has been equipped with a brownout and over voltage protection device as a safety feature to protect the system components Mode of Operation This bath needs to be plugged into the line voltage for at least 2 minutes before operation This is only necessary for the first time the bath is energized or when it is moved from one location to an other Turning the bath ON or OFF does not trigger the delay If a High Low voltage condition exists for longer than 5 seconds the bath de energizes An amber indicator on the back panel lights when this con dition exists Re energization is automatic upon correction of the fault condition and af ter a delay cycle of about 2 minutes If a fault condition exists upon appli cation of power the bath will not energize Under and Over Voltage Protection at 230 VAC Voltage Cutout 12 5 203 257 VAC Voltage Cut In
85. ve varying configurations The instrument was tested in a typical configuration with shielded RS 232 cables 13 Troubleshooting Comments 13 2 1 1 13 2 2 Emission Testing The instrument fulfills the limit requirements for Class A equipment but does not fulfill the limit requirements for Class B equipment The instrument was not designed to be used in domestic establishments Low Voltage Directive Safety In order to comply with the European Low Voltage Directive 73 23 EEC Hart Scientific equipment has been designed to meet the IEC 1010 1 EN 61010 1 and the IEC 1010 2 010 EN 61010 2 010 standards 69
86. w the bath will oscillate between too much heating and too much cooling causing instability Increase the width of the proportional band until the temperature sta bilizes Refer to section 9 7 67 7080 7081 Calibration Bath User s Guide 68 13 2 13 2 1 Problem Causes and Solutions The bath does not Too much heating Check that the control indicator glows green showing that achieve low temperatures the controller is attempting to cool The heaters may be disabled as a test by temporarily removing the heater fuses Check the refrigeration system by switching the heater to low switching the cooling on setting the cooling power to high setting the cooling pressure to ap proximately 7 PSI and setting the cooling temperature to 10 15 C below the bath set point The bath should then cool as quickly as possible to the new set point Insufficient cooling This may be caused by lack of refrigerant because of a leak in the system Power Up The unit is equipped with external operator accessible fuses If a fuse blows it may be due to a power surge or failure of a component Replace the fuse once DO NOT replace the fuse with one of a higher current rating Always replace the fuse with one of the same rating voltage and type If the fuse blows a second time it is likely caused by failure of a component part Contact an Authorized Service Center Section 1 3 for assistance The controller does not Note Before perfo
87. w humidity temperature chamber operat ing at 50 C for 4 hours or more Overhead clearance is required Do not place the instrument under a cabi net or other structure Always leave enough clearance to allow for safe and easy insertion and removal of probes e The instrument is intended for indoor use only e bath is a precision instrument Although it has been designed for op timum durability and trouble free operation it must be handled with care Position the bath before the tank is filled with fluid by rolling it into place DO NOT attempt to lift the bath DO NOT move a bath filled with fluid BURN HAZARD e Extremely cold temperatures may be present in this equipment Freezer burns and frostbite may result if personnel fail to observe safety precau tions e High temperatures may be present in this equipment Fires and severe burns may result if personnel fail to observe safety precautions ELECTRICAL HAZARD e These guidelines must be followed to ensure that the safety mechanisms in this instrument will operate properly This instrument must be plugged into a 230V AC electric outlet of the appropriate frequency The power cord of the instrument is equipped with a three pronged grounding plug for your protection against electrical shock hazards It must be plugged directly into a properly grounded three prong receptacle The receptacle must be installed in accordance with local codes and ordinances Consult a qualifie
88. xpansion valve open closed 4 cooling power high low and 5 expansion valve 2 open closed 10 Digital Communication Interface Power Control Functions 10 4 1 10 4 2 Heater Control To control the heater with the digital interface the front panel heater switch must be set to LOW 500 W The heater function is controlled with the F1 command Setting the F1 parameter to 0 sets the heater to LOW 500 W and setting it to 1 sets the heater to HIGH 1000 W Sending F1 with no value causes the controller to return the heater setting value When the heater setting is changed a pop is heard as the heater relay opens or closes Cooling Control To control the refrigeration power with the serial interface the front panel cool ing switch must be off The refrigeration power function is controlled with se rial F2 command Setting the F2 value to 0 turns the refrigeration off and setting it to 1 turns it on F2 alone returns 0 or 1 showing the state of the re frigeration power control The and 5 commands control the cooling temperature or expansion valves These valves adjust the cooling temperature which sets the cooling ca pacity Setting to 0 turns off valve 1 and 1 turns the valve on Setting F5 to 0 turns off valve 2 and 1 turns the valve on A command with no value re turns the current value To control the cooling power the COOLING POWER switch must be in the HIGH pos
89. y it can be poured and mixed Viscosity affects the temperature uniformity and stability of the bath With lower viscosity fluid mixing is better therefore creating a more uni form temperature throughout the bath This improves the bath response time which allows it to maintain a more constant temperature For good control the viscosity should be less than 10 centistokes 50 centistokes is about the practi cal upper limit of allowable viscosity Viscosities greater than this cause very poor control stability because of poor stirring and may also overheat or damage the stirring motor With oils viscosity may vary greatly with temperature When using fluids with higher viscosities the controller proportional band may need to be increased to compensate for the reduced response time Otherwise the temperature may begin to oscillate Specific Heat Specific heat is the measure of the heat storage ability of the fluid Specific heat though to a lesser degree also affects the control stability It also affects the heating and cooling rates Generally a lower specific heat means quicker heating and cooling Different specific heats may require an adjustment to the proportional band to compensate for the change in the sensitivity of the bath temperature to heat input 27 7080 7081 Calibration Bath User s Guide 28 8 1 4 Thermal Conductivity Thermal conductivity measures how easily heat flows through the fluid Ther mal conductivity
90. yes skin or inhalation of vapors may cause injury A proper fume hood must be used if hazardous or bothersome va pors are produced Fluids may be flammable and require special fire safety equipment and proce dures An important characteristic of the fluid to consider is the flash point The flash point is the temperature at which there is sufficient vapor given off so that when there is sufficient oxygen present and an ignition source is applied the va por will ignite This does not necessarily mean that fire will be sustained at the flash point The flash point may be either of the open cup or closed cup type Either condition may occur in a bath situation The closed cup temperature is always the lower of the two The closed cup represents the contained vapors in side the tank and the open cup represents the vapors escaping the tank Oxygen and an ignition source will be available inside the tank 8 General Operation Bath Fluid 8 1 10 8 1 10 1 8 1 10 2 8 1 10 3 Environmentally hazardous fluids require special disposal according to ble federal or local laws after use Cost Cost of bath fluids may vary greatly from cents per gallon for water to hun dreds of dollars per gallon for synthetic oils Cost may be an important consid eration when choosing a fluid Commonly Used Fluids Below is a description of some of the more commonly used fluids and their characteristics Water Water is often used bec

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