Neutron Monitor Digipig - KWD Nuclear Instruments
Contents
1. Testpoint discriminator Discriminator adjustment Figures 5 7 NEUTRON MONITOR 2222 A J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw C3 HV adjustment2. 2600 V DC to DC converter BF tube minator Memory 232 Detector Presentation board Display board Mem brane panel Signal Out Figure 5 6 NEUTRON MONITOR 2222 A Block diagram J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 A SERVICE MANUAL 21 2009 02 18 5 7 Typical plateau curve 1000 900 800 700 600 500 cps 400 300 0 t t 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 3100 High Voltage Figure 5 7 NEUTRON MONITOR 2222 A Typical plateau curve for the BF3 tube J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw 2222 SERVICE MANUAL 22 WEDHOLM MEDICAL AB 2009 02 18 5 8 Adjustment of sensitivity Q eel OM 1000 Response for 40 Coulombs 10 Coulombs 1 Figure 5 8 Amplifier check J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 A SERVICE MANUAL 2009 02 18 5 9 Presentation board HV testpoint HV on off HV switch 23 Amplifier adjustment Testpoint amplifier
3. 2 1 10 PC communication The communication is enabled when the switch SW1 3 is in position on 2 1 11 Trouble shooting PC communication Check that the switch SW1 3 is in position on Check the communication parameters Baud 9600 Start 1 Stopp 1 Data 8 Check communication port Check the cable between Digipig and the computer Pin 2 Pin2 Pin 3 Pin 3 Pin 5 Pin 5 2 1 12 Background lighting The light button can be pushed to light the display during 4 seconds This short time is set because this lighting consumes much power 2 1 13 Trouble shooting background lighting Check that the CPU sends a signal out on IC2 25 when the light button is pushed and that this signal returns after about 4 seconds This signal goes via T2 on the Display board to the DC AC transformer on the same board It shall transform the signal to an AC of about 80V 2 1 14 Summer The instrument is equipped with a summer which a o confirm every keyboard push Alarm when the dos rate is over the alarm level and when the dos rate is low see manual J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 7 2009 02 18 2 1 15 Trouble shooting summer The summer Is placed on the display board and tts signal comes from IC2 24 This signal varies during the time period the summer is to be heard This signal also passes T2 on the display board 2 1 16 HV setting A 5 voltage generated f
4. _ E Figure 5 1 NEUTRON MONITOR 2222 Detector unit J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 16 2009 02 18 5 2 Neutronsensitivity o Broad beam 0 90 se figure 5 3 Broad beam 0 0 se figure 5 3 Isotropic neutrons ni i sm Hmm i HIHI ms TM n inh Hm c simu gt ER BHI Rem response HILL il Hin ma Th r LI 10 HI HHI HHI THI TI m LLL LM TUA Neutron sensitivity cps per neutron cm sec Neutron energy eV Figure 5 2 NEUTRON MONITOR 2222 A Neutron sensitivity as a function of energy J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 A SERVICE MANUAL 17 2009 02 18 5 3 Angular dependence 240 120 255 105 270 90 285 75 30 22760 30 0 345 15 30 0 Figure 5 3 NEUTRON MONITOR 2222 A Angle dependence in relation to count speed J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw 2222 2009 02 18 WEDHOLM MEDICAL AB 5 4 Neutronsensitivity Se ae cm LEE Co E
5. AB 2222 SERVICE MANUAL 3 2009 02 18 a Nothing happens Does the voltage over M exceed 2 5 V This signal must be above 2 5 V to be able to operate the transistor T4 The signal M becomes the signal ON OFF at pushed button which then is voltage divided by R27 and R28 Check the voltage backward towards the batteries if M is not over 2 5 V According to the leaflet for IC15 the voltage in must be at least V to be able to give 5 V Check that there is 6 V on IC15 8 b The LCD blinks but drops off when ON OFF is released This indicates that there is voltage from the batteries and that IC15 and IC16 gets grounded shutdown so that they start but that the CPU does not take over Check if there is 5 V to the CPU for example 2 26 Check if IC2 29 is set high This is a must for the instrument to work after ON OFF has been released This port is set high in the beginning of the program and if it is not this indicates that the CPU does not reach the program code in IC4 Check that the PROM is correctly mounted Check that IC1 sends a reset pulse to the CPU on about 4 5 V immediately after it has received VCC It is unusual that a CPU fails 2 1 3 Instrument operation When the instrument is in operation the CPU communicates with its peripheral circuits which are IC4 PROM Contains the program code IC5 RAM Here the CPU stores the measurement values and measuring data it has presented and needs in the future IC10 Real ti
6. is hole mounted 2 1 6 Voltage alarm IC15 has a low bat function for alarm at low battery voltage via the voltage divider R30 and R31 which triggers IC15 at about 6 0 V battery voltage and grounds IC15 7 which is connected to the CPU pin 48 which in turn lits up the LO BATT segment on the LCD display 2 1 7 Data collection The accumulated number of pulses during 5 minutes is calculated to the average dose rate and stored in the instrument RAM memory together with date and time for measurement These data are stored in a FIFO memory which means that when 200 5 minute measurements are stored the next will write over the oldest In this memory also the total number of pulses is stored if integral mode is chosen at shut off 2 1 8 Memory print out Print out of up to 200 measurement values is done by pushing the PRT button This only results in a copy of the memory to the RS 232 port but does not erase of change the measurement values in any way A printout looks as follows 37 87 uSv h 970416 10 30 38 12 uSv h 970416 10 35 J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 6 2009 02 18 2 1 9 Trouble shooting printout If not printout takes place and the measurement has been going on for more than 5 minutes either the RAM is broken or the communication has failed Check that the CPU sends out a pulse train on IC2 21 and that this pulse train then is on 9V after IC6 14
7. on the presentation board are shown in Figure 5 8 for two different input charges The amplifier is very sensitive and to get the correct reading it is necessary to protect the amplifier from external electromagnetic fields 3 2 Discriminator check The discriminator level can be set by P2 drawing C 321 208 The nominal value is from 0 5V to 2V measured on R18 D5 R19 and R20 common point This level regulation is done to avoid that gamma pulses and noise are counted The final discrimination adjustment is done at the neutron calibration The pulse out is checked from the front panel of the instrument Normally the output amplitude is about 5V if the input pulse is 10 Coulombs Then input pulse of 1073 Coulombs will normally not give any pulse at the external output 3 3 Check of LCD deflection Feed negative pulses into the amplifier as described in Chapter 3 1 Check of LCD deflection and set the discriminator level to 1V Let the pulse frequency be 4 pulses per second pps The dose rate shall then be approximately 0 010 mSv h It depends on the calibration of the monitor Let the pulse frequency be 720 000 pps check that OVERFLOW is lit on the LCD Check the instrument deflection for the following dose rate 1 10 102 10 10 and 10 uSv h J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 11 2009 02 18 3 4 Software calibration When the instrume
8. or been burnt too many times Restart the instrument and try to change the calibration factor If it not work change the CPU 3 6 Neutron calibration The following equipment is needed neutron source for example 100 GBq Am Be oscilloscope 30 MHz pulse counter minimum 10kOhm put gamma source for example 2000 GBq Cs 137 It is supposed that a thorough electric calibration has been performed before this calibration is done Procedure J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 12 2009 02 18 1 Perform 3 measurements from different distances Check the dose rate on the LCD and or external pulse output Fine adjusts the amplification with P1 if necessary 2 Put the instrument beside a gamma source Cs 137 so you get the dose rate 2 Gy h Adjust the discriminator pot R16 on the ratemeter board so that the deflection is less than 5 uSv h to secure gamma insensitivity Note If the neutron dose rate sensitivity is checked against a known neutron source one has to remember that the contribution from scattered neutron radiation must be attended to 1f not special arrangements have been taken to avoid this in other case it can cause at least a 25 misreading above the theoretical dose value J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 13 2009 02 18 4 SPECIFICATIONS Microprocess
9. CE MANUAL WEDHOLM MEDICAL AB 2009 02 18 5 5 Countloss 19 5 6 Block diagram 5 7 Typical plateau curve 5 8 Adjustment of sensitivity 5 9 Presentation board Appendices normally not included can be delivered at request Presentation Card 29 29 Display Card H V Card 59 Upon delivery BFs manufacturing certificate Function test certificate Neutron calibration certificate Electric diagram digital part 20 2 22 23 C 321 207 1 Electric diagram analogue part C 321 208 1 Component location Electric diagram Component location Electric diagram Component location J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw C 321 214 1 C 321 209 1 C 321 213 1 C 321 210 1 C 422 764 1 WEDHOLM MEDICAL AB 2222 A SERVICE MANUAL 2009 02 18 1 NEUTRONMONITOR 2222A 2511 375 Oe Figur 1 1 Neutron Monitor 2222 A J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw 1 WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 2 2009 02 18 2 DESCRIPTION 2 1 Function description The circuit board marked Presentation card is the main board with collection and amplification of the pulses from the detector and a microprocessor part with presentation of the collected readings Usually when the battery or the external power is connected M will be 4 5 Volt 5V is generated by IC17 which gets 5V from IC15 2 1 1 Start up Normally when there is eit
10. WAY NEUTRON MONITOR 2222A Service Manual Wedholm Medical AB SE 611 29 Nyk ping Phone 46 155 28 03 70 Fax 46 155 26 31 10 e mail info wedholmmedical se http www wedholmmedical se WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 2009 02 18 Contents Page 1 NEUTRONMONITOR 2222A 2 DESCRIPTION PAR Function description 2 1 1 Start up 2 2 1 2 Trouble shooting start up 2 1 3 Instrument operation 2 1 4 Pulse collection 2459 Menu selection 2 1 6 Voltage alarm 2 1 7 Data collection 2 1 8 Memory print out 2 1 9 Trouble shooting printout 2 1 10 PC communication 2 1 11 Trouble shooting PC communication 2 1 12 Background lighting 2 1 13 Trouble shooting backeround lighting 2 1 14 Summer 6 2 1 15 Trouble shooting summer 2 1 16 HV setting 7 2 1 17 HV trouble shooting 2 1 18 Trouble shooting analogue part 2 1 19 Trouble shooting CPU input 2 1 20 External Signal output 2 1 21 Trouble shooting detector 2 2 Electronics 9 3 MAINTENANCE 3 1 Amplifier check 3 2 Discriminator check 3 3 Check of LCD deflection 3 4 Software calibration 3 5 Trouble shooting software calibration 3 6 Neutron calibration 4 SPECIFICATIONS 5 FIGURER 5 1 Detektorunit 15 5 2 Neutronsensitivity 5 3 Angeldependence 5 4 Neutronsensitivity J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw ON O N Un CA BW 9 SN N OO N 10 10 10 10 11 11 11 13 15 16 17 18 2222 SERVI
11. al and T3 transforms it to TTL level From here the TTL pulse goes to J4 for external purposes and further to the CPU pin 27 The programme is designed in a way that when there is a pulse on IC2 27 an internal register counts one step This is an 8 bit register and when it has reached 255 pulses it is set to zero and initiates an interrupt which in turn counts up another register After 10 ms there is a new interrupt which adds the total number of pulses during these 10 ms with the total number of pulses since the start of the measurement At the same time the two registers are set to zero and the measurement is restarted 2 1 5 Menu selection Pressing INT PRT will take you to a menu loop that can be used to set the date to erase the memory or set an alarm The menu which automatically comes up is dAtE INT Alternates between the three menus PRT To select press the PRT button Light button In the main loop you can exit the menu at any time and return to monitoring by using this button Note If this menu is selected you should avoid carrying out important integral measurements at the same time since the CPU can detect that INT has been activated shortly before you press PRT and it will terminate the integral measurement 2 1 5 1 Real time clock The real time clock IC10 is reached by choosing dAtE in the menu All information relating to the built in real time clock is saved in the following format 970114 15 10 i e ten
12. ard a number of things can be wrong 1 Check that SW2 is in position ON 2 Measure that IC16 delivers about 4 5 V 3 Check that the same voltage comes in to J1 on the HV board J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 8 2009 02 18 Note If both poles on SW3 are in position ON the high voltage will be much higher than normally Switching of the SW3 1 or 2 with power on can generate too high voltage and damage the detector or other components 2 1 18 Trouble shooting analogue part If at application of electric pulses on C16 there are no pulses on the LCD probably one of the OP amplifiers IC 11 14 or the pulse input PA7 on IC2 is damaged 2 1 18 1 Trouble shooting OP amplifier IC14 can be examined by applying TTL pulses in the joint IC13 R17 C23 and C24 this time with ground connection between the pulse generator and the instrument IC13 can be examined by applying 0 1 V p p pulses with ground connection in the joint C21 and R14 and examine the pulse train at IC13 6 IC12 and IC11 can not be tested electrically as the signals from the detector part still are so low 2 1 19 Trouble shooting CPU input Apply for example 3600 cps TTL pulses on PA7 IC2 from a pulse generator Because of T3 s transistor output PA7 IC must be tested without ground connection i e only pulses on the input If the instrument presents mSv h the input is working Note that as no groun
13. d is connected the number of pulses will not correspond to mSv h related to 1 pulse 1 39 If this relation shall be tested in this way the collector of T3 and R25 must be soldered away and ground connector be used 2 1 20 External Signal output The pulses sent out to the CPU can be checked through the external SIGNAL OUT The difference between these pulses and what is presented on the LCD is the conversion factor of 1 39 and the software calibration factor The Signal out is controlled by the software Normally the Signal out is disabled too increase the lifetime of the battery To enable disable the Signal Out choose Por in the setup menu 2 1 21 Trouble shooting detector If the electric calibration is performed and working but there are no pulses at neutron calibration something is wrong with the detector unit Check that there is HV to the detector If there is HV J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 9 2009 02 18 it is easiest to exchange the detector as there is not possibility to test the detector in any other way 2 2 Electronics A block diagram on the instrument is shown in Figure 5 6 Drawings for the presentation board are C 321 207 C 321 208 and C 321 214 and for the display board C 321 209 and C 321 213 The pulses from the detector are amplified in the pulse amplifier and the discriminator level is set on a level which discriminat
14. es the noise and gamma pulses meaning a standard pulse out for each incoming neutron pulse The standard pulse is mated to a micro controller type Motorola 68HC11 that calculates and presents the pulses in mSv h and as an option also the dose in uSv or mSv The standard pulses are available on the ratemeter board and on the BNC connector PULSE OUT which are taken out through connector J4 on the presentation board The HV source consists of a constant voltage source a DC AC transformer a HV transformer and a cascade rectifier see drawing C 321 210 and C 422 764 With the switch SW3 the HV can be changed in three steps 2400 2500 and 2600 V to verify that the HV plateau is correct see Figure 5 7 The same function is used for compensation of HV deflection at extremely low temperatures The HV can be switched off with SW2 without influencing the rest of the electronics J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 10 2009 02 18 3 MAINTENANCE 3 1 Amplifier check Turn the 5K potentiometer P1 to the center position Test pulses with negative polarity shall be fixed to pin J3 on the presentation board through a connection board according to Figure 5 8 The charge applied through the capacitor is U 1 10 Coulombs where U is the test pulse amplitude in volts The output pulse from the op amplifier IC13 pin 6 see figure 5 8 testpoint amplifier and drawing on Adjustments
15. h I LLL COLS TD EI IL LLL 1 on 1 TIE CERTE T HIE LI HIM LUE CUL J kk 8341 LIH HL HL ILE i SSH CEN su Su WE HH THE 5 sce DIET EHE TED EH Neutron sensitivity cps per Jk Sv h 8 909 10 Neutron energy eV Figure 5 4 Difference from ideal response J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw eee LEE IL SERVICE MANUAL L ET IL LIT 18 2222 SERVICE MANUAL 19 WEDHOLM MEDICAL AB 2009 02 18 5 5 Count loss Measured dose rate mrem h 232122122432 205225321 Tur XE z 10006 o uw Figure 5 5 NEUTRON MONITOR 2222 A Count loss at varying pulse repetition frequencies J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 20 2009 02 18 5 6 Block diagram External Power Battery eliminator option 6 1 5 V Batteries High voltage board
16. her battery or external supply the voltage over M is about 4 5 V This voltage is up to the ON OFF button on the membrane panel and supports back up voltage to RAM IC5 and the real time clock IC10 If both the battery and the external support should fail the back up battery BAT takes over and supports RAM and clock It is not possible to start the instrument with only the back up battery when D8 acts as stop for the battery against the voltage regulators IC15 amp 16 When ON OFF on the panel is pressed the M voltage reaches the CPU IC2 pin 34 at the same time as M saturates the transistor T4 which grounds pin 5 at IC15 amp 16 This pin is shutdown for the regulators i e as long as it is above 0 3 V there is no voltage out although the battery voltage is on the input When these shutdown pins are grounded the regulators start and generate 5 V to the CPU and analogue part IC15 and 5V to the HV IC16 if SW2 is set When the CPU receives 5V feeding from IC15 It starts and reacts on the ON OFF push this happens so fast that the program starts before the ON OFF button is released through pin 34 and it puts pin 29 high which takes over the feeding of T4 and IC15 amp 16 and the instrument is working 2 1 2 Trouble shooting start up If the instrument fails to start when pushing ON OFF there are some alternatives for trouble shooting J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL
17. me clock This circuit is totally independent as long as the CPU does not try to change its settings It updates time and date and presents these for the CPU when asked for At start up all display segments first are lit up during 5 seconds for the operator to be able to see that all segments work After that the version number of the programme is shown This is also for the high voltage to stabilise and to avoid disturbance pulses from the loading process After this initiation the instrument actively starts to present the neutron flow by collecting pulses from the detector at IC2 27 and then present them In ratemeter mode the measurements are updated every 2 seconds in dose rates above 0 05 mSv h Below 0 05 mSv h there is an update 10 seconds If the integral mode is chosen the dose is updated every 100 seconds 2 1 4 Pulse collection The discharges of at least 5 10 Coulomb generated in the detector are transported on the HV by pin J3 to C16 After C16 only the pulses remain The pulse is then amplified 11 times through IC11 By adjust P1 in the feedback of IC12 the amplitude of the pulse can be set The spectra can be inspected on IC13 6 J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 4 2009 02 18 T1 and P2 set the discriminator level i e what levels to be removed to avoid noise and gammapulses This is inspected on D5 IC14 and T2 transforms the pulse to a AV sign
18. minutes past three in the afternoon of January 14 1997 When you select this menu three figures will be displayed which in normal cases display the rate meter value 00 1 Where the two on the left are date time and the right is a control figure as shown in Table 2 1 the year e g 97 2 the month e g 01 3 the day e g 14 4 the hour e g 15 5 minutes before or after the hour e g 1 Table2 1 X Setting the date Use the following buttons to change the setting J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 5 2009 02 18 INT Increases the figure on the left i e by ten years months etc PRT Increases the figure on the right i e by one year month etc Light button Confirms that the right value is entered which causes the program to move forward to the next entry When confirming the minutes it returns you to the main menu 2 1 5 2 Trouble shooting real time clock If the real time clock does not take up the input value it can only be checked if there is more than 2 V when the instrument is shut off on IC10 20 If not the back up battery is empty and there are no data in the RAM memory As the M is operating the clock it should work as long as the instrument works disregard the status of the back up battery If it seems like the clock unit is faulty first investigate it the crystal oscillator gives 32 768 kHz This is easier to exchange as it
19. nt has been calibrated with known pulses and a measurement with a known neutron source shows a certain deviation a software factor can be added The software factor is initiated to 1 00 This calibration factor is burnt into the internal EEPROM of the microcomputer and is reached by activating switch 1 at SW1 on the presentation board The calibration value 01 00 and the current integrated dose 514 9 uSv are shown on the LCD 01 00 514 9 uSv Always wait with calibration until the first dose value after 100 seconds Increase the calibration factor with INT and decrease with PRT The dose will be updated all the time with the new calibration factor Finish by deactivating SW1 1 and switching the monitor off on The new calibration value will be burnt into the EEPROM Note 1 If this factor deviates from 1 00 the value on the display will deviate from the value which can be calculated by counting the number of pulses on the BNC connector SIGNAL OUT as these pulses are taken out before the microcomputer Note 2 If the light button is pushed when SW1 1 is activated the background light is not switched off as both these functions are handled by interrupts If the light button has been pushed SW1 1 must be deactivated and the instrument switched off 3 5 Trouble shooting software calibration If the Instrument does not seem to update the dose value with a new calibration factor probably the EEPROM of the microprocessor has been destroyed
20. od and the instrument will give an audible alarm 0 025 eV 17 MeV 0 35 0 50 cps uSv h individual variation 2 gives lt 5 uSv h 5 10 Coulomb 2V 10 Coulomb 1 us WEDHOLM MEDICAL AB Discriminator range External pulse port Amplitude Duration Load HV supply Voltage Operation Power supply Internal Operating time Battery testing External option Temperature range Dimensions Diameter Length Weight 2222 2009 02 18 SERVICE MANUAL 14 About 0 5V 3V about 2 8V 500 ns 10 kohm min 2200V 2700V 1 V C Alkaline batteries 6 x 1 5V IEC LR14 80h Tested electronically LO BATT lights up at the LCD when there is about an hour left of battery capacity Through the External Power connector an eliminator which will take over the battery function can be connected This eliminator can be connected and disconnected while the instrument is operating 10 C 40 C 215 mm 325 mm 10 5 kg including batteries The exact value depends on the neutron calibration The exact value depends on the individual BF3 tube HV is normally 2400V at plateau knee J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw WEDHOLM MEDICAL AB 2222 SERVICE MANUAL 15 2009 02 18 5 FIGURES 5 1 Detector unit DETECTOR UNIT ELECTRONIC UNIT NEUTR N REM COUNTER Ftio mm QUO p m gh om m
21. or Motorola 6SHC11 Software C code stored in external EPROM Real time clock Display Display of dose rate Analogue display Digital display Storage of values Printing Statistical error Energy range Neutron sensitivity Gamma sensitivity Minimum pulse charging from detector HV 2500 V Charge amplification Amplification Differentiation time J Gemensam Manualer Digipig 2222 Servicemanual engelska 1_11 doc akw Can be set by the user Displays the date and time in the following format 970417 14 41 The backup battery ensures that the clock continues to work even during battery replacement Graphic LCD with optional background lighting at 4 second intervals Logarithmic scale in the range of 0 001 100 mSv h If the value exceeds 100 mSv h the instrument will display 100 mSv h In the range of 0 001 999 9 mSv h above 999 9 mSv h 999 9 and OVERFLOW will blink with a frequency of 1 Hz Every 5 minutes the dose rate value is stored in an external RAM with a spill over function The entire memory can be erased The backup battery ensures that the measurement value is stored even during battery replacement Via RS 232 to terminal program Printout from the memory of the measuring values with time indication LO BATT ALARM and OVERFLOW indication are printed out with time indication Maximum 20 At entrance in a weak neutron field the error can be higher during a short peri
22. rom IC16 on the presentation board runs the HV That voltage can be varied through the components P3 SW3 R36 R39 Voltage out can be adjusted with the formula Vout IC16 1 22 R1 R2Y R1 Where R2 in this case is R36 and R1 is the components P3 R37 and R38 R39 i e everything between IC16 VSET and ground This leads to that SW3 affects the value of R1 which affects the voltage over J6 in three firm steps These levels are there to set HV fast between 2400 2500 and 2600 V As the HV is proportional to the voltage on J6 it can be set before the HV board is connected Rough adjustment of the HV 1 Connect a voltmeter between J6 pin 1 and 6 and ground 2 Turn both SW3 connectors in position OFF 3 Turn SW2 on 4 Adjust P3 until the voltmeter shows 4 35 V corresponding 2400V 5 Turn SW3 on 1 and check that the voltmeter shows 4 5 V corresponding 2500 V 6 Turn SW3 1 off and SW3 2 on and check that the voltmeter shows 4 7 V corresponding 2600 V The HV can be measured on the soldering pin J7 on the presentation board see figure 5 9 Note Use high ohm or electrostatic voltmeter Warning HV is on both soldering pins on the presentation board and HV capacitors Depending on that the load resistance 1s very large about 100 Gohm the HV remains for a while after the instrument has been turned off Caution must be taken when removing the cover 2 1 17 HV trouble shooting If there is not about 2 5 kV from the HV bo
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