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Ludlum Measurements 375-31H, Manual

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Models 375-31H Area Monitor with Neutron Detector

 

 

 

 

Ludlum Measurements, Inc. 

 

January 2021 

Analog Output 

7-2 

Discriminator 

7-2 

Battery Charge 

7-3 

Calibrating Detector 

7-3 

Operating Voltage Plateau 

7-3 

Gamma Rejection Check 

7-4 

Conversion Check 

7-4 

Recycling 

  8 

Parts List 

  9 

Model 375 Digital Wall-Mount Area Monitor without Detector 

9-1 

Model 375 Series One without Detector 

9-1 

Main Board, Drawing 558 x 1 

9-1 

Wiring Diagram, Drawing 558 x 136 

9-6 

Model 42-31H Neutron Detector 

9-6 

Drawings and Diagrams 

10 

Summary of Contents for 375-31H

Page 1: ...LUDLUM MODELS 375 31H AREA MONITOR WITH NEUTRON DETECTOR January 2021 Serial Number 278020 and Succeeding Serial Numbers ...

Page 2: ...LUDLUM MODELS 375 31H AREA MONITOR WITH NEUTRON DETECTOR January 2021 Serial Number 278020 and Succeeding ...

Page 3: ...Models375 31HAreaMonitorwithNeutronDetector Ludlum Measurements Inc January 2021 ...

Page 4: ...uding without limitation any implied warranty of merchantability or fitness which extend beyond the description of the face there of If the product does not perform as warranted herein purchaser s sole remedy shall be repair or replacement at the option of Ludlum Measurements In no event will Ludlum Measurements be liable for damages lost revenue lost wages or any other incidental or consequential...

Page 5: ......

Page 6: ...ration cover 4 2 RS 232 Output 4 3 9 Pin Remote Data Connector 4 3 9 Pin Relays Connector 4 4 Common Options and Modifications 5 Relay Options 5 1 Ethernet Interface Option 5 5 Time and Date Stamp Option 5 5 Printer DIP Switch Settings 5 6 Sigma Alarm Modification Option 5 7 4 to 20 mA Isolated Output Driver Option 5 8 Safety Considerations 6 Environmental Conditions for Normal Use 6 1 Cleaning In...

Page 7: ...g Detector 7 3 Operating Voltage Plateau 7 3 Gamma Rejection Check 7 4 Conversion Check 7 4 Recycling 8 Parts List 9 Model 375 Digital Wall Mount Area Monitor without Detector 9 1 Model 375 Series One without Detector 9 1 Main Board Drawing 558 x 1 9 1 Wiring Diagram Drawing 558 x 136 9 6 Model 42 31H Neutron Detector 9 6 Drawings and Diagrams 10 ...

Page 8: ...tive indication of instrument operation Parameters are protected under a calibration cover Calibration is easily accomplished by moving the cal dipswitch to the right and using the pushbuttons to increment or decrement the calibration constant dead time correction and alarm point parameters Parameters are stored in non volatile memory retained even with power disconnected The user friendly digital...

Page 9: ...located polyethylene sphere surrounding the 3 He detector A study has demonstrated that the 9 inch cadmium located sphere has a response similar to that of a 10 inch dimeter rem responding sphere See Section 2 for more information on the detector A five decade logarithmic analog output is provided A battery backup provides 48 hours of additional use after the primary power is removed ...

Page 10: ...odel 375 31H comes equipped with a neutron detector The neutron detector is designed to detect thermal and fast neutrons 0 025 eV to approximately 12 MeV Neutrons are detected indirectly through nuclear reactions which result in energetically charged particles It utlizies this reaction in the form of helium 3 3He which fills the gas proportional tube on the detector Gamma rejection is very good re...

Page 11: ... display the current radiation reading and begin checking for an alarm condition Checking Parameters Check the low alarm point setting by pressing the LOW ALARM button The low alarm point will be displayed as long as the button is pressed The low alarm point is in units of units The low alarm point can be set from 0 1 units to 9999 units Check the high alarm point setting by pressing the HIGH ALAR...

Page 12: ... Changing alarm points is done by holding down the corresponding parameter key and pressing the up or down arrow buttons Alarm points can be set in the range of 0 1 to 9999 When an alarm point is changed the instrument will sound an audible beep to confirm the saving of the parameter and will then return to displaying the current radiation level Note Once the alarm point s is set it is important t...

Page 13: ...f detector used Response typically 3 seconds from 10 to 90 of final reading Status green light indicates the instrument is functioning properly Low Alarm indicated by a yellow light and slow beep 1 per second audible tone can be set at any point from 0 0 9999 00 00 9999 for Series One High Alarm indicated by a red light and a fast beep 4 per second audible tone can be set at any point from 0 0 999...

Page 14: ...ge adjustable from 450 2500 volts Dead Time adjustable to compensate for dead time of the detector and electronics can be read on the display Overload a display reading of OL and audible FAIL alarm indicate detector saturation It is normally set to initiate just above the highest range of the detector Over range A display reading of and activated low and high alarms indicate that the radiation fie...

Page 15: ...ltage connection Frequency is approximately 3 kHz Power 9 Vdc wall mount adapter handles any mains voltage in the world supplied with four sets of prongs for almost any style wall receptacle Battery Life typically 48 hours in non alarm condition 12 hours in alarm condition Battery Charger battery is continuously trickle charged when the instrument is connected to line power and turned on Warning O...

Page 16: ...ng 2 mV input sensitivity Sensitivity 100 cpm mrem hr 241 AmBe fast neutrons Gamma Rejection 10 cpm or less through 10 R hr 100 mSv hr 137 Cs Detection Range thermal to approximately 12 MeV Energy Response thermal to 12 MeV follows the radiation protection guide curve for neutron dose Input Sensitivity 2 mV Operating Voltage approximately 1200 V Connector series C others available Temperature Rang...

Page 17: ...nown point at some given reading HV used to set the high voltage required for detector operation Adjustable from 450 2500 Vdc The high voltage required will depend on the type of detector used Internal GM detectors typically require 550 Vdc Be sure to check the high voltage with a high impedance 1000 Mohm impedance voltmeter only A high voltage checkpoint is located next to the HV potentiometer DI...

Page 18: ... too erratic leaving this switch in the calibration mode during operation will help Moving the CAL MODE switch back to the left locks the parameters and disables any further changes Dipswitch 2 The second switch LATCH ALARM changes the high alarm to a latching alarm This switch does not affect the low alarm which is always non latching When switched to the left the high alarm is non latching the a...

Page 19: ...condition of the status lights The data is presented in the following format RS 232 Output With the CAL MODE dipswitch in the left position the Model 375 31H dumps RS 232 data onto pin 4 of the 9 pin connector every two seconds 9 Pin Remote Data Connector female sockets The 9 pin connector provides output signals from the instrument and input voltage to the instrument The pin assignments are pin1 ...

Page 20: ...e pins The 9 pin relay connector provides a Form C common normally open and normally closed contact for the three fail safe relays of LOW ALARM alert HIGH ALARM and FAIL The pin assignments are shown energized pin1 FailNO pin2 FailNC pin3 AlertCOM pin4 AlarmNO pin5 AlarmCOM pin6 FailCOM pin7 AlertNO pin8 AlertNC pin9 AlarmNC ...

Page 21: ...ditional relay options are available at extra cost Form C Relay 3 pin connector added PN4558 036 This option allows the user to access the fail safe form C contacts normally open normally closed and common which activate upon HIGH ALARM This is achieved by using an additional 3 pin connector with male pins located at the bottom of the instrument wired in parallel with the 9 pin D male pin connecto...

Page 22: ... This option includes a small enclosure connected to the Model 375 via a short cable that accepts a standard mains power cord conduit option is 4558 038 1 In an ALARM condition the mains voltage is relayed to a set of terminals Only a licensed electrician should install this option Figure 1 Mains Relay Box Back Panel See below for description of noted parts in drawing above A connector for cable P...

Page 23: ...uary 2021 Figure 2 Mains Relay Box Front Panel See below for description of noted parts in drawing above A conduit connector to the box if necessary B AC receptacle removed if using conduit C mains relay output 3 pin connectors D optional extra output E relay output for conduit if necessary ...

Page 24: ...ee below for description of noted parts in drawing above A 110 220 Vac conduit AC input H hot and N neutral For 220 Vac H L1 and N L2 B relay output H hot and N neutral For 220 Vac H L1 and N L2 C optional conduit connector input D optional relay output for conduit Strobe lights and or horns are also available through Ludlum Measurements ...

Page 25: ...ll need the following a Model 375 31H instrument a CBM 910 40 column printer and a cable 8558 142 The printer should be configured at 2400 bps baud no parity 8 data bits 1 stop bit and no handshaking See printer manual for proper setup instructions Setting the date and time Check the month and day MMDD by pressing the LOW ALARM and HIGH ALARM buttons simultaneously The month and day will be displa...

Page 26: ...e 20H Byte 11 M Byte 28 A Space Byte 12 Byte 29 L F Byte 13 D Byte 30 A OR A Byte 14 D Byte 31 R I Byte 15 Byte 32 M L Byte 16 Y Byte 33 Carriage Return 0DH Byte 17 Y Byte 34 Line Feed 0AH Example Output 0642 1 04 21 95 16 56 24 ALARM 0000 0 04 21 95 08 32 16 FAIL Printer DIP Switch Settings Citizen Dot Matrix Printer Model CBM 910 Type II Please refer to page 32 of the printer user s manual for t...

Page 27: ...tion level in cps counts per second The sigma alarm point is then BKGND x sigma square root of BKGND The HIGH ALARM has not been changed it is still a fixed alarm point and will be activated when the radiation level exceeds that setpoint This feature allows the sigma alarm to trigger quickly if a small amount of radiation is present and allows the fixed alarm to warn that the background radiation ...

Page 28: ...viding an isolated 4 to 20 mA output capability The circuit has an internal loop supply generating 12 Vdc from the RAWDC of the Model 375 31H It is designed for a 2 wire configuration with one conductor carrying the 4 20 mA current signal and the second conductor providing a return isolated loop ground See Wiring Diagram Figure 4 below Figure 4 Wiring Diagram Decade Base Display mA Value 0 0 1 4 m...

Page 29: ...hat displays values to two decimal places the 4 20 mA output starts a decade lower from 0 01 to 0 1 units with the highest decade being 100 to 1000 units The full scale output of 20 mA can be adjusted for a reading of 1000 units The highest displayed range of 1000 to 10 000 units then has a constant 20 mA output SPECIFICATIONS Power Required 7 5 Vdc at 100 mA minimum Vin 5 5 V and maximum Vin 15 V...

Page 30: ...s or RESET the Model 375 Check for a voltage of 1 00 V 5 across Rterm typically a 250 ohm V 0 004 X Rterm terminating resistor The resistor should be placed between Pin 5 the 4 20 mA output and Pin 6 Loop ground Note Loop ground is isolated from instrument ground Now apply a full scale meter reading to the analog input or move the CAL dipswitch to the right Note Instrument ground is not the same a...

Page 31: ...l mounted DC adapter supplying 9 12 Vdc Maximum transient voltage of 1500 Vac Installation Category II Overvoltage Category as defined by IEC 1010 1 Pollution Degree 2 as defined by IEC 664 Cleaning Instructions and Precautions The Model 375 31H may be cleaned externally with bleach wipes or with a damp cloth using water Lysol or alcohol as a wetting agent Do not immerse the instrument in any liqu...

Page 32: ...URRENT DC IEC 417 No 5032 designates an input receptacle that accommodates a power cord intended for connection to DC voltages This symbol appears on the side panel PROTECTIVE CONDUCTOR TERMINAL per IEC 417 No 5019 designates the central grounding point for the safety ground This symbol is visible inside the chassis CAUTION per ISO 3864 No B 3 1 designates hazardous live voltage and risk of electr...

Page 33: ... within the European Union Electrical Safety Precautions Warning Observe the following instructions to avoid a potentially hazardous situation which if mishandled could result in death or serious personal injury as well as property damage Do not expose the unit to rain or an environment where it may be splashed by water or other liquids as doing so may result in fire or electric shock Use the unit...

Page 34: ...age Detector Connector Warning Potential electrical shock hazard do not touch the center pin of the detector connector unless the unit has turned off and power has been removed for at least one minute Battery Replacement Warning Only certified technicians or calibration personnel should replace battery Note Ludlum Measurements Inc recommends replacing batteries every four years ...

Page 35: ...only be changed while in calibration mode Switch the top dipswitch CAL MODE to the right to switch into calibration mode Changing any parameter is done by holding down the parameter key and pressing the up or down arrow buttons Any parameter can be set in the range of 0 1 to 9999 If a parameter is changed the instrument will beep to confirm the saving of the parameter and then return to displaying...

Page 36: ...ut is a five decade logarithmic voltage out The maximum voltage out while under primary power is 6 volts The maximum voltage out while under battery backup power is 4 5 volts The five decades are 0 1 units 1 0 units 1 units 10 units 10 units 100 units 100 units 1000 units 1000 units 10000 units When the CAL MODE dip switch is switched to the right the analog output goes to full scale The analog ou...

Page 37: ...on check Operating Voltage Plateau 1 Connect the detector to a Model 2200 2 Set Model 2200 input sensitivity to 2 mV 3 Expose the detector to a 20 mrem hr 241 AmBe neutron source 4 Run a plateau as follows Taking one minute counts record the count rate for 25 volt incremental steps from 1000 volts through a region in which the count rate steadily increases becomes relatively constant flattens out ...

Page 38: ...0 R hr 137 Cs gamma radiation field 3 Take a one minute count If more than 10 counts are observed for the one minute period decrease the operating voltage until the count rate drops below 10 cpm however ensure that the HV remains in the plateau region determined above 4 Ensure that sensitivity for the selected operating voltage is approximately 120 cpm mrem hr 5 Return the detector to the moderato...

Page 39: ...Models375 31HAreaMonitorwithNeutronDetector Section7 Ludlum Measurements Inc Page 7 5 January 2021 Ref Point mrem hr Reading cpm Range Scale 400 200 80 20 8 2 ...

Page 40: ...other but simply desires to inform its consumers of the range of recyclable materials present in its products so that the user will have flexibility in following all local and federal laws The following types of recyclable materials are present in Ludlum Measurements Inc electronics products and should be recycled separately The list is not all inclusive nor does it suggest that all materials are ...

Page 41: ...4 C4 100µF 16V 04 5794 C5 C6 10µF 25V 04 5728 C7 100µF 16V 04 5794 C8 10µF 25V 04 5728 C9 C11 100µF 16V 04 5794 C12 C21 0 1µF 500V 04 5696 C22 C23 0 01µF 3kV 04 5762 C24 C33 0 1µF 500V 04 5696 C35 100pF 100V 04 5743 C36 10µF 25V 04 5728 C37 100pF 100V 04 5743 C38 100µF 16V 04 5794 C39 C40 10µF 25V 04 5728 C41 C43 10µF 25V 04 5655 C44 C53 0 1µF 25V 04 5744 C54 10µF 25V 04 5655 C55 C56 0 1µF 25V 04 ...

Page 42: ...µF 25V 04 5655 C722 0 001µF 100V 04 5659 C731 100pF 3kV 04 5735 Q1 Q3 2N7002L 05 5840 Q4 CMXT3904TRLF 05 5888 Q5 CMXT 3906TRLF 05 5890 Q6 CMXT3904TRLF 05 5888 Q7 2N7002L 05 5840 Q151 Q154 2N7002L 05 5840 Q321 Q322 2N7002L 05 5840 Q331 MJD200RLG 05 5844 Q431 2N7002L 05 5840 VR341 LT1129CQ 5 06 6372 U2 MAX985EUK T 06 6459 U3 LT1304CS8 06 6394 U4 ICL7660SCBAZ 06 6437 U5 TCM810LVNB713 06 6424 U31 SA08...

Page 43: ...7 6353 CR4 CR5 US1M E3 07 6530 CR6 P0640SCMCLRP 21 9028 CR7 CR10 US1M E3 07 6530 CR11 P0640SCMCLRP 21 9028 CR12 MMBD914LT1G 07 6353 CR13 CR14 US1M E3 07 6530 CR15 CMSH1 40M 07 6411 CR16 MMBD914LT1G 07 6353 CR17 CR21 P0080SC 21 9004 CR22 CR31 CMPD2005SLF 07 6468 CR32 CMSH1 40M 07 6411 CR33 CR34 CMPD2005SLF 07 6468 CR35 CMSH1 40M 07 6411 CR36 P0080SC 21 9004 CR38 US1M E3 07 6530 CR341 CR342 CMSH1 40...

Page 44: ...2ohm 5 250mW 12 7932 R18 82 5K 1 250mW 12 7849 R19 R22 2 2ohm 5 250mW 12 7932 R23 100K 1 250mW 12 7834 R24 1M 1 250mW 11 7251 R25 10ohm 1 125mW 12 7836 R26 100ohm 1 100mW 12 7142 R27 100k 5 333mW 12 7747 R41 2 2ohm 5 250mW 12 7932 R42 60 4ohm 1 250mW 12 7962 R141 2 2ohm 5 250mW 12 7932 R142 60 4ohm 1 250mW 12 7962 R151 R152 100K 1 250mW 12 7834 R201 24 3K 1 250mW 12 7867 R241 2 21K 1 250mW 12 7835...

Page 45: ... 7877 R723 1K 1 250mW 12 7832 R724 4 75K 1 250mW 12 7858 R732 R733 100K 1 250mW 12 7834 R735 10K 1 250mW 12 7839 RN411 220K 12 7831 P1 RAPC712 13 8445 P2 640457 3 BAT 13 8165 P3 FRJAE 468 LF 21 9007 P4 9 PIN D CONN 747197 4 13 8364 P5 640456 3 MTA 100X4 ETHERNET 13 8088 P6 747020 2 9 PIN D FEMALE 13 8555 P7 640456 3 MTA 100X3 4 20mA 13 8081 P8 640457 4 MTA 100X4RA SONALERT 13 8089 P9 640456 3 MTA ...

Page 46: ... 21 9705 UNIT Completely Assembled Model 42 31H Neutron Detector 47 3583 Model 42 31H SPHERE ASSY 47 1345 FOOT BRACKET 7005 084 9 inch BALL 7002 097 MOUNTING RING 7005 101 RIGHT HANDED INST MOUNTING BRACKET 7363 246 LEFT HANDED INST MOUNTING BRACKET 7363 247 MODEL 42 31H PROBE ASSY 4005 140 3 He TUBE 25185 2 ATM 01 5793 CONNECTOR UG706 U 4478 011 TUBE BODY ASSY 2005 092 MODEL 42 30 42 31 DETECTOR ...

Page 47: ...eutronDetector Section10 Ludlum Measurements Inc Page 10 1 January 2021 Drawings Main Circuit Board Drawing 558 x 1 5 sheets Main Circuit Board Component Layout Drawing 558 x 2A 2 sheets Wiring Diagram Drawing 558 x 136 Section 10 ...

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