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MODEL 2224-1 

Technical Manual   

 

Section 8

 

Ludlum Measurements, Inc. 

Page 8-1 

January 2012 

 

 

 

Troubleshooting 

 

ccasionally  you may encounter problems with your LMI 

instrument or detector that may be repaired or resolved in the 

field, saving turn-around time and expense in returning the 

instrument to us for repair. Toward that end, LMI electronics 

technicians offer the following tips for troubleshooting the most common 

problems. Where several steps are given, perform them in order until the 

problem is corrected. Keep in mind that the most common problems 

encountered with this particular instrument are: (1) detector cables, (2) sticky 

meters, (3) battery contacts. 

Note that the first troubleshooting tip is for determining whether the 

problem is with the electronics or with the detector. A Ludlum Model 500 

Pulser can be invaluable at this point because of its ability to simultaneously 

check high voltage, input sensitivity or threshold, and the electronics for 

proper counting.  

We hope these tips will prove to be helpful. As always, please call if you 

encounter difficulty in resolving a problem, or if you have any questions.  

Troubleshooting Electronics that utilize 
Proportional and Scintillator Type Detectors 

 

SYMPTOM 

 

No power (or meter 

does not reach 

BAT 

TEST

 or 

BAT OK

 

mark) 

 

POSSIBLE SOLUTION 

 

1.

 

Check batteries and replace if weak.  

 

2.

 

Check polarity (see marks inside 

battery lid). Are the batteries installed 

backwards? 

Section 

Summary of Contents for 125559

Page 1: ...LUDLUM MODEL 2224 1 SCALER RATEMETER January 2012 Serial Number 125559 and Succeeding Serial Numbers ...

Page 2: ...LUDLUM MODEL 2224 1 SCALER RATEMETER January 2012 Serial Number 125559 and Succeeding Serial Numbers ...

Page 3: ...anty 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 damages arising from the purchase use or...

Page 4: ......

Page 5: ...tion 2 3 Specifications 3 Description of Controls and Functions 4 Operator Controls 4 1 Internal Controls 4 2 Safety Considerations 5 Environmental Conditions for Normal Use 5 1 Cleaning Instructions and Precautions 5 1 Warning Markings and Symbols 5 2 Calibration and Maintenance 6 Calibration 6 1 Establishing an Operating Point 6 1 Meter Calibration 6 2 Detector Overload Calibration 6 4 Maintenan...

Page 6: ...ist 10 Model 2224 1 Scaler Ratemeter 10 1 Amplifier Power Supply Board Drawing 390 104 10 1 Processor Board Drawing 390 107 10 4 Calibration Board Drawing 390 112 10 4 Display Board Drawing 390 127 10 5 Interconnect Board Drawing 390 124 10 5 Wiring Diagram Drawing 390 110 10 5 Drawings and Diagrams 11 ...

Page 7: ...y or alpha and beta by selecting the corresponding toggle switch selection Audible click per event tones can also be selected to discriminate beta low pitch tone from alpha high pitch tone via the side mounted speaker Beta threshold window and alpha threshold are adjustable to optimize alpha beta efficiency and count separation A regulated high voltage power supply adjustable from 400 to 2000 volt...

Page 8: ...portant If multiple shipments are received ensure that the detectors and instruments are not interchanged Each instrument is calibrated to specific detectors and is therefore not interchangeable To return an instrument for repair or calibration provide sufficient packing material to prevent damage during shipment Also provide appropriate warning labels to ensure careful handling Include detector s...

Page 9: ... to the Instrument Caution The detector operating voltage HV is supplied to the detector via the detector input connector A mild electric shock may occur if you make contact with the center pin of the input connector Switch the Model 2224 1 to the OFF position before connecting or disconnecting the cable or detector Connect one end of a detector cable to the detector by firmly pushing the connecto...

Page 10: ...tween alpha and beta pulses from the radiation detector The detected alpha count is displayed by selecting the α position on the three position α α β and β toggle switch The sum of the alpha and beta counts are displayed in the α β position and beta counts are displayed in the β position Multiply the CPM reading on the analog ratemeter by the range multiplier position When using the LCD and count ...

Page 11: ...ume control located on front panel headset jack located on the instrument can High Voltage externally adjustable from 400 to 2000 Vdc Linearity within 10 of true value for the analog rate meter within 2 for the LCD Crosstalk no more than 10 of gross alpha counts in beta channel no more than 1 of gross beta counts in alpha channel Response Time 1 range multiplier 10 seconds 10 7 seconds 100 2 secon...

Page 12: ...nce instrument calibration change less than 3 to battery endpoint Battery Life exceeds 350 hours with a fresh set of alkaline D cell batteries Temperature Range 20 to 50 C 4 to 122 F Finish drawn and cast aluminum with beige powder coating Size 16 5 x 8 9 x 21 6 cm 6 5 x 3 5 x 8 5 in H x W x L Weight 1 6 kg 3 5 lb including batteries ...

Page 13: ...The LCD will then show 888888 display the processor program version and then 0 Liquid Crystal Display LCD six digit display that shows the scaler count for the selected channel The display also indicates when a count is in progress by displaying two colons The colons are turned off when the count is completed If the counter exceeds 999999 an arrow in the upper left corner of the display turns on t...

Page 14: ...the HV position is selected and provides a rapid means of driving the analog meter to zero when the RES position is selected Use the 0 2 kV meter scale for high voltage readings Count Pushbutton located in the carrying handle When depressed the counter is reset to zero and the timer is started Colons on the display indicate a count cycle is in progress Remove the CAL cover to access the following ...

Page 15: ...ha pulses cannot be heard in the beta only channel selection and beta pulse tones will not be heard in the alpha only channel selection Dipswitch 6 SPARE Not used The following controls are utilized during calibration only and should only be adjusted by a qualified calibrator MTR a multi turn potentiometer used to calibrate the meter to the CPM reading AT a multi turn potentiometer used to vary th...

Page 16: ...maximum HV limit to 2000 Vdc HV a multi turn potentiometer used to adjust the high voltage test reading to correspond with the actual high voltage output HV must be selected on the RES HV toggle switch during adjustment LB a multi turn potentiometer used to adjust the minimum battery voltage level corresponding to the low battery indication on the meter dial The range selector switch must be in th...

Page 17: ...tive pollution or dry nonconductive pollution becomes conductive due to condensation This is typical of industrial or construction sites Cleaning Instructions and Precautions The Model 2224 1 Scaler Ratemeter may be cleaned externally with a damp cloth using only water as the wetting agent Do not immerse the instrument in any liquid Observe the following precautions when cleaning 1 Turn the instru...

Page 18: ...ed to take the following precautions to avoid contact with internal hazardous live parts that are accessible using a tool 1 Turn the instrument power OFF and remove the batteries 2 Allow the instrument to sit for one minute before accessing internal components CAUTION RISK OF ELECTRIC SHOCK per ISO 3864 No B 3 6 designates a terminal connector that allows connection to a voltage exceeding 1 kV Con...

Page 19: ...er to the specific detector Operation Manual or calibration certificate for the suggested threshold and window settings Once the thresholds and window settings are established an operating voltage versus count rate plot should be performed for both alpha and beta count channels with alpha and beta particle emission sources The following procedure is an example of determining the operating voltage ...

Page 20: ...unt dip in the above step 675 volts start the plot at 625 volts and increase in 25 volt steps until 725 volts is reached Plot alpha source beta source and background counts for both the α and β channel positions 7 Find the optimum operating voltage from the plot which gives the greatest alpha and beta source efficiency while maintaining no greater than the maximum acceptable level of cross talk be...

Page 21: ...ous subsection Establishing an Operating Point 7 Connect high impedance high voltage meter may use the Model 500 Pulser if equipped with a HV meter and adjust the HV control for a reading of 1000 Vdc on the voltmeter 8 Depress the HV pushbutton and adjust the HV potentiometer located on the main circuit board for a reading of 1 0 kV on the meter dial Adjust the HV output from 500 to 1500 Vdc and c...

Page 22: ... alpha beta scintillators expose the detector photomultiplier tube PMT to a small light leak by loosening the detector window Some scintillation detectors incorporate a screw in the detector body which when removed will simulate a detector face puncture or light leak The meter should start to decrease toward zero as light saturates the scintillation material 3 Expose just enough light to where the...

Page 23: ...ning battery replacement or cable replacement Note Ludlum Measurements Inc recommends recalibration at intervals no greater than one year Check the appropriate regulations to determine required recalibration intervals Ludlum Measurements offers a full service repair and calibration department We not only repair and calibrate our own instruments but most other manufacturers instruments as well Cali...

Page 24: ...urements Inc Page 6 6 January 2012 Note Never store the instrument over 30 days without removing the batteries Although this instrument will operate at very high ambient temperatures battery seal failure may occur at temperatures as low as 37 C 100 F ...

Page 25: ... Positive pulses from pin 7 of U021 are coupled to the discriminators through R011 and C011 Alpha Beta Discriminator Positive pulses from amplifier U021 are coupled to comparator U012 pin 6 for alpha discrimination and pins 6 and 2 of U011 for beta discrimination R103 alpha threshold provides the reference voltage for alpha comparator U012 R106 beta threshold defined as the lower threshold limit o...

Page 26: ...erence HV SET and alpha beta discriminator controls R201 LO BAT is adjusted so that the meter pointer is aligned with the left vertical mark on the BAT OK or BAT TEST line with 2 2 volt battery input High Voltage Supply High voltage is developed blocking oscillator Q421 T321 C412 and rectified by voltage multiplier CR221 CR224 C221 C223 C211 and C114 High voltage increases as current through Q421 ...

Page 27: ...t rate R407 and R408 provide temperature compensation for changes in the meter resistance due to temperature variations Refer to Processor Board Schematic Drawing 390 107 for the following Power supply Battery voltage is coupled to switching regulator U321 and associated components to provide 5 V to power the μP and display drivers U211 U212 R101 C101 Q101 and Q201 form a delay switch which allows...

Page 28: ...mation is sent from the μP to U211 and 212 via BUS0 3 and ADD0 1 data lines When the SELECT line is brought low by the μP the data is transferred and latched into the drivers until the SELECT line is brought low again The corresponding digits and segments are illuminated corresponding to the stored count information from the μP Audio Alpha and or beta audio pulse frequency is generated by the μP a...

Page 29: ...cables 2 sticky meters 3 battery contacts Note that the first troubleshooting tip is for determining whether the problem is with the electronics or with the detector A Ludlum Model 500 Pulser can be invaluable at this point because of its ability to simultaneously check high voltage input sensitivity or threshold and the electronics for proper counting We hope these tips will prove to be helpful A...

Page 30: ...er is used to check the HV ensure that one with high impedance is used as a standard multimeter could be damaged in this process 2 Check for noise in the detector cable by disconnecting the detector placing the instrument on the lowest range setting and wiggling the cable while observing the meter face for significant changes in readings 3 Check for sticky meter movement Does the reading change wh...

Page 31: ...n is on backwards interfer ence between the speaker and the input preamplifier may cause noise 1 Substitute a known good detector and or cable 2 Has the correct operating voltage been set Refer to the calibration certificate or detector instruction manual for correct operating voltage If the instrument uses multiple detectors confirm that the high voltage is matched to the current detector being u...

Page 32: ...t 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 present ...

Page 33: ...50V 04 5663 C017 10µF 20V 04 5655 C021 10PF 100V 04 5673 C022 100PF 3KV 04 5532 C101 C102 47PF 100V 04 5560 C111 C113 47PF 100V 04 5560 C114 0 0047µF 3KV 04 5547 C121 C122 0 0047µF 3KV 04 5547 C201 C202 10µF 20V 04 5655 C203 330PF 100V 04 5657 C211 0 0047µF 3KV 04 5547 C212 68µF 6 3V 04 5654 C213 1µF 35V 04 5656 C214 0 01µF 50V 04 5664 C221 C223 0 0047µF 3KV 04 5547 C301 68µF 6 3V 04 5654 C311 0 0...

Page 34: ...7 6353 CR211 CR212 BAT54 07 6354 CR221 CR225 GI250 2 07 6266 CR411 MMBD914L 07 6353 R407 03006 165 9 55G100 07 6366 R102 10K BETA THRESH 09 6921 R104 1M BETA WIN 09 6906 R115 1M HV HV READOUT 09 6906 R201 1M ALPHA THRESH 09 6906 R202 200K LO BAT LB 09 6908 R211 1M OVERLOAD 09 6906 R214 1M HV LIMIT 09 6906 R406 5K METER CAL MTR 09 6907 R001 22 1K 1 125mW 12 7843 R002 249K 1 125mW 12 7862 R003 22 1K...

Page 35: ... 249K 1 125mW 12 7862 R121 4 7M 125mW 10 7030 R122 1M 10 7028 R123 1G 12 7686 R212 R213 1M 1 125mW 12 7844 R215 1M 1 125mW 12 7844 R301 2 21K 1 125mW 12 7835 R302 R303 22 1K 1 125mW 12 7843 R311 10 0K 1 125mW 12 7839 R312 22 1K 1 125mW 12 7843 R313 2 21K 1 125mW 12 7835 R314 10 0K 1 125mW 12 7839 R401 200 1 125mW 12 7846 R402 221K 1 125mW 12 7845 R403 7 5K 1 125mW 12 7847 R404 1K 1 125mW 12 7832 R...

Page 36: ...CM7211AMIQH 06 6294 U311 N87C51FA 06 6303 U321 MAX631AESA 06 6285 S301 90HBW06S 08 6710 R101 1M 1 125mW 12 7844 R102 10K 1 125mW 12 7839 R211 2 21K 1 125mW 12 7835 R221 150K 1 125mW 12 7833 R222 100K 1 125mW 12 7834 R301 R306 22 1K 1 125mW 12 7843 RN401 220K 12 7831 L311 150µH 21 9677 T201 AUDIO 4275 083 P3 CONN 1 640456 6 MTA100 13 8134 P4 CONN 640456 2 MTA100 13 8073 P6 CONN 640456 3 MTA100 13 8...

Page 37: ... PHONE JACK TINI 42A 21 9333 S5 7103SYZQE TOGGLE 08 6720 S6 7103SYZQE TOGGLE 08 6720 R1 10K NON LOCKING VOLUME 09 6753 J1 CONN 1 640442 5 MTA100 13 8383 J2 CONN 640442 3 MTA100 13 8135 J3 CONN 1 640442 6 MTA100 13 8187 J4 CONN 640442 2 MTA100 13 8178 J7 CONN 640442 5 MTA100 13 8140 J8 Series C UG706 U 13 7751 J9 CONN 640442 3 MTA100 13 8135 J10 1 8 inch PHONE JACK 18 9080 DS1 UNIMORPH 21 9251 B1 B...

Page 38: ...OUT Drawing 390 105 PROCESSOR BOARD Drawing 390 107 PROCESSOR BOARD LAYOUT Drawing 390 108 CALIBRATION BOARD Drawing 390 112 CALIBRATION BOARD LAYOUT Drawing 390 113 2 sheets DISPLAY BOARD Drawing 390 127 DISPLAY BOARD COMPONENT LAYOUT Drawing 390 128 2 sheets INTERCONNECT BOARD Drawing 390 124 INTERCONNECT BOARD LAYOUT Drawing 390 125 WIRING DIAGRAM Drawing 390 110 Section 11 ...

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