Ludlum Measurements 2241-2 Manual
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Ludlum Measurements 2241-2 Manual

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LUDLUM MODEL 2241-2
SURVEY METER
August 2012
Serial Number 237627 and Succeeding
Serial Numbers

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Summary of Contents for Ludlum Measurements 2241-2

  • Page 1 LUDLUM MODEL 2241-2 SURVEY METER August 2012 Serial Number 237627 and Succeeding Serial Numbers...
  • Page 2 LUDLUM MODEL 2241-2 SURVEY METER August 2012 Serial Number 237627 and Succeeding Serial Numbers LUDLUM MEASUREMENTS, INC. 501 OAK STREET, P.O. BOX 810 SWEETWATER, TEXAS 79556 325-235-5494, FAX: 325-235-4672...

  • Page 4: Table Of Contents

    Switch Board Controls Safety Considerations Environmental Conditions for Normal Use Detector Connector Warning Markings and Symbols Maintenance Recalibration Batteries Technical Theory of Operation Main Board Switch Board Display Board Instrument Setup Entering or Changing Switch Board Parameters August 2012 Ludlum Measurements, Inc.
  • Page 5 8-12 Detector Overload (OVL) Calibration 8-19 Software License Agreement 8-21 Recycling Parts List Model 2241-2 Survey Meter 10-1 Main Circuit Board, Drawing 408 × 223 10-1 Calibration Board, Drawing 408 × 127 10-3 Display Board, Drawing 408 × 259 10-4 Switch Board, Drawing 408 ×...

  • Page 6: Introduction

    Section 1 Section Introduction he Model 2241-2 is a portable microprocessor-based digital scaler/ ratemeter designed for use with scintillation, Geiger-Mueller (GM), and proportional type detectors to measure ionizing radiation. Data is presented on a four-digit (six digits in the scaler mode) Liquid Crystal Display (LCD) with moving decimal point.
  • Page 7 Model 2241-2 Technical Manual Section 1 All of the features described above may be programmed manually using the internal switch board or by computer through the RS-232 port. Two different detector operating parameters may be stored in non-volatile memory. The switch board can be removed after entering or changing parameters to prevent tampering with setup parameters.

  • Page 8: Getting Started

    Check individual item serial numbers and ensure calibration certificates match. The Model 2241-2 serial number is located on the front panel below the battery compartment. Most Ludlum Measurements, Inc. detectors have a label on the base or body of the detector for model and serial number identification.

  • Page 9: Operational Check

    The center post of a “D” size battery is positive. Operational Check Connect a detector to the Model 2241-2 by using the cable provided; firmly pushing the connectors together while twisting clockwise until the connector latches (one quarter-turn). The diagram to the left illustrates how this is done.
  • Page 10 (for fixed response mode) and three times slower when in variable response mode. The slow response position is normally used when the Model 2241-2 is displaying low numbers, which require a more stable display. The fast response position is used at high count levels.

  • Page 11: Specifications

    Model 2241-2 Technical Manual Section 3 Section Specifications : two each, ˝D˝ cell batteries housed in an externally accessible sealed Power Instrument: compartment. Current draw is approximately 35 mA with the backlight Minimum battery voltage is 2.2 ±0.1 Vdc. : Meter readings vary by less than 3% from fully...

  • Page 12: Removable Switchboard Adjustable Parameters

    Model 2241-2 Technical Manual Section 3 : accessible from the front of the instrument (protective Calibration Controls cover provided). These controls are preset at the factory or calibration lab and should not be adjusted by field personnel. : adjustable from 2 to 100 mV;...
  • Page 13 Model 2241-2 Technical Manual Section 3 : selects either 150, 300, 600, 1200, 2400, 4800, 9600, or 19200 bps Baud Rate : adjustable from 0 to 9999 Detector Dead Time Compensation (DTC) microseconds : adjustable from 0.001 to 280 × 10...

  • Page 14: Identification Of Controls And Functions

    Section Identification of Controls and Functions Display The Model 2241-2 utilizes a four-digit liquid crystal display (LCD) with two- digit overflow ( mode) and moving decimal point. The two SCALER smaller digits located in the lower right corner of the display indicate...

  • Page 15: Front-Panel Controls

    Model 2241-2 Technical Manual Section 4 mode when the six-digit display (four digits display and two overflow digits in right corner) reaches 999999 and starts to roll over again. : indicates that the detector is being exposed to radiation OVERLOAD intensities greater than the detector maximum operating limit.

  • Page 16: Front-Panel Calibration Controls

    Model Scaler C Switch OUNT 2241-2 carrying handle, which when depressed, initializes the start of the scaler count accumulation preset scaling time.

  • Page 17: Main Board Controls

    Note: To access the internal circuit boards, unlatch the latches at each end of the Model 2241-2. Carefully separate the top chassis from the bottom cover (referred to as a "can"). The can has the audio speaker (unimorph) with a two-conductor cable attached to the main board.

  • Page 18: Switch Board Controls

    EEPROM, which will retain data even after the Model 2241-2 batteries are removed. After the parameters are entered, the switch board can be removed and the Model 2241-2 will continue to operate from the previously programmed information. Changing parameters and information on switchboard controls are covered in detail in Section 8 of this manual.

  • Page 19: Safety Considerations

    The detector operating voltage (HV) is supplied to the detector by way of the input connector. A mild electric shock may occur if contact is made with the center pin of the input connector. Switch the Model 2241-2 to the position before connecting or disconnecting the cable or detector.
  • Page 20 Model 2241-2 Technical Manual Section 5 The Model 2241-2 Survey Meter is marked with the following symbols: 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. Contact with the subject connector while the instrument is on or shortly after turning off may result in electric shock.

  • Page 21: Maintenance

    The Model 2241-2 instrument may be externally cleaned with a damp cloth (using only water as the wetting agent). Do not immerse the instrument in any liquid.

  • Page 22: Batteries

    Model 2241-2 Technical Manual Section 6 Batteries The batteries should be removed and the battery contacts cleaned of any corrosion at least every three months. If the instrument has been exposed to a very dusty or corrosive atmosphere, more frequent battery servicing should be used.
  • Page 23 Model 2241-2 Technical Manual Section 7 Section Technical Theory of Operation Refer to the Main Board schematic Detector Input/Amplifier for the following: Negative-going detector pulses are coupled from the detector through C021 to amplifier U021. R024 and CR021 protect the input of U021 from inadvertent shorts.
  • Page 24 Model 2241-2 Technical Manual Section 7 High-Voltage Supply High Voltage is developed by blocking oscillator Q241, T141, and C244 and rectified by voltage multiplier CR041-CR043, C041-C043, and C141. High voltage increases as current through R241 increases, with maximum output voltage with Q241 saturated. High voltage is coupled back through R034 to op- amp pin 2 of U131.
  • Page 25 Board schematic for S1 is a 16-position binary rotary switch, which selects the programmable the following: parameters for the Model 2241-2. The switch selects the parameters using the hexadecimal numbering system via buss lines S2-S4 S2-S4 are pushbutton switches that enter/change the variables for each of the 16 parameters.

  • Page 26: Switch Board

    .” This FUNCTION Switch switch selects a parameter setup mode for the Model 2241-2. If the board is not installed, the normal operation mode (counting mode) is selected. If the switch board is installed, the selector switch must be set to the 0 position for normal instrument operation.
  • Page 27 Model 2241-2 in the normal POSITION 0 NORMAL OPERATION (counting) operating mode. Unplugging the switch board from the Model 2241-2 main board defaults to the normal operating mode. (µs) allows changing the detector dead time POSITION 1 DEAD TIME correction for the current detector setup.
  • Page 28 POSITION 3 DISPLAY UNITS detector setup number. The Model 2241-2 and detector may be calibrated in either exposure rate (R/hr or Sv/h) by entering the appropriate Calibration Constant (position 2) and Dead Time correction (position 1). The Model 2241-2 will automatically convert to the correct reading when switching between R and Sv.
  • Page 29 POSITION 6 RESPONSE TIME the current detector setup. If the response is set to 0, the Model 2241-2 automatically calculates (for variable mode) the time constant based on the incoming cps. If a variable of 1-199 is entered for TC, the response time becomes fixed.
  • Page 30 POSITION D DATA DUMP MODE ratemeter data every two seconds. The Model 2241-2 is fully functional during RS-232 data dump with the exception of the audio function. The LCD will alternate between display of the ratemeter and the word “...

  • Page 31: Loading Default Parameters

    Ludlum Measurements, Inc. offers a PC compatible software program that incorporates the read/write commands necessary to communicate between the PC and the Model 2241-2. The program also incorporates an algorithm to calculate the detector Calibration Constant and Dead Time Constant. The software is offered in a DOS version (part number 1370-025) or a WINDOWS version (part number 1370-024).

  • Page 32: Calibration

    Baud Rate 9600 LCD Time Off 5 seconds Detector Calibration The Model 2241-2 calibration routine consists of entering detector parameters into memory by way of the switch board and adjusting the controls ( ) for the specific detector operating DISC requirements.

  • Page 33: General Detector Setup Information

    Model 2241-2 Technical Manual Section 8 The last subsection of calibration deals with the Detector Overload ( ENERAL ETECTOR ETUP NFORMATION The operating point for the instrument and probes is established by setting the probe voltage and instrument sensitivity ( ).

  • Page 34: Counts Per Minute (C/M) Calibration

    OUNTS PER MINUTE ALIBRATION This procedure will setup the Model 2241-2 for the counts per minute (C/m) mode of operation. Refer to Section 8, (Page 8-2 and following) for more information on setup parameter variables.
  • Page 35 Connect the Model 500 Pulser to detector input and adjust DISC the specific detector operating parameters. Adjust the pulser amplitude to 1.5 times the Model 2241-2  discrimination level. Adjust the pulser output to 800 cpm and confirm that the Model ...

  • Page 36: R/Hr Calibration

    Model 2241-2 Technical Manual Section 8 Confirm that the scaler readout is within 2% of the pulser input rate.  Ensure that the s function by inputting the preset  ALERT ALARM alarm levels as to initiate the alert and alarm conditions.
  • Page 37 PC and the Model 2241-2. The program also incorporates the algorithm to calculate the detector CC and DTC. The software is offered in a DOS version (part number 1370-025) or a WINDOWS version (part number 1370-024).
  • Page 38 Model 2241-2 Technical Manual Section 8 Preliminary CPS Setup Refer to Section 8, subsection, “Function Switch Position Descriptions and Variables” for cps readout variables. Select position 1 on the toggle switch located on the front panel. Starting with switch position 1, enter the following variables: FUNCTION SWITCH POS.
  • Page 39 Model 2241-2 Technical Manual Section 8 Reference the table at the end of this section to determine the cps/exposure rate (cps/ER). The conversion can be determined by placing the detector in a radiation field, which produces from 50 to 200 cps. Calculate the count/exposure = cps / ER rate using the equation to the left.
  • Page 40 Model 2241-2 Technical Manual Section 8 CC and DTC Algorithm Equations (5) and (6) convert units per time (R/hr Display Units) to units per second: uni t s uni t s ⇒ second t i m e Insert the cps lo data point (8 mR/hr for the Model 44-9 example)
  • Page 41 Model 2241-2 Technical Manual Section 8 As an example, assume a 60-second count sample in a low field of 8 mR/hr: Example 26,427 CORR Place detector in the high field and enter the counts per second: Equation 8 counts SAMPL...
  • Page 42 Model 2241-2 Technical Manual Section 8 Enter the results of equations (9) and (10) into equation (11) to solve for Equation 11 count Example − − − Solve for f Equation 12 units CORR Example − − − − 2.22 (2.22...
  • Page 43 This table represents some of the common detectors operated with the Model 2241-2. Consult the LMI sales department for information concerning detectors not listed in the table above. *The dead time values for these scintillation detectors are due to the dead time of the Model 2241-2 electronics.

  • Page 44: Detector Overload (Ovl) Calibration

    OVERLOAD accordingly. Example: Ludlum Model 44-9 is calibrated with Model 2241-2 in the R/hr units display, utilizing DT. The upper linear operating point is 400 mR/hr for the Model 44-9. Place the detector at the 1000 mR/hr point and adjust the control to initiate the alarm.
  • Page 45 Model 2241-2 Technical Manual Section 8 The detector overload or saturation point for alpha and/or beta scintillation detectors is when the detector face (Mylar) has been punctured, allowing light to saturate the photomultiplier tube (PMT). The pulse output will decrease or even appear non-responsive to any radiation activity, depending upon the size of the puncture and the light intensity to the PMT.
  • Page 46 Model 2241-2 Technical Manual Section 8 Ludlum Measurements, Inc. Page 8-21 August 2012...
  • Page 47 Model 2241-2 Technical Manual Section 8 Page 8-22 August 2012 Ludlum Measurements, Inc.
  • Page 48 Model 2241-2 Technical Manual Section 8 Page 8-23 August 2012 Ludlum Measurements, Inc.

  • Page 49: Recycling

    To this end, Ludlum Measurements, Inc. strives to supply the consumer of its goods with information regarding reuse and recycling of the many different types of materials used in its products. With many different agencies –...

  • Page 50: Parts List

    Technical Manual Section 10 Section Parts List Reference Description Part Number Model 2241-2 Survey Meter UNIT Completely Assembled Model 2241-2 Survey Meter 48-2731 BOARD Completely Assembled Main Circuit Board, Drawing 408 × 223 Main Circuit Board 5408-223 CAPACITORS 0.1µF, 50V 04-5663 0.1µF, 50V...
  • Page 51 Model 2241-2 Technical Manual Section 10 Reference Description Part Number C241 1µF, 35V 04-5656 C242 68µF, 10V 04-5654 C243 0.1µF, 50V 04-5663 C251 68µF, 10V 04-5654 TRANSISTORS Q101 2N7002L 05-5840 Q141 MMBT3904LT1 05-5841 Q211 2N7002L 05-5840 Q212 MMBT4403LT1 05-5842 Q241...
  • Page 52 Model 2241-2 Technical Manual Section 10 Reference Description Part Number R023 10K, 1/4W, 1% 12-7839 R024-R025 4.75K, 1/4W, 1% 12-7858 R026 8.25K, 1/8W, 1% 12-7838 R031 4.7M, 1/4W, 5% 10-7030 R032 1M, 1/4W, 5% 10-7028 R033-R034 1G, FHV-1, 2% 12-7686 R111-R113 22.1K, 1/4W, 1%...
  • Page 53 Model 2241-2 Technical Manual Section 10 Reference Description Part Number R112 1M, OVERLOAD 09-6814 R113 100K, DISC 2 09-6813 R114 100K, DISC 1 09-6813 RESISTORS R115 1M, 1/3W 12-7751 R116 1K, 1/3W 12-7750 R118 10K, 1/3W 12-7748 R119 1M, 1/3W...
  • Page 54 Model 2241-2 Technical Manual Section 10 Reference Description Part Number Switch Board, BOARD Completely Assembled Drawing 408 × 45 Switch Board 5408-052 CAPACITORS C1-C2 4.7µF, 10V 04-5578 C3-C4 10µF, 20V 04-5592 4.7µF, 10V 04-5578 100µF, 10V 04-5576 INTEGRATED MAX220EPE 06-6359...
  • Page 55 2363-191 Casting 7408-181 Front Panel Lexan 7408-208 Battery Lid Lexan 7408-209 Label Model 3 Cal Cover 2310602 Model 2241-2 Flat Handle Assy. 4408-179 Clip Probe with Screws 7010-008-01 2 ea Can Gasket 22-9773 Portable Knob 08-6613 Portable Battery Gasket 7363-183...

  • Page 56: Main Circuit Board, Drawing 408 × 223

    Model 2241-2 Technical Manual Section 11 Section Drawings Optional Source Holder Assembly, Drawings 62 × 166 & 62 × 166B Main Circuit Board, Drawings 408 × 223 (3 sheets) Main Circuit Board Component Layout, Drawing 408 × 224 Calibration Board, Drawing 408 × 127 Calibration Board Component Layout, Drawings 408 ×...

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