LUDLUM 500-2 User manual
LUDLUM MODEL 500-2
PULSER
September 2015
Serial Number 206262 and Succeeding
Serial Numbers
LUDLUM MODEL 500-2
PULSER
September 2015
Serial Number 206262 and Succeeding
Serial Numbers
STATEMENT OF WARRANTY
Ludlum Measurements, Inc. warrants the products covered in this manual to be free of
defects due to workmanship, material, and design for a period of twelve months from the
date of delivery. The calibration of a product is warranted to be within its specified
accuracy limits at the time of shipment. In the event of instrument failure, notify Ludlum
Measurements to determine if repair, recalibration, or replacement is required.
This warranty excludes the replacement of photomultiplier tubes, G-M and proportional
tubes, and scintillation crystals which are broken due to excessive physical abuse or used
for purposes other than intended.
There are no warranties, express or implied, including 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 damages, arising from the purchase, use, or inability to use
product.
RETURN OF GOODS TO MANUFACTURER
If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please send to
the address below. All shipments should include documentation containing return shipping address,
customer name, telephone number, description of service requested, and all other necessary information.
Your cooperation will expedite the return of your equipment.
LUDLUM MEASUREMENTS, INC.
ATTN: REPAIR DEPARTMENT
501 OAK STREET
SWEETWATER, TX 79556
800-622-0828 325-235-5494
FAX 325-235-4672
Ludlum Measurements, Inc. September 2015
Table of Contents
Introduction 1
Specifications and Controls 2
Power 2-1
Pulse Output 2-1
High Voltage Readout 2-1
Pulse Rate 2-1
Pulse Amplitude 2-1
Pulse Polarity 2-1
Accessories 2-2
Getting Started 3
Measuring Instrument High Voltage 3-2
Determining Pulse Height Threshold 3-2
Electronic Count Rate Calibration 3-3
Determining Dose Rate Conversion 3-4
“Bottom Range” Calibration 3-4
Safety Considerations 4
Environmental Conditions for Normal Use 4-1
Cleaning Instructions and Precautions 4-1
Warning Markings and Symbols 4-2
Replacement of Main Fuse 4-3
Maintenance and Recalibration 5
Maintenance 5-1
Recalibration 5-1
Recycling 6
Parts List 7
Model 500-2 Pulser 7-1
Pulser Board, Drawing 208 X 61 7-1
Readout Board, Drawing 208 X 176 7-3
HV Readout Board, Drawing 208 X 145 7-4
Ludlum Measurements, Inc. September 2015
Readout Controller, Drawing 208 x 173 7-4
Amplitude Readout Board, Drawing 208 x 17 7-5
Wiring Diagram, Drawing 208 X 181 7-5
Drawings and Diagrams 8
Model500-2Pulser TechnicalManual Section1
Ludlum Measurements, Inc. Page 1-1 September 2015
Introduction
he Ludlum Model 500-2 Pulse Generator (Pulser) provides the
functions necessary for use in calibrating Ludlum instruments, as
well as many other scaler/ratemeter instruments. The adjustable
output pulse rate is displayed on a three-digit LED readout.
Potentiometers (both coarse and fine controls) and a multiplier switch
provide rates from 10 to 9.9 x 106counts per minute (cpm). Pulse amplitude
is controlled by a multiplier switch and a LO/HI potentiometer, while pulse
polarity is chosen by a selector switch. Amplitude may be varied between 0
±5 volts; displayed on a four-digit LED readout. The high voltage of the
instrument under test is displayed on a four-digit LED readout.
Model 500-2 Pulser
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Specifications and Controls
0
Power: 95-135 Vac, 50/60 Hz at less than 20 volt-amperes
Pulse Output: standard connector “C” type (“C” cable is provided)
High Voltage Readout: measured by a high-impedance voltmeter up to
1999 volts on the PULSE OUT connector. Voltmeter impedance is
1000 megohms ±10%. Voltmeter linearity is ±5% of the reading.
Pulse Rate: six multiplying ranges provide pulse rate settings of X0.1
through X10K, displayed on a three-digit LED readout. Minimum pulse
rate is 1 cpm, while the maximum pulse rate is 9,900,000 cpm, with
accuracy better than ±2% of the reading.
Pulse Amplitude: read on a four-digit LED readout. Four scales are
provided: 0-5 millivolts, 0-50 millivolts, 0-500 millivolts and 0-5volts.
The desired range is selected using the four position switch. Actual pulse
amplitude is within 10% of the reading.
Note
If the Pulse Rate is above 500 cpm with the range multiplier
switch set to X10K, a slight decrease in overall pulse amplitude
may occur.
Pulse Polarity: The output pulse polarity may be selected by a switch
located on the front panel. Total pulse width is typically 7.0
microseconds, comprised of a leading edge of 0.3 microseconds, a pulse
flat top of 1.7 microseconds and a pulse trailing edge of 5 microseconds.
The positive pulse width is less than 2.25 microseconds.
.
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Accessories: Series “C” to “BNC” and “C” to “MHV” adapters are
provided.
Note
If the pulse amplitude from the Pulser exceeds ten times the
input sensitivity of the test instrument, double pulsing may
occur in the instrument under test.
Model500-2 Pulser Technical Manual Section3
Ludlum Measurements, Inc. Page 3-1 September 2015
Getting Started
he Ludlum Model 500-2 Pulser (Pulser) is commonly used to
calibrate a variety of radiation detection (survey) equipment to a
certain count rate (CPS-counts per second, CPM-counts per
minute, KCPM-kilo counts per minute, etc.). This is accomplished
by measuring high voltage, determining pulse height threshold, and feeding
simulated pulses to an instrument. The basic methods associated with
calibrating such equipment will be covered in this section, giving the first
time user some valuable principles to build upon as he/she becomes more
proficient in the task of electronic calibration.
Before calibrating any piece of survey equipment, some information about
that piece of equipment would be of much value and can often found in
respective instrument manuals:
1. You should know the polarity of the detector to be used with
the instrument. Most radiation detection instruments used with
GM (Geiger Muller), proportional, or scintillation detectors
produce a negative pulse.
2. You must know the type of detector used with that particular
instrument. This is important because the Pulser actually
emulates the detector.
3. It is helpful to know the voltage requirements of the detector
that will be used with the instrument (often 900 Vdc is required
for GM detectors). High voltage requirements for scintillation
detectors are determined by the detectors’ plateau.
4. Does the instrument you want to calibrate utilize an
intermediate preamp or “smart” electronics at the detector? Be
aware that the pulser cannot simulate a detector in these cases.
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If you are calibrating an instrument with an analog display, you will first want
to ensure that the meter movement has proper mechanical zero.
Adjustments are typically on the front of the meter bezel and must be
made with the instrument power OFF and the instrument in its normal
handheld (or “resting”) position.
Measuring Instrument High Voltage
Use a detector cable of identical length of that which is used in normal
operation of the instrument to connect the instrument to the pulser. Turn
the pulser power switch to the ON position.
Ensure that the instrument power is ON and then adjust the high-voltage
output (consult instrument manual) for a proper high-voltage reading on the
pulser high voltage meter face. Remember, high-voltage requirements are
based on the detector that will be used with the instrument.
Determining Pulse Height Threshold
On the pulser, adjust the AMPLITUDE, and –NEG/+POS Pulse Polarity
to that which is specified in the particular instruments’ instruction manual
(and/or plateau graph) and calibrate if necessary/applicable.
If an instrument manual is not available, the following procedure can be
used to determine pulse height threshold.
With the instrument being calibrated set to the highest range, adjust the
pulser count rate until the meter reads full scale. Then, adjust the pulser
AMPLITUDE down until a 25% loss of counts is read on the meter face.
Record the pulse height threshold from the pulser amplitude readout/meter.
Test above and below the threshold by adjusting the pulser AMPLITUDE
while observing a rapid increase or decrease (corresponding to increase or
decrease in amplitude) in meter counts.
The pulser can also be used to set the pulse height threshold on instruments
with an adjustable threshold. The procedure is basically the same as the
preceding procedure. If the desired threshold has not been achieved, adjust
the threshold control and repeat this procedure until the desired results are
met.
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