Model 4612 Twelve-Channel Counter
Technical Manual
Section 7
Ludlum Measurements, Inc.
Page 50
November 2019
Hardware Calibration
A Ludlum Model 500 Pulser or equivalent is required. If the pulser does not
have a high-voltage readout, use a high impedance voltmeter with at least
1000 megohm input resistance to measure the detector voltage. Remove the
cover of the Model 4612.
1.
Connect the Model 500 Pulser to the Model 4612 Channel #1,
using an appropriate cable.
2.
Adjust the pulser for 40,000 cpm and set the pulse amplitude to
-10 mV (negative amplitude).
3.
Start the Counter.exe program and “connect” to the Model 4612.
4.
Observe the Model 500 HV readout (or connect the high-
impedance meter). Using your PC and the Model 4612 Counter
software, set the HV control to 900 Vdc. Check for an actual high
voltage reading of 900 V ±4 V and adjust, if necessary, the
potentiometer on top of the slave board (#1) and closest to front
panel for a reading of 900 Vdc on the voltmeter or pulser.
Connect the voltmeter between the HVR test point (+) on the rear
panel of Slave #1 and ground (the screw head (-) located just to
the right of the LMI logo on the panel). Adjust the HVR pot
located closest to the rear panel for a meter reading of 0.900 Vdc
±0.004 Vdc.
5.
Set the HV to 500 and finally to 1200 Vdc and confirm that the
reading of the HV meter corresponds to the external voltmeter
within
5% of each reading.
6.
Set the LLD for all channels to 100 and set the ULD to 200.
Note: This results in a calibration level of 10 mV threshold and
10 mV window.
Section
7
Summary of Contents for 4612
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