Eberline ESP-1 - Page 51

Voltmeter (20k ohms/volt minimum)
Measure the voltage on TEST connector, pin 11A, (see figure 3-2). Adjust the D
(discriminator) control for a voltmeter reading corresponding to the proper input sensitivity
referenced in Table 1.
WARNING
The high voltage should be set to the "nominal operating
voltage” or less before connecting the detector to the
ESP-1, to prevent damage to the detector. Check the high
voltage by selecting the "HV =" parameter on the
display, Make sure high voltage calibration has been
performed.
Input Vthid*
Sensitivity (volts)
(mV)
0.5 0.071
0.75 0.107
1.0 0.143
2.0 0.286
5.0 0.715
10.0 1.43
15.0 2.15
*Test connector, pin 11A (see figure 3-2).
Table 1. Input Sensitivity vs. "thld
Connect the detector to the ESP-1. With the discriminator properly set, the plateau curve
can be plotted. This is the only data that can truly verify that the detector and instrument
are operating properly and, with the possible exception of G-M detectors, should be plotted
anytime a detector is changed or repaired.
The bias (high voltage) operating point for a G-M detector is fixed by its physical
properties (і.е., size, counting gas, anode size, and fill pressure). Therefore, a check of its
Sensitivity or efficiency may preclude the plateau. It should be within +20 percent of
specified sensitivity at the specified operating voltage (see section VIII).
То plot the plateau (figure 5-1):
(1) Select the "HV=" parameter on the display (inquiry/calibration mode). The second line
of the display shows the current average rate from the detector.
(2) Adjust the НУ control for a low reading from the detector. Record the reading and the
high voltage.
(3)
Increase
HV
in
steps
of
50
volts,
recording
the
high
voltage reading
at
each
step.
Allow
enough time at each step for the reading to stabilize.
(4) Select the operating high voltage and adjust the HV control accordingly.
ESP1.MAN/February 1992