PCM-2 Manual.pdf - Voss Associates

Long probes
Medium probes ­
Small probes
1 hour
45 min
30 min
b) For incomplete (unfaced) probes, apply the probe's silicone gasket
to its oLiler edge, seating and smoothing it dovvn all around. Turn the
gasketed probe open face down on and clamped to the metal plate (vvhich
has been wiped clean of any dirt or dust) and connect up the vacuum pump
hose to one of the probe's gas finings. Connect the vacuum gage and a
small length of tubing wlfitting plug to the other gas fining on the probe.
Operate the pump until a vacuum of approx. 14 in. Hg is achieved (appro:\..
15 sec.) Quickly disconnect the vacuum hose from and connect the P-I 0
gas supply to the probe then turn off the pump. When the vacuum gage
falls off to a zero reading, quickly disconnect the gage from the probe and
replace it with an exhausting hose. It is important to connect this exhaust
line to restore probe chamber gas pressure to ambient since an over
pressured probe may also cause erroneously successful arc test results.
This is the quick method of purging PCM-2 detectors.
Arc test each channel of the detector by first connecting the high-poner's
"hot" lead to that channel's banana plug and its ground lead to both the
probe's grounding (MOB) stud and the metal plate.
3. Adjust the high voltage sening on the high-poner to 1750 volts. Switc11
on the high-potter and. while listening for audible arcing (spark) noises.
monitor the high-poner's current meter for both leakage current and any
arc "spikes". Apply power to the probe channel for I minute. Only one
audible arc event, capable of causing a current meter spike, is acceptable
in this one minute test period. Discount small audible arcs that do not
move the current meter. Acceptable leakage currents for the probes are:
Large
Medium
Small
160-190 micro amps
200-240 micro amps
100-130 micro amps
NOTE:
Some arcing can result during initial testing due to the presence of Iint or
dust in the probe chamber causing an arc path. This situation is usually
self correcting in that these particle contaminates tend to burn out in only
a few seconds duration of high voltage arcing. Tests which evidence initial
arcing should. for this reason, be repeated to verify that the probe is truly
arcing. Leakage current values which result below these noted acceptable
ranges for the detectors are often indicative of low P-IO counting gas flow
rates and/or an improperly installed high voltage connection.
4. Switch off the high-pot tester and record the detector channel's leakage
current on a labeling sticker on the back of the probe cl1amber in that
section of the probe.
l0429-i\S2S/PCM