[Boatanchors] Looking for Documentation on IM-5210 HV Probe

[Barry L. Ornitz]

Bob Bethman asked about a Heath high-voltage probe:

>     This week's latest Hamfest find is a Heathkit IM-5210 High
Voltage
> Probe.  I am looking for a copy of the manual.  A PDF or any other
form of
> scan would be just fine.

I have a Heath high voltage probe but I am not sure if it is the same
model number.
Like most HV probes, it is red and about a foot long with lots of
insulation around the handle.

Inside there is a 1090 Megohm resistor.  The resistor is spring loaded
to contact the tip, and the bottom of the resistor is held in by
screwing on the connector which has the cable.  This is an old-style
Amphenol shielded microphone connector.

The probe is designed to work with an 11 Megohm VTVM.  These meters
have an internal impedance of 10 Megohms and have an additional 1 Meg
resistor in their probe.  The meter is calibrated to handle the 10/11
voltage reduction.

When the HV probe is added, the combined resistance of the meter and
probe is 1100 Megohms.  Thus the probe provides a 100X reduction in
input voltage to the meter.  The overall insulation and such provides
typically 30,000 volts on the meter's 300 volt scale.  If your plastic
probe has been stored properly (few have) you might be able to push
the voltage up to 50,000 volts.  However, if the plastic is scratched
or dirty, this will not be possible.  Cleaning the outside plastic
with soap and water, followed by buffing with Brasso, followed by
another soap and water cleaning may help here.  Dry thoroughly! That
surface dirt becomes quite conductive at high voltages.  If the inside
of the probe has ever gotten wet, you should probably throw the unit
in the trash for being too dangerous to use.

Remember these probes are only good for DC.  Think of the probe and
meter capacitance as an RC low-pass filter.  With that much
resistance, it does not take much capacitance to cut off even low
frequencies.

Probes designed for modern digital meters will have different resistor
values.  These meters generally have a 1 Meg input resistance on all
scales over 200 mV.  Here the probe resistance would be 99 Megs.
However some digital meters have an internal resistance of 10 Megs and
the high voltage probe would be 990 Megohms.

        73,  Dr. Barry L. Ornitz     WA4VZQ     ornitz@tricon.net