[Test-Equipment] (no subject)

[smattila at homemail.com.au]

Chris,

The meter is unknown to me, but usual DC probes for
high-ohm (more than 1 Mo) input meters contain only
non-inductive resistor, about 1 - 20 ko. Best to use
a SMD resistor. Low-ohm meter probes do no contain
anything, just a wire. If it is RF probe, there is
a 1 - 10 nF 400 V ceramic capacitor from the tip to
input and a diode like 1N4148 (silicon) or OA90 (germanium)
from input to ground. These are good between 0.5 - 60 Vpp RF.
Older meter have a vacum tube/valve like EA50 or EA63
instead of the semiconductor diode. You can use low-power
schottky diode, too. It get you more accurate readings
below 1 volt.

If you can not find exact replacement for the schottky
diodes, try similar-looking, ie. a small with 75 V 100 mA
rating or a large diode with as high voltage and
current ratings you find. Knowing the actual voltages and
currents helps, of course. Schottkys have different
swiching speeds, etc., but this usually work. Schottkys
are also reasonable replacements for germanium diodes, but
not tunnel diodes. Remember, the voltage limit for schottkys
is quite low, all high-voltage diodes are ordinary
silicon ones. Rocky in Melbourne (Victoria, Australia)
has got pretty good stock of these components at reasonable
prices.

Commenting about unusual test equipment is easier, if you
explain what it is and is it semiconductor or tube/valve type
thing.

-- 
Sakari Mattila, VK2XIN
+61 408 533474
smattila at ieee.org
--