[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Tesla test equipment: high voltage probes



Original poster: "Scott Hanson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <huil888-at-surfside-dot-net>

Regarding the thread on useful test equipment, here are a few comments on
high-voltage probes.
 
Remember that all the small, inexpensive "TV repair" HV probes with a built-in
analog meter are for measuring DC ONLY, and will not help in measuring NST
outputs or AC tank circuit voltages. 
 
Several useful probes for measuring HV AC are made by Fluke and Tektronix, and
can be found as surplus items at reasonable prices:
 
Tektronix P6013  12kV peak   (no dielectric fluid required) good for
measurements at up to 75 MHz
 
Tektronix P5015   original manuals indicate a 40 kV "pulse" capability; good
for measurements up to 75 MHz.
THIS MODEL MUST BE FILLED WITH A FREON DIELECTRIC FLUID FOR SAFE USE. THE
ORIGINAL DIELECTRIC FLUID IS NO LONGER AVAILABLE!!
 
Tektronix P6015A  Current model, does not use Freon dielectric, but is only
listed for 20kV. Big $$$
 
Fluke 80K-40   Listed for 40Kv DC or peak AC (28 kV AC RMS). Not for high
frequency measurements.
 
On the Tektronix units, the special divider resistor is inside a "can" in the
center of the probe. I have seen probes that looked perfect on the outside, but
the resistor was literally vaporized (like it got hit by lightning). I cringe
to think what happened to the test equipment that the probe was attached to .
If you are looking to purchase one of the Tek probes, it might be wise to
inspect the condition of the resistor, and look for any indication of
flash-over. DO NOT touch the resistor itself; any deposit of skin oils, etc on
the surface can lead to tracking and flash-over.
 
In any case very carefully inspect any used HV probes for cracks in the
housing, evidence of surface tracking, evidence of jury-rigged repair, etc.
Remember that under the right conditions high voltage can travel 2-4 times as
far across the surface of an "insulator" as it can through air, so a dirty or
damaged probe housing can create a nice arc path to your hand. The best
practice is to clip the probe to the circuit being measured while it is
unpowered, step back, apply power, and record the measurement data. There's no
need to actually hold the probe while making measurements. 
 
A brief rant: It is my impression from recent postings on this list that some
beginning coilers are in "way over their heads" in playing with pole pigs, etc
and have nearly zero understanding of either Tesla coils or high voltage safety
practices. All it will take are a few  well-publicized "incidents" with
ignorant or irresponsible individuals to put a real crimp in amateur Tesla coil
activities. Everyone on this list needs to help emphasize proper safety
practices, especially to those just starting.
 
Scott