3/18/01 - Just got a Fluke 105B ScopeMeter
E-Bay. This is a portable,
two channel, 100 MHz, digital storage oscilloscope and multimeter.
It came with an optically isolated, RS-232 adapter and Windows 95 software
. I spent the weekend learning how to use it. The following
screen shots show my results so far.
This picture shows the output from a small Variac
I have, set to ~50 volts AC.
This picture shows the drive side of an old,
solid state HV supply that I built in high school (about 25 years ago).
A two transistor oscillator drives the input of a 12 volt ignition coil.
With twelve volts in to the oscillator, the coil primary is receiving
a 30 volt pulse about every millisecond.
Here is the output waveform display from the
ignition coil. This was taken using my 40KV, 1000:1 probe coupled
to the 105B with its normal 10:1 probe. The time between peaks is
~1.75 milliseconds, giving a primary frequency of 570 Hz. There is
also a secondary frequency of ~7 KHz apparent as a ringing after the main
peak. Peak to peak is ~1500 volts. (The input voltage
was lower for this test, I'm still a little nervous about putting KV's
into my new toy.)
This screen shot was made by positioning the
tip of the 40KV probe about a quarter of an inch from the spinning bottle
of my Bill Beaty style electrostatic
motor. You can see the potential swing between ~4 and 10 KV as
the aluminum sectors on the bottle turn past the probe. Since there
are three sectors, the frequency of 26 Hertz corresponds to 520 RPM.
This one is from my other
electrostatic motor. Here the potential is spiking from ~6 to
22 KV as the two points pass the probe tip. The frequency gives the
rotation rate as 498 RPM. (Both motors were connected to ~30 KV.)
Next, I need to get some 50 W
shielded cable so I can hook up my 500KV
probe, and some wire mesh to build a Faraday cage for the 'scope.
10/20/01: I've modified my 500KV probe with
a BNC bulkhead jack so that it can accept 50 W
shielded cable. I bought two 10' and one 1' BNC terminated cables
and two jack to jack connectors so that I can connect them all together.
I also made two heavy ground cables from 6 AWG welding cable and large
copper battery clips. In use, the 1' long cable is connected to the
oscilloscope and the ground clips are conncted to the jack to jack BNC
connector that connects the 1' cable the long cable or cables. I
also bought a BNC to banana jack adapter, so that I can still use the modified
probe with a digital multimeter.