Testatika Pots as Capacitors (Mk1) Testing

The objective of this experiment was to test the theory that the testatika pots are really capacitors and if a DC voltage could be gotten from them. One result, as is detailed below, is that there was a DC voltage but only because of leakage current at one electrode. When the leakage current was fixed, the DC voltage disappeared. The output power was around 21milliwatts. Could the testatika's pots be leaky capacitors? Another perhaps more useful finding was that the small 2V peak-to-peak AC that was riding on the DC HV input was amplified about 16 times to around 32V AC on output. It's uncertain yet if the amplification was also driven by some leakage current.

The Capacitors

Each capacitor consists of 2 electrodes (an inner one and an outer one) plus a center grid. Following in the picture below from left to right is: the inner electrode consisting of 10 AWG insulated wire formed into a coil, the center grid for getting output, and the outer electrode which is also a grid. The grids are aluminum. The inner electrode slides into the biege PVC cylinder which has the center grid wrapped around it. This in turn slides into the black ABS cylinder which has the outer electrode wrapped around it. Once assembled you have the completed capacitor as shown on the right of the equal sign.

The two capacitors connected together by the wires that will be connected to the HV side. Note that for the one on the left that is the center electrode and for the one on the right that is the outer electrode (the redish/orangish wire coming from the inner electrode of the capacitor on the right is not connected to these, its end is just sitting close by).

The Experiment Setup

(1) ABS (plastic) poles for attaching things, (2) 24V supply for HV 30kV supply (hidden, see next picture), (3) HV probe for measuring input voltage (see next picture for more), (4) oscilloscope for displaying input voltage and output voltage, (5) meter for measuring input current (caused by leakage), (6) meter for measuring output current, (7) and (8) capacitors.	(1) HV 30kV power supply (gets input from 24V supply), (2) HV probe tip touching output of HV 30kV supply, (3) meter for measuring input current (caused by leakage), (4) HV input connections to capacitors, notice they are different for each capacitor (more in next two pictures), (5) HV three wire connection covered in wax to minimize leakage.
(1) HV goes to outer electrode, (2) connection to center grid for output, (3) ground goes to center electrode.	(1) HV goes to center electrode, (2) connection to center grid for output, (3) ground goes to outer electrode

The Results

The tests were done by simply turning up the high voltage while writing down current readings and snapping pictures of the oscilloscope output. The following are the results summarized and below that are the oscilloscope pictures.

The DC component

One interesting thing that was found was that there was a large DC voltage measured across the center grids. As the high voltage was turned up, the input current increased though the measured input voltage stayed fairly flat. This makes sense as the leakage would hamper the voltage from rising. The input current was due to leakage at one capacitor between the connection to the center grid and the top edge of the outer grid (details below). The leakage is what resulted in the DC output and is what kept the measured input voltage down.

The AC component

The other interesting thing that was found was that there was a large AC amplified component riding on the DC one. The AC on output was due to ripple in the input voltage, known to be the case because they had the same frequency. The AC ripple on input was only about 2 volts peak-to-peak. The AC voltage on output was as much as 160 volts. However, when the leakage current was eliminated (as much as it could be) the AC voltage on output was only 32 volts (see very bottom). It's possible that this was due to there still being some leakage current. More experimenting is needed as the significance of this AC component was not thought about until a few weeks after the tests.

The Data

The following shows where the leakage was coming from. This resulted in the input current. This input current is what held this center grid at a different voltage than the center grid in the other capacitor and is why an output DC voltage was measured.

I fixed the above leakage by putting corona dope on the wire coming from the center grid as is shown in the following picture.

The result was that I could now turn the high voltage much higher without any output DC at all. This means that there was no longer a potential between the center grids except for the AC component. Note that the AC component is less but still present, possibly due to there still being some small leakage current. The following oscilloscope picture shows this.