Insulation Tester HP-6688B

An insulation tester for under 50 CHF. Let's see if it's any good.

Wow, you really get a lot for your money. It's quite large.
Display with backlight turned on.
Connection sockets. For insulation measurement, I will only need E and L.
Back side.
Battery compartment. It requires 6 AA batteries.
Datasheet measurement ranges.
Datasheet types.
Advertisement: size.
View inside.
Transformer for high voltage generation: yellow.
Voltage multiplier on the left with blue capacitors.
Wires to the 4mm sockets.
MELF resistors.
1.2 MOhm resistor. Presumably for operator protection. At 5000V, a maximum of about 4 mA flows through it, which is not lethal.
R61 27 kOhm.
I am trying to reconstruct part of the circuit. Schematic.
I still have some resistors lying around and will measure them. Test resistor 10 MOhm.
Test resistor 100 MOhm.
Test resistor 1 GOhm.
Test resistor 10 GOhm.
Test resistor 100 GOhm.
Measurement results. The measured values match the nominal values surprisingly well. The voltage measured with a Tektronix TX3 also fits well. The resistors are not precision resistors and I have not measured them independently. With this voltmeter, I can only measure up to 1000V. Due to voltage ratings, I cannot measure all resistors in all voltage ranges.
For this price range: I am impressed.
		Last Change: 2026-05-19 Zulu v4.0.3