Tera Ohm Meter - Power Supply
The parts list which is not in the circuit is listed below, the circuit is 15 years old so you may have problems getting the parts, but you may get some idea on high resistance measurement.| IC1 | ICL7107 | A/D converter 31/2 | intersil maxim |
| IC2 | ICL7650 | chopper stabilized amplifier | intersil maxim analog |
| IC3 | CA3140 | any opamp | Texas Instruments |
| IC7 IC9 | NE555 | timer | National Semiconductor |
| IC8 | LM723 | regulator | National Semiconductor |
the above list is from my memory, hence it may be wrong, i have forgotten this circuit, this circuit was scanned by a hp photosmart and resized and optimized by irfanview. also note the technology may be obsolete, but basic idea is still the same today.
with these circuits you can make an insulation tester going upto one tera ohm (2 Tera ohm max). hence currents will be in pico amps, great care required in design. Also 1000 Volts DC is generated which can cause injury. take great care. the above circuit is for the advanced instrumentation hobbyist only, do not try it at home.
