Insulation Tester power supply - del50001
This is a Inverter Power supply that generates a
Precision High voltage of 100V to 1000V. The voltage
is low ripple and High Regulation and extremely
Reverse Bias Leakage Tester
One of the earliest Instruments i designed, built
and sold in the 80s. A Digital Insulation tester
that helps evaluate polarization index in
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.
The parts list which is not in the circuit is listed
below, the circuit is many years old. but you may
get some idea on high resistance measurement.
Oscillator Circuit Design
The parts list is from my memory, hence it may be
wrong, i have forgotten this circuit, also note the
technology may be obsolete, but basic idea is still
the same today.
Theory of Operation.
IC7 555 as an Astable chops the DC with T2 NPN
transistor. TR2 was a Russian U Core High-Freq
Transformer. The secondary was insulated with mylar,
layer to layer and impregnated in Mica-Lacquer or
varnish. The 723 Chip along with T1 is The
closed loop regulator which changes the DC which is
This is part of an old product of mine, it is a
megger, a tera ohm meter or call it an insulation
tester. IC8 is LM723 - Voltage
Voltage to Current Convertor using LM723
The LM723 works like a closed loop Regulator but its
DC output from T1 is chopped by a 555 and T2.
This is stepped up by a small transformer (Russian U
Core, with layer to layer insulation) as it has to
meet with near 2KV spikes at output at times.
Two diodes are used as 1K is the limit of 1N4007. A
switching diode like FR105 may be better. The
caps are piled up due to the high voltage. The
feedback is an attenuated sample of HV output thru
the R8 4.7M.
The high voltage current is low for safety reasons,
but great caution has to be taken. TR1 must be
a 1 A, 10-0-10 V Transformer.
The high voltage is attenuated and that is the
feedback to 723 chip which by comparing to a
reference, controls the output. The diodes and caps
are in series to withstand 1000V and above.