High Resistance Meter

Advertise in delabs

I don’t remember if this circuit worked properly. But a few were made and i might not have shown the modifications that were done to make it work. This was meant to be a portable, low cost, insulation tester for an electrician. If you try it out and debug it it may work well.

High Resistance Insulation Materials

A negative voltage is derived by shifting gnd with two diodes, i feel this did not work very well. Two pins of CD4028 pins are also used to boost the reference to get two extra ranges as 4051 has a 100E on resistance.

High Resistance Meter

The 555 clock makes 4029 counter count. But the clock can be clamped to gnd by a TL062 window comparator. The clock is frozen when the input value to comparator pin 5-2 is within a lower limit and upper limit “window” pin 3-6.

Insulation Tester

The 4029 counter BCD is decoded to decimal by 4028 which drives the LEDs, keep LED drive within 3mA or chip will be loaded. Use high efficiency extra-bright LEDs.

The 4029 BCD also controls a shunt resistor array with CMOS switches 4051. The voltage across shunt is a sample of leakage current. This is compared in the window comparator to freeze the Clock and LED display to give a reading of the leakage current or Insulation Resistance.

More delabs Schematic Diagrams

  • 5V -1A Power Supply using LM25755V -1A Power Supply using LM2575
    A Power Transistor which is having a drop of 4 Volts across it and passing 3 amps thru it, may dissipate around 12 Watts of [...]
  • Mains Voltage monitor using LM3914Mains Voltage monitor using LM3914
    This Circuit helps in the monitoring of mains supply voltage. It does not use a isolation step down transformer. This has to be constructed only [...]
  • Thermocouple Amplifier StandardThermocouple Amplifier Standard
    Thermocouple is the most common sensor in Industrial Temperature Measurement. The Signal Conditioning involves Cold Junction Compensation and High Gain DC Amplification. The output of [...]
  • Relay Driver – ElectromagneticRelay Driver – Electromagnetic
    This circuit is a standard way of driving Small Power Relays from Control Signals generated by Logic or Opamp Circuits. C2 and R5 form a [...]
  • Pulse width modulation using 555Pulse width modulation using 555
    IC1 astable gives a fixed square wave at pin 3, C1 and R1 derive uS trigger pulses from IC1 and this will trigger IC2 monostable [...]
  • Crystal Oscillator – Parallel ResonantCrystal Oscillator – Parallel Resonant
    74HCU04 is a chip that was made for this purpose, HCT may not work for such a circuit. C1 and C2 can go to upto [...]
  • Connection Diagram of AC Control SSRConnection Diagram of AC Control SSR
    SSR or Solid State Relay or Electronic Relay Connection Method. This is a Thyristor Based Normally Open 230V Switch that can be turned on / [...]
  • Three Opamp Differential InstrumentationThree Opamp Differential Instrumentation
    This is the best Instrumentation OpAmp, Great CMRR, ensure supply has no ripple and keep analog and digital grounds separate. Ri can be replaced with [...]
About delabs 152 Articles
Product Design - Industrial Automation and Instrumentation. -

Be the first to comment

Leave a Reply