Current Amp digital control – DMM Project

R6 is the Shunt thru which the current to be measured passes. F1 fuse is to protect shunt. D1-D4 ensures that the current flow is not broken if the shunt blows. The Ammeter is always used in series in a circuit.

OP07 is used here as a digitally controlled amplifier as the voltage offset error is around 75uV. 4052’s digital controls A-B set the range by selecting R1, R2, R3, R5 for the digital code at A-B. The inverting amplifier changes the gain and four current ranges are got. The output of this circuit has to go to a buffer and cannot be loaded directly. R8 is offset trim at very high gains, it has to be adjusted for a zero output of opamp for zero current measured.

Current Amp digital control - DMM Project

Rf and Ri are 0.1% MFR, if costly, use bourns 10T trimpot or a difficult way – use series parallel combination and scratch 10% part of resistor network to increase value.

Read more at my – Current Shunt Amplifier with digital control – del20014

  • Precision Attenuator for Digital uC Control
    When Instruments are designed a analog front end is essential and also as most equipment have digital or microcontroller interface the analog circuit needs to [...]
  • Constant Current Source LED Drive
    This is a Constant Current Source LED Driver, When the LED driver Upper-NPN is driven by a voltage thru 4.7K the LED lights up. Assume [...]
  • OR gate with two 555
    This shows how to OR gate two 555, when one 555 cycles at a low frequency a valve turns on an off, the second 555 [...]
  • Insulation Tester power supply
    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, [...]
  • LM311 Square Triangle Oscillator for PWM
    LM311 is a comparator, It operates from single 5V supply or dual supplies,input current 150 nA, 50 V-50 mA output drive capability. TTL-CMOS compatible output. [...]
  • Ammeter and Precision Rectifier
    Studying current measurement is a prerequisite for many of the measuring techniques. The current parameter mainly specifies the power consumption in a circuit, given the [...]
  • Voltage to Current Source 4-20 mA
    The 0-1V to 4-20 mA Converter published earlier is a current sink, Here is a circuit that is a voltage to current converter but with [...]
  • 555 based Reset Generator
    You must have read all the circuits and explanation on the other pages at delabs to understand this, as i cannot repeat the same thing [...]
About delabs 160 Articles
Product Design - Industrial Automation and Instrumentation. -