Schematics of delabs

One of the oldest Schematic Archives on the Web. It was in the form of pdf files in the late 90s. Instrumentation and Industrial Designs by delabs and Generic Application Designs.

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Friday, January 16, 2015

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