This information is part of the Modelica Standard Library maintained by the Modelica Association.

This model demonstrates a differential amplifier to attenuate the input voltage to a level that can be handled by the measurement instrument.

Two sinusoidal source voltages with a phase shift of 120° (e.g., two phases of a three-phase system) feed a load resistor. The voltage at the load resistor has to be measured but is too high for direct measurement.

Notes

• The output of the amplifier is inverted with respect to the differential input, as well as attenuated by the factor 1/data.k.
• The influence of the measurement instrument's input resistance on the measurement result is small.
• The current consumption of the amplifier inputs at the source circuit is small (resistor1.i and resistor2.i).
• The common of the source and the common of the amplifier are connected by a ground resistor. In case this resistance is low, a small current is flowing between the amplifier's common and the source's common (resistorGround.i). In case this resistance is high, the amplifier's common is floating with respect to the source's common with a high voltage (resistorGround.v).