Isolation amplifier

Instruments that are applied in the presence of a common mode voltage without an isolation barrier allow ground currents to circulate, leading in the best case to a noisy representation of the signal under investigation.

In the worst case, assuming that the magnitude of common mode voltage or current is sufficient, instrument destruction is likely.

The normal mode component (VNM) represents the signal of interest and is the voltage that is applied directly across the inputs of the amplifier.

Galvanic isolation is provided by the conversion of electric current to photonic flux through the space between the LED and the detector, regardless of the intervening medium.

[1] Isolation amplifiers are used to allow measurement of small signals in the presence of a high common mode voltage.

This capacitance appears as a low impedance to higher frequency signals, and allows the common mode voltage to essentially blow past the barrier and interfere with measurements, or even damage the amplifier.

Instrumentation amplifiers can be classified into four broad categories, organized from least to most costly: For most industrial applications that require isolation, the single-ended floating design provides the best price/performance.

In this application the technician wants to profile the performance of individual series-connected voltages cells, but the need for an isolated amplifier is often overlooked.

A non-isolated differential amplifier can be used but it will have a rated maximum common mode voltage that cannot be exceeded while maintaining accuracy.