AC Voltage Measurement, Intelligent Devices

AC Voltage Measurement, Intelligent Devices

The accurate measurement of AC Voltage is complicated by the necessity to minimize the burden the measuring instrument places on the primary circuit. The incorporation of a 1:1 current style voltage transformer in the AC voltage measuring circuit offers several advantages.


  • A minimal burden on the primary voltage circuit, with essentially zero primary circuit load,
  • Isolation of the primary AC circuit and the secondary output signal, and
  • Exceptional accuracy with a minimal phase shift.

The AC current style voltage transformer is designed with either a 1mA to 1mA or 2mA to 2mA ratio. An example of the implementation using an operational amplifier I/V (current to voltage) circuit or a resistor sampling circuit;

The input resistor R limits the current to the 1mA or 2mA input. An application note document provide additional information – Application Note 1:1 Voltage Transformer (pdf 510kb).
The TV31 with UL Recognition Certification is an example of a current style AC Voltage Transformer.