Convert RMS voltage to Analog signal + Per Unit

P

Phantush

I am getting LL RMS voltage of 690v AC sine wave from a source. I want to convert it to read this as 690 volt analog signal i.e voltage drops would be read directly as 680...670 etc and not as a sine wave. also want to convert it to "per unit" i.e 690 = 1 and then use it for annunciation etc. What would be the calculation for this? this question may be a lame one but please bear with me.

R

Roy Matson

If I'm reading you right you want to measure the Peak Voltage.

Use a diode and capacitor to convert to DC and measure that. You would need a small drain resistor to make it follow the peak.

P

Phantush

The sine wave input is to be read in from a PLC.

David_2

You need a signal conditioner module to produce a useable signal for PLC (4-20mA) and to isolate the isolate the PLC from the relatively high voltage.

Here's a link to a signal converter that handles inputs up to 1000 Vac.

http://tinyurl.com/pk6mhgg

I do not understand what "per unit" means or what "690 Vac =1" means.

If you need to scale the voltage to some arbitrary scale then you can scale the 4-20mA to whatever units you need in the PLC or HMI.