Adding DC to 100Vrms AC.

[cyaniccypher]

Hello,

I have a 100Vrms AC signtal that varies in frequency from 40hz to about 15khz. I need to add a DC current (5V@5mA max) to this signal what is the best way of going about to do this. The signal is single ended and swings between +-141V around ground.

Help is much appreciated.

Thanks;
Leo

 

[erikl]

Simply add an ungrounded DC power supply (e.g. from a USB AC wall adapter, or from a battery) in series with your AC signal.

 

[cyaniccypher]

I forgot the second part of the question which is more important. How do I measure the DC on the line. It is quite difficult to filter out out 100Vrms signal.

Thanks;

 

[BradtheRad]

An ordinary analog voltmeter set on a low DC range. It will respond to average value. This means it will not show the AC component.

A digital meter may give inconsistent readings if you feed AC into a DC range.

Will the 100 V AC blow components in the meter when it's on a low DC range? Say your meter is 20,000 ohms/V. On the 10V range it presents 200k to the incoming signal. 100V will force 1/2 mA through resistors in the meter. For a total of 50 mW. Should be safe.