Digital Panel Meter Interface

Discussion in 'The Projects Forum' started by Sonny ReVerb, Jul 15, 2008.

  1. Sonny ReVerb

    Thread Starter New Member

    Jul 15, 2008
    Hello All,

    I'm trying to add a Digital Panel Meter (DPM) to an existing circuit. The DPM requires 0-200mVDC input. The input to the interface will be switched to give two different readings; one is an AC current across a 100 ohm resistor (0-200mVAC) and the other is an AC voltage with reference to ground (0-20VAC). The AC is riding on up to 300VDC. I've cobbled together the attached interface from this datasheet:

    I used the attenuator from figure 14 and the AC rectifier from figure 12. I also used two 10uF caps to block the DC.


    Does this look like it will function properly? Since the attenuator receives AC, does it's orientation to the rectifier make any difference?

    Any other suggestions are appreciated,

  2. Pich

    Senior Member

    Mar 11, 2008
    Will you have other circuits tied to the meter? If so you should flip the devider resistors so that there can be a common negative. Capacitors are not necessary at the input but if you want to install a capacitor (one is only needed) try a smaller value and it needs to be non polarized and should be rated to a higher voltage than the circuit will ever see. Also you may want to install clamping diodes at the positive input of the IC.
  3. Sonny ReVerb

    Thread Starter New Member

    Jul 15, 2008
    Thanks, Pich. This does need to be re-worked. You're right about the common ground. I'll try again.