Digital Panel Meter common or floating ground

[b1miller]

I am working on a temp sensor circuit using one of the common DPM modules. How about a clear explanation of the difference between the common and floating ground models. Since I need to offset the V- terminal by 2.554V, it would appear that I need to use the floating ground version. My V+ terminal would then read the 1mV/deg. F from the sensor and give me a direct reading in degrees F. Is my theory correct?

[evahle]

Hi B1.

I used to experiment with these meters quite a bit a few years ago. I'm not sure if my memory is all that great, but by using a +/- 5v supply and making one of the supplies adjustable, you can affectively remove the DC offset.

I've included an equivalent circuit schematic that should give you a better idea how the meter works.

The LCD DPM uses an equivalent IC to the now obsolete, ICL7106.

You should be able to still get a datasheet and app notes.

Hope this helps!

evahle