# Differential Amp

Discussion in 'Electronic Basics' started by chuck, Feb 28, 2007.

1. ### chuckGuest

The batteries are in series and connected to a load? You can't
disconnect the load and simply measure the voltage of each battery with
a simple DMM?

I'm a bit confused by what you are trying to do, Michael.

Chuck

2. ### MichaelGuest

Hi,

I have a bank of 6 6V batteries and I'd like to be able to measure the
voltage across each one. Would the best way be to use a diff amp as the
voltage won't be relative to ground?

If so, could someone please suggest a suitable IC that will won't go into
saturation round the 45V area?

Cheers,

Michael

3. ### MichaelGuest

Hi,

I'm building a robot that has 6 6V batteries as its power source and I'd
like to monitor each battery when the robot is operating. As it's designed
to work from some distance, I need to read the voltage and input it into the
onboard computer computer so it can be transmitted (IE I can't just use a
DMM as I won't be there to read it.)

Cheers,

Michael

4. ### Michael A. TerrellGuest

Resistive dividers, and a mux to an A/D converter. BTDT, and its in
orbit.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

5. ### john jardineGuest

For one diff' measurement it's simple to just use a standard opamp and
resistors to knock the voltage down and increase the common voltage range.
This example would put out 1/10 of the diff' voltage in. Ie 0.60V for a 6.0V
battery. That 6 volts could be sat on top of anything from 0V upto about 45V
10k
___
,----|___|---,
| |
| |
| 5V |
| -o- |
100k | | |
___ | |\| |
( - ) in o------|___|----o----|-\ | Out
___ | >----o------o
( + ) in o------|___|----o----|+/ 0-5V
| |/| o
100k .-. | |
| | -o- --o--
10k| | 0V 0V
'-'
| Opamp is a 'rail to rail' in&out type
--o--
0V

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