Re: mA-hour meter


On 26-Aug-2005, jswayze@xxxxxxxxx wrote:

> I'm working on an amp-hour meter (actually milliamp-hour) and am
> planning on using an Allegro current sensor to measure current from a
> discharging battery under load. I plan on displaying the accumulated
> amp-hours on an LED display, and a PIC will be running the show.

About a million years ago, I built a mA hour (actually a uA hour) meter
using a voltage to frequency converter. There was an app note on a Analog
Devices part that we used in a configuration for measuring current (I don't
remember the part number). The neat thing is that it will integrate any
peaks or spikes between output pulses, and has a very wide dynamic range
(especially if you trim any ofset errors). We wanted to know the long time
power consumption of a device that drew uAs in sleep-mode, and mAs when it
had something to do. If it's for lab use, just connect a frequency counter
and a few passive parts and you're done.

-Hershel
.