Hi --
--- In "cptdondo" <> wrote:
>
> I'm coming back to play with TS-7xx0 stuff after a few years off....
>
> I've got a TS-7200 with the A/D stuff on board. I'm trying to instrument a
> fridge (I know it sounds weird but I'm working with a high tech fridge on
> batteries and I need to know how much power it consumes in "normal"
> conditions, so the idea is to record ambient temp, inside temp, current and
> voltage over a long enough period to get some valid data.)
>
> Temp and voltage should be pretty easy, but the current is a bit of a
> problem. I need to measure somewhere around 2 to 5A @ 12VDC. I have not
> found a suitable shunt or a way to do this. The fridge has a
> micro-controller that senses the input voltage and adjusts itself
> accordingly, so whatever I do cannot drop the voltage to the fridge in any
> significant way (say no more than .05V).
>
> Any suggestions?
Look at a hall effect current sensor. Could be either a chip (all the current
going through the chip) or a hall effect sensor attached to a ferrite core loop
(current passes through existing wiring, with one wire passing through the
ferrite loop).
The latter is the type used for the clamp-on ammeter attachments for use in
measuring current with basic multimeters, without breaking the circuit.
Obviously the split ferrite core approach would not affect the circuit at all.
Don't get a current transformer, which also has a ferrite core, as they need AC
to work. Hall effect sensors work with AC or DC, and typically put out a DC
voltage proportional to current (ie 1 mV/mA, or 10 mV/A, etc).
regards, ......... Charlie
>
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