Picaxe multimeter

[Newone]

Hi folks,

Trust everyone has had a great Christmas.

Is there such a thing as a picaxe powered multimeter. I am needing to be able to measure voltages up to 15V DC with currents up to 50Amperes. Is there such a thing?

Just to fill you all in, I am needing to monitor the discharge rate of car batteries.

 

[eclectic]

37 hits, using

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and use the terms

Discharge monitor


There are probably other combinations of terms as well

e

 

[AllyCat]

Hi,

The "50 Amps" is likley to be the "difficult" part of the design, so we (or at least I) need to ask for some more details.

Do you require a fixed (built-in) meter or a genuine "portable multimeter". What accuracy/resolution do you need, is the current bi-directional (charge/discharge), and is an accurate "zero" required? What voltage drop across the current-sensor can be tolerated (if small, an Op-Amp will probably be needed)? Is 50 Amps the absolute maximum current (a car starter motor can be ten times that)?

Three possible "solutions" immediately come to mind: 1) Obtain an accurate resistor/sensor of a few milli-ohms, or 2) Measure the voltage drop across a known length/diameter of copper wire and compensate for the temperature coefficient of its resistance, or 3) Measure the magnetic field from the wire with a linear Hall-effect sensor (calibration required).

Cheers, Alan.

 

[Billo]

Have a look at the ACS756 current sensor. It might fit the bill for the current sensing part. A voltage divider would work well for measuring 15V.