eric_s wrote:Hi,
We noticed a slight current reading error on PDM15. For instance, according to the log pulled from ADL3 our radiator fan draws a steady 5A but directly measuring the current with a multimeter connected in series with the fan shows a steady draw of 6A -- tried with other meters and had same result.
Was wondering if anyone can shine a light whether it is possible to calibrate (if possible) the readings?
Thank you.
Eric S.
There are at least three ways to 'measure' the currrent... (that I can think of).
One would be to measure the impedence of the load and compute the current draw.
This would be prone to error if one did not know the voltage.
e.g. a 1-Ohm load would have 12-A at 12V and 14A at 14V.
So I could envision that is the current was computed using 12V and the stsyem is running 14.X-V then you could have 20% higher current from the 20% higher voltage.
So without some input as to how the current is measured, then I would suggest putting a know resistor on an output, and then try using a big dimmer switch on the front end and vary the voltage and observing the PDM's stated current with the measured and comuted current.
If it was varying then one could compute the actual current as:
Current(actual) = Current(PDM)*(Voltage/12V)
But this is all just a guess...