Hi there,
My first post in the Automotive section, I have also posted in the Pico technology section regarding a suitable scope / data logger for starting current and charging current data logging (amongst other channels / temp / voltages).
My question here is regarding the TA 167 Current clamp which I have just purchased, it is the first time I have used a current clamp so this post is probably a mixture of me learning to use it and my lack of understanding how a vehicle charging system works....
OK, So I attached the clamp to the negative cable with the +ve sign on the clamp pointing to the negative terminal (after zeroing it)
Clamp set on 2000A range
I am using a Fluke 179 multimeter (via a Fluke BP880 BNC to 4mm adapter) set to mV DC
I get an Ignition on reading of +6 mV = 6 Amps
I switch the HRW ON and get +22.5 mV = 22.5 Amps total (16.5 Amps for the HRW alone)
I switch the HRW OFF and turn the heated seat ON and get - +12 mV = 12 Amps total (6 Amps for the heated seat alone)
I repeat this for various items lights etc just to get a feel for the clamp and the various current draws...
I then set the Fluke to MIN MAX mode and carry out a few vehicle starts which show the MAX starting current to be about 340 Amps (+340 mV)
So all seems fairly logical...
Whilst the vehicle is running (still on the 2000A clamp setting) the multimeter shows -16 mV = -16 Amps (No accessories are switched on)
I then run through a similar process of switching the HRW, Lights, AC Unit, Heated seats ON and OFF but I am surprised to see that the values showing on the multimeter hardly change from the initial -16 mV reading that I got when nothing is switched ON, at most it goes down to -13 mV = -13 Amps with a few things switched ON.
Am I just seeing the alternator varying its output to keep a consistent charge on the battery (with -16 Amps) and this is entirely normal or am I doing something incorrectly?
Sorry if this turns out to be more an Automotive charging systems lesson than about the clamp itself, I just want to make sure I understand what's going on before I progress on to trying to datalog these signals
Cheers