We have recently purchased a CM3 current logger which I am using to log relatively small currents (approx 3.8A). I am trying to log the current in an electrical resistance coil which will heat by simple joule heating. What I am seeing appears to defy metal physics insofar as the current is increasing with respect to time and therefore temperature (i.e as the coil heats, the current increases)! I have double checked the readings with a non-logging clamp meter which shows the current indeed decreasing as one would expect.
There also appears to be a discrepancy between the two clamp metres with the TA138 reading 3.7A and the mainstream metre recording 3.95A. I appreciate that the response time and signal level from the TA138 clamps will influence the readings and response time, however I would expect that it would take less than 100 seconds for the reading to drop from 3.7A to 0.4A.
Perhaps you could shed some light on this