I'm working on the power supply of a temperature controller which sends about 5kW of power maximum (230VAC 50Hz) into 3 sets of 12 heaters (actually, 3kW + 1kW + 1kW). I'm at the stage where I need to detect if any of those heaters burns out or shorts. I am currently considering current monitoring with a software algorithm to detect that.
- I have 3 RS232 lines available, and 3 analog inputs (0-10V or 0-20mA) total (unless I add something else but I'd rather not to).
- That leaves me with 1 current monitor for the whole set, or one per heater set. Hence the specs of the current sensor: >21A full scale or >13A full scale, <100mA accuracy.
- Non-invasive technique is required (intrinsically isolated). I don't trust chips like the Allegro ACS709 to be completely short-free over the entire lifetime (15years) because it may be isolated, but still within a very small package (but maybe I should?).
Clampmeters are very appealing because they're definitely non-invasive and they generally have good accuracy. I have found only one which has a RS232 interface though, and the datasheet is quite poor.