i want to perform regular power measurements using my hmc8015.
in terms of the current measurement path: when starting my dut the inrush current is much higher than these specified 60a peak value (cf3: 20a / peak /-60a).
can you tell me a formula to calculate the so called pre arcing time (i²t) to avoid the internal fuse to be blown?
the current measurement path for the higher measurement ranges (500ma --> 20a) of the hmc8015 contains the following main components:
- 10 mohm resistor (maximum peak current: 150a )
- fuse fr10gr69v20 (690v ac / 20a)
the most important component is the fuse in that case. following the specifictions in the datasheet of this fuse, the 690 v / 20 a type has a pre-arcing definition of 69 a²s.
let's assume the peak value for the inrush current would be 100 a and calculate the maximum time our fuse can be exposed to this current.
pa = pre-arcing time in seconds in a/s
pa = i² * t --> t= pa / i²
t = 69 a²s / 100 a² = 69 a²s / 10.000 a² = 6,9 e-3 s
so the maximum time we can expose the fuse to 100a is 6,9 ms.
some other important informations in this context:
- it is also possible to measure currents using the curent clamps hzc50 (30 a / 500 a peak) and hzc51 (1.000 a / 2.000 a peak).
- if the current fuse is broken, the device must be sent in for repair and calibration. this fuse will have influence on the quantity to be measured.