Current probe CR8448-2500-N

I’m trying to use a current probe (model CR8448-2500-N), a simple calibrated magnet.
I want to read electrical consumption on a alternate current (national network) that supply an uninterruptible power supply, plugged to a battery. The purpose is to have a scientific measure system, supplied with home current but also able to keep running if the network goes off during several hours.

The current probe is connected to a Campbell Scientific datalogger (model CR310) that read the probe. On this datalogger I also installed a voltage divider bridge that allow me to know what is the battery voltage (to know the level of load).

And after some days, I put all data in a graphic.

First graphic is the magnet response in mV, the second one is the divider bridge in mV too (It’s a 12V battery, I don’t remember the multiplier value but it doesn’t matter here).

The system is switched off of the elec. network 4 times / day (the 4 peaks visible by day).

The voltage divider is working well but I can’t understand the read of the magnet : I should have a read of zero (or near of 0) when the system works on the battery (and that seem to be ok) and a read of something above zero when when the system is supply with the electrical network ; even lot when it turned on (reload battery + supply system) and a little less when system is on a cruising mode (battery loaded, and elec. network supplied).

But the magnet seem to respond very chaotically and alternate + and - random value.

I add that I test this with a traditional ammeter reader and I have a good measure, just as waited, but not with the magnet.

What do you think about it ?



The output of the CR8448-2500-N is a signal that represents instantaneous current flow, which in a typical AC circuit is constantly changing and reversing direction 50 to 60 times each second. This is different from most ammeters, which provide an average value over some amount of time.

The CR4110-25 is an example of a similar device that provides an output that is averaged over time, similar to a common ammeter. A sensor of this kind would probably be more useful in an application where a person is recording measurements at a slow rate.

Thanks for you answer,

I was efraid that it was it… that’s a serious problem, Digikey advice me this specific model to do exactly what I have explain above.
I bought 20 units of the same model that seem to be useless in my application. What a lost of time…

I will check on the datalogger if there is a way to make an average regardless of the sign. I think (hope) there is. Just hope that the 50Hz will not be too fast to read…

Thanks to confirm me that :wink:

(If I find a solution I’ll post it here)

Hi again,
fortunately, there is a specific function in the datalogger Campbell Sci. that use V RMS max, and I don’t know what it is …
I have again little adjustment to do ; the intended magnet was a model CR8459, and I have a CR8448, not exactly the same ; I guess there is some multiplier or resistance value to tune in the prog.

But I have serious clue to making something pretty cool now.
Bye !

I believe you can use the CRBasic in the CR310 line of dataloggers to modify the raw data as it is being collected (it’s one of the main advantages of using their multi-thousand dollar loggers vs. the few hundred dollar alternatives).

yes I use CRBasic (much easier way to code the CSI datalogger), and there is a special function to read alternating current (ACPower instruction), not to reading a 50Hz supply with a 20mSec scanning interval synchronized on the electric network (too difficult).

But, the function is normally used with a CR8459 magnet (-2000-N) and I suspect than the magnet sell CSI (of this model) have a little customization with an internal resistance different from the original. And because of this, the function is not usable on the original 8448-2500-N, even with different variable.
But I found another way, I think, using another function but a lot more complicated to program.
But it is so :slight_smile: