Hi,
I have finished building a DC data logger for monitoring amps from 0-300a and also voltage from 0-30v which will be used to monitor how a vehicle is used to help with Charge balance calculations for the batteries and equipment that I've installed.
I have used an Audruino mega 2560 with an adafruit ADS1115 to achieve 16 bit resolution, plus x2 HTFS 200-P lem hall effect sensors.
My problem is, that now we have done some mapping in the code, at first glance when testing from 0-300 amps, it appeared to follow a proven data loggers accuracy (75mV shunt). I went up in 10 amp intervals and it followed it within a 2 amp range.
I then noticed that if I wait a while (20-30 seconds) on a set amperage, it began to run away with itself and increase in amperage. The runaway seems to start around the 75 amp mark and gets worse the higher I go. So 7 amps out at 75 amp and 22 amps out at 300 amps. This is not a constant, and it will settle back down to the correct amperage after a while, then start to climb again in cycles.
I added a 4.7nF cap between 0v and output on the sensor and a 47nF cap between 0v and 5v on the sensor, but it hasn't helped.
I believe this to be an interference problem but am in danger of running round in circles so just wondered if anybody had tried a similar project and solved the problem before?
Here's a link to the data sheet for the sensor... http://www.europowercomponents.com/media/uploads/HTFS%20200-P.pdf