Want to control nitrareductor filter with reedox, setting point -250.

Readings change constantly, reedox is about -150 always.

Now I can measure No3 in the aquarium as a result of bad controlling of the nitrareductor filter.

I changed the signal filter to 1, the same occurs.

What can I do to stable up the reading so it can control the filter in the area of -250 -200 that it should be operated?

Please advice.

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