Hello again

Ok my mistake. It is the pump in the tank that is causing the problem. when I remove the pump or put the probe in a sample like you said, I get a stable reading

Is there a way around this problem? earth the water or something?

Hello and a merry christmas to you all and a happy new year.

I have tried just measuring a water sample, but it made no difference. I have also tried diferent probes but still no better.

could the drdaq board itself be faulty?

Yes I have tried using pico log and I get the same fluctuation. You mantionded the fluctuations are 50hz wich is what mains is, but the board is powered by the computers com port. So how do we pinpoint the fault, is it a fault within the board or a fault with the supply to the board?

I read in another post, to test the board short out the ph terminal and if you get a reading of around 7 then it's ok. I have done a calibration look-up tabe, but it made no diference. the only way I can get a reasonably stable reading, is if I set it to display the average, is that what you are sup...

Hi not sure what settings file you require all there is is a bunch of .dll's.
I have not as yet, done a calibration.
I have tried using a diferent probe but get the same results.
I have also shorted out the terminals and I get a stable reading of 6.9

Thanks
Gareth

The external temp sensor no1 is in the water, but I'm not sure if the software is set to compensate, I couldent see any settings to do this.

If I set it to display the average reading it displays exactly what my handheld devise displays. is this what I need to do always.

Thanks
Gareth

Hi I have just started using my DrDaq data logger, and I was taking PH readings from my fish tank, but the readings fluctuate from 6 to 7. constantly going up and down, on the graph it looks like a wave going up and down. anyone have any ideas why the reading is so unstable. all the equipment is bra...