PH Probes and temperature

[hashbrown]

Hi all I just calibrated my 2 ph probes, put them in my water bin with nothing added.

The Ph should be 7.2 however both probs were measuring 6.8 so baffled at this I got my hand held probe put in the bin and this probe showed 7.0.

Trying to get my head around this looked at the temp of the water and it was 8 degrees C.

Calibrated again put in the same bin 150 l of plain water and they all read different. 

So now my head is really spinning, time to do some reading.

I have read that temperature actually affects the reading of the probes themselves not the water and it can alter the reading by up to 8% the water does not change but the probe itself.

What I read states that the solutions that you are measuring must be the same temperature or it could affect the probe reading not the water.

Hope this helps some people out as this could be the problem with deficiencies arising when say altering ph which actually doesn't need to be altered.

More reading for me .

[hashbrown]

So for example you fill your feed bucket with 8 degrees c water from your tap add your feed ph it to 6.5 the solution could actually be 6.7 as the temperature has affected your probe not the water.

[mikeydoughnut]

8c? That’s bloody freezing ….

[catweazle1]

Check the meters auto adjust for temperature. Most stuff is calibrated for 20c. I would make sure your water is around that.

[hashbrown]

1 hour ago, mikeydoughnut said:

8c? That’s bloody freezing ….

Straight out of the tap obviously not turned my system back on my heater is warming it up as we speak.

[BushDoctoR]

I've noticed this also but it isn't too bad with decent meters. My old cheapo pH pen would eventually give a relatively good reading in cold water but I had to leave it in a jug of solution for a good 5 mins to acclimatise. I'm pretty sure it affects my truncheon too, in water below 10c it shows 0.1EC lower than what it is when it's warmed up, I simply take that into consideration when mixing up