How accurate is the Apex pH probe?

[Tbg299]

I have the probes in the magnetic holder in the return section of my sump. I followed the directions and calibrated the pH probe, but it is reading significantly lower than it usually is with my RedSea test kit. With RedSea, it is usually 8.2-8.3. However, the Apex probe fluctuates from 7.95 to 8.1. Which one should I trust?

 

[n2585722]

When you calibrated the probe did you recheck it in the solutions to make sure the reading was correct?

 

[Lbrdsoxfan]

I get it 'close' enough with comparison with a salifert test.

 

[Tbg299]

When you calibrated the probe did you recheck it in the solutions to make sure the reading was correct?

Yes.

 

[Tbg299]

Here is the chart for today. The spike to 8.3 was after I dosed alk.

 

[n2585722]

Is this the first time the probe has been used? if so you may want to wait a couple of days before calibrating it. Another test is to place some tank water in a glass and place the probe in the glass and compare the readings. If the are different then you may have something interfering with the probe in the tank. The readings in the tank and in the glass should be close.

 

[Tbg299]

Is this the first time the probe has been used? if so you may want to wait a couple of days before calibrating it. Another test is to place some tank water in a glass and place the probe in the glass and compare the readings. If the are different then you may have something interfering with the probe in the tank. The readings in the tank and in the glass should be close.

Nope, it's never been used. I installed my Apex a week ago and calibrated all of the probes, except for the ORP. What would cause interference with the pH readings? Microbubbles?

 

[n2585722]

Nope, it's never been used. I installed my Apex a week ago and calibrated all of the probes, except for the ORP. What would cause interference with the pH readings? Microbubbles?

More likely to be something to do with electrical current. The pH probe deals in millivolts so it would take very little to affect the reading. The water in the glass will isolate the probe from the tank so you would be looking for a difference that more than a slight difference when doing this. It may not be the issue but it is an easy thing to check.