My Pinpoint Monitor Reading Is Off?? Not sure...

demariners · 09/07/2012, 07:21 PM

So I got a pinpoint pH monitor and also went out and bought a Milwaukee pH pen. I calibrated both using the same solutions (7.0 and 10.0). When I place the pH probe into the 7.0 it reads 7.0, and 10.0 respectively. When I do the same with the pH pen it shows 7.0 and 10.0 respectively as well. So both should be calibrated properly.

So my issue is I place the probe in the sump water and I get 7.6-7.7 then I place the pH pen in the same spot and get 7.9-8.0. I have done this test with the tank water in a cup also. Are these pinpoint monitors usually a little low on the readings? I am not sure which one to trust?

fda483 · 09/07/2012, 07:51 PM

You have to look at the specs for both units. Most likely they are at least +/- 0.2 pH units accuracy. If so the readings are not too far off. Probes also seem to drift a bit more in salt water than in buffer solution.

Joe

demariners · 09/10/2012, 10:48 AM

Well, still having issues. When i move the BNC Connector around the numbers jump back and forth and back and forth. Maybe the unit is defective.

09/07/2012, 07:21 PM	#1
demariners Work In Progress Join Date: Aug 2005 Location: Arizona Posts: 972	My Pinpoint Monitor Reading Is Off?? Not sure... So I got a pinpoint pH monitor and also went out and bought a Milwaukee pH pen. I calibrated both using the same solutions (7.0 and 10.0). When I place the pH probe into the 7.0 it reads 7.0, and 10.0 respectively. When I do the same with the pH pen it shows 7.0 and 10.0 respectively as well. So both should be calibrated properly. So my issue is I place the probe in the sump water and I get 7.6-7.7 then I place the pH pen in the same spot and get 7.9-8.0. I have done this test with the tank water in a cup also. Are these pinpoint monitors usually a little low on the readings? I am not sure which one to trust?

09/07/2012, 07:51 PM	#2
fda483 Registered Member Join Date: Nov 2002 Location: River Vale, NJ Posts: 92	You have to look at the specs for both units. Most likely they are at least +/- 0.2 pH units accuracy. If so the readings are not too far off. Probes also seem to drift a bit more in salt water than in buffer solution. Joe __________________ Joe Current Tank Info: 200gal Reef (in wall/basement sump)

09/10/2012, 10:48 AM	#3
demariners Work In Progress Join Date: Aug 2005 Location: Arizona Posts: 972	Well, still having issues. When i move the BNC Connector around the numbers jump back and forth and back and forth. Maybe the unit is defective.