pH Test Issue

[John Brock]

 I have a digital pH tester which is giving me different results than my Freshwater Master Test Kit from API and I'm not sure which to trust.  My digital pH meter measures my Standard Reference Solution of 7.0 and 4.01 spot on each time.  The same digital meter when I measure the water from my aquaponics system reads 6.6 while the Freshwater Test kit is saying my water pH is around 7.6.  I'm wondering if any of you have encountered something like this.  Could I have gotten a bad test kit from API?

Digital PH Meter:

http://www.amazon.com/Digital-PH-80-Handheld-Resistant-Tester/dp/B0...

API Freshwater Master Test Kit:

http://www.amazon.com/API-Freshwater-Master-Test-Kit/dp/B000255NCI/...

[Vlad Jovanovic]

Are you using the bottle labeled labeled "High Range"? If so, use the other pH reagent bottle and see what the test says then... 

[John Brock]

I was using the non High pH or other pH test.  I am starting to think there is something wrong with my Freshwater Test Kit.  I measured again just with both High pH and regular.  The High pH test came in at 7.4 and the regular said 7.6.  I then used my digital pH tester and it says 6.4.  I then used my digital tester on the pH Standard Reference Solution and it came back at 4.0 and 7.0.  I am going to try to figure out how to contact API and see if I can get a replacement.

[Brent Shafer]

strange ?? I have used both digital and chemical testing and gotten strange results with digital when the battery was low. and I have used high end digital testers  which require the probe to be moist 100% of the time. Could the probe on your tester be going out? How old is your dig meter probe? And how expensive? 

[Brent Shafer]

Okay -- just looked at your probe link!!