03-14-2005, 03:13 PM
Join Date: Jan 2005
I have the Hanna Checker 1 from proaquatica. Good vendor, instant shipping. The pen has worked well, though it does take it 20-30 seconds to settle on a big pH difference (3+ points).
If you do get a pH meter, you MUST get a pair of calibration solutions (called standard buffers) for it. pH7 checks one side, and choose the direction that your tanks go most - pH4 for more acidic tanks, pH10 for more alkaline. The Checker from proquatica comes with three little capsules of standard buffer powder (4, 7 and 10) to make 20ml (be sure to use distilled water to create them - I didn't on the first go-around) for initial calibration. I trusted that the calibration would last a long time, and was horrified when I took a sample to the LFS and found out that the water that my pH meter said was 6.5 was actually 5.3! Both of the calibration screws were off by over 1/2 point. Lesson learned!
I got a set of standard buffers from a laboratory supply firm (I'll post another item in this thread with the address) and paid $23 total (with shipping) for 500ml of 7 and 4. I bought a couple of 29 cent 10ml plastic test tubes at a local science-fair shop, and fill them about 1/4 full to calibrate. I calibrate my pen at least once a week, and use it daily. It has settled down to where it never drifts by more than a few hundredths in a week.