Last November I started using a Dr. Tester portable pH probe due to my problems reading the different shades of red and orange on the liquid test kit that's so popular. I promised I'd follow up so here's my assessment:
- It works great, is extremely reliable.
- My biggest concern was how well it would stay calibrated. It only required calibration a few times first few weeks and even then it was .1 ph unit. After 3 weeks it was never off again. Don't know how they do it in such a cheap device but sensor technology has improved dramatically in the last few years-maybe this helped.
- It's very quick but you do have to wait 20 seconds or so for the reading to stabilize.
- Reads full range. Phenol red's range is limited to about 7.0 to 8.0 so it is possible to accidentally get very high or very low pH and not realize it.
- The only problem I've had is the readings got very erratic - climbing and dropping the entire scale over and over... I thought it was fried. But I removed the batteries and found a little rusty corrosion on one of the 3 coin type cells. Cleaned it and works good as new. This happens every 3 months or so in the humid pool environment.
Conclusions and recommendations:
- This is a superb device for anybody that has color-blindness difficulties with the red-orange color ranges. It's actually also a good adjunct for the TF 100 test kit for anybody. I like to use the FAS-DPD for chlorine and not have to use the other drop test for pH. I find the oto chlorine test consistently runs lower than the FAS-DPD and I'm pretty sure the FAS-DPD is more accurate.
- Buy a small amount of pH 7 standard solution already made up. It's found on gardening sites very cheap. I got about a quart and that's probably a 10 year supply so get the smaller size.
- There are other brands that seem to have identical electronics. If anybody has experience with them please let us know in the replies. I'd avoid the ones that are around $10 as they are not temperature compensated. $7 more for temp compensation is worth it.
- I'll try some corrosion block on the batteries, that should help.
I hope this helps.