Hanna Phep+ calibration each use?

I got a Hanna Phep+ pH tester last week. I soaked it per instructions, and calibrated with 4.01 and 7.01 solutions. I took some readings on various things.

I stored it in storage solution, after rinsing per instructions. The next day I wanted to take a reading of some beer I was getting ready to rack just because I could. I had extra UN-OPEN buffer so I thought I'd check it again. It was off. I was reading 7.9 in 7.01 buffer. The 4.01 reading was closer at 4.05.

Last Tuesday at my home brew club we calibrated meters. When I checked it at the club it read high in the 7.01 buffer again. IIRC the reading in the 4.01 buffer was 4.03. I had the first reading in the buffers on each one so I don't think it was contaminated. I left it in the buffer for a few minutes to see if it would effect the reading. It didn't seem to.

Anybody have any experience with this particular tester. I only found one post with it even mentioned. Does it have to calibrate every use? Its not a problem if I do, but I thought I could go a day without having to calibrate.

I think you'll be ok as most of the tests you are going to do will be below the 7.0 range and more in the 3-5 range. You say that it is pretty accurate around 4.0 so I wouldn't worry about it too much. I tend to rinse mine before and after use with tap water and shake it dry. Sometimes the off readings might be due to the sample and storage solution mixing together and changing the pH. If you want to be dead on accurate all the time I'd calibrate it every day. If you just want to get ball park and are not worried about the difference between 4.21 and 4.29 I say RDWHAHB

Good point about it being most accurate in the range I'll be taking measurements. Like I said in my 1st I'm not all that concerned about it, but I didn't expect it. I know people who only calibrate them once a year and thats at the brew club meeting we do it.

Thanks for the response. I'm looking forward to using it. That and the new Barley Crusher I got for xmas. Its been cold and snowy in KC, and expecting more snow tonight into tomorrow.