Just got a hannah phep ph meter , set it up and did 2 point calibration with pre packaged buffers....7 and 4.01 according to dorections.after calibration is "locked in" , i tested some tap water , then both buffers...the 4.01 tested just that , but the 7 tested like 7.3 . is this normal deviation ?
No, unless it's a 'checker'. The prpbe on that meter is not very stable in my experience. Most Hanna meters have an accuracy (or precision) of 0.1 pH or better. Recalibrate it and see if it works better.
The pHep5 has an annoying habit of shutting down through an auto time; if it powers off you need to recalibrate it. There is a work around. Just press hold. It keeps it up several minutes longer. I wrote a pH meter FAQ a while ago, just search the archives or i can repost.
Joe
Also,
If it is a new meter the probe was probably dry.
The readings are more stable after the probe has been hydrated
Joe Sallustio wrote:
I would add that, in my experience with my Hannah meter, it is important to keep the sensor stored in appropriate storage solution.
I've also found that if the meter gets a little flaky, soaking it for
30 minutes in storage solution, then re-calibrating helps. It often requires two successive two-point calibrations to get it accurate.
The guy at grape and granary said this meter wouldn't need calibrated each time I use it...is this accurate?
Must be a different Hannah than any I've used. Mine needs calibrating on any day I intend to use it - if I expect the readings to be accurate.
I actually calibrate mine twice before using. And I calibrate it everyday I plan on using it.
AxisOfBeagles wrote:
No, it's not accurate. You are really calibrating the probe, not the meter. You need to get the offset and slope set right for the readings to mean anything. The pH7 buffer sets the offset and the pH
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