pH meter doesn't calibrate correctly??

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sleepyjean's picture
pH meter doesn't calibrate correctly??

My lab has a pH meter and it doesn't calibrate correctly.  When I calibrate it with standard buffer pH4, it will read as pH7; and when I use st. bufer pH7, it reads as pH10.
We checked the standards' pHs and they were fine.

Any idea why? or what we can do??

Any help would be greatly appreciated!

Thanks you!

jackclj's picture
I'm pretty sure that with

I'm pretty sure that with some old pH meters you have to tell it what your calibrating with (pH4, 7 or 10) before you start. In your case, it may be set by default that you will calibrate with pH7 and 10. So any solution you put first will be red as pH7, and the second as 10. There has to be a way to tell the machine that you want to calibrate with you pH standarts of 4 and 7.  Try Google-ing your pH meter brand and model number  and find the user guide.