On Sat, 08 Sep 2007 19:32:38 +0200, homebrewdude
> wrote:

> I am trying to calibrate my Hanna ph meter.
> I mixed up new solutions of 4.00 and 7.00
> I hold on till CAL shows up.
>
> It says "use" 7.01
> Then it says "use" "4.01"
>
> After a few seconds it says "WRNG"

Assuming you have put the electrode in correct solutions as asked by the
display content - something went wrong in the second solution. I don't
know Hanna meters, but it is very unlikely to me that they don't show
error message at once after dipping electrode into pH 7.01 solution - pH
meter must recognize the solution before moving to the next one.

Do you have pH stripes, to check if the second solution pH is really
around 4 (and the first one around 7)? Don't bother with high accuracy,
just check if they are around their proper values.

Borek
--
http://www.chembuddy.com/?left=BATE&right=pH-calculator
http://www.ph-meter.info/pH-electrode