I had similar problem with mine. Called Vinmetrica and they suggested a few things to do. They were very helpful. Finally we hit on resetting the unit by taking batteries out. I told them I had already done this but went ahead a did it again.
This time I kept the unit on when I took the batteries out, waited a minute and put the batteries back in and Voila!! it has worked fine since.
Yep, I even went as far as putting new batteries in even though the old ones were a few months old. Didnt' think about taking them out when the unit was on.
I'm calling around 11:00 EST since they are open 8-5 their time. I'll post an update once I speak to them and see if they have any suggestions.
I followed everything here so far..
Reconditioning and cleaning of pH electrodes
Even in normal use and storage, performance of pH electrodes may show deterioration over time, which typically shows up as noisy, erratic or sluggish electrode readings, and/or difficulty calibrating. Assuming the meter itself is working (see “Meter test” below), then there are two main causes for this:
1. Clogging of the reference junction (most likely).
2. Fouling of the glass membrane (happens occasionally, or after prolonged service).
The following procedures will often provide renewed stability and pH sensitivity. If the electrode cannot be restored by one of these methods, it needs to be replaced.
Unblocking the reference junction:
The reference elctrode junction is usually the problem when the electrode can’t calibrate in its expected ranges. This junction is a fine-pored frit that allows electrical contact of a reference electrode with the solution being tested. It can become clogged over time.
1. Soak electrode in hot (NOT boiling!) water, about 60 °C, for 5 – 10 mins. Allow to cool to room temperature then place in pH 4 reference solution for 5 minutes. Try to recalibrate. If this does not work, try remedy 2
3. Soak in 0.1M HCl (note: this can be made by diluting 1 mL of the SO2 Acid Solution with 20 mL DI water) or HNO3 for 1 hour. Rinse with DI water, then place in pH 4 reference solution for 5 minutes. Try to recalibrate. If this does not work, try remedy 4.
4. Soak in 1:10 dilution of bleach in a 0.1 – 0.05 % solution of liquid detergent in hot water with vigorous stirring for 15 mins. Rinse with DI water, then place in pH 4 reference solution for 5 minutes. Try to recalibrate.
Meter test
You want to be sure that the the instrument is responding correctly. A quick test is to simply short out the electrode connector:
1. Disconnect the electrode and put the instrument in pH mode.
2. Short out the electrode connector on the back of the instrument using something metallic, like a paper clip or pin, to connect the center hole of the connector to its outer sheath.
3. With the input shorted out, the reading should be pH 7.00 +/- 0.5. If out of this range, the meter is probably bad. Contact us.
4. Bear in mind that this test is not 100% fool-proof (the instrument might still have trouble reading pH values different from 7.00), but generally if this test passes, it is much more likely to be an electrode problem.
