Jaycar pH meter

I think pH sensors may have a finite lifetime. I don't know anything about the Jaycar unit but I reckon you might be better off sticking with the little (pH/Alkalinity/Cyanuric Acid/Chlorine) dip test strips - $12 for 50 strips isn't too bad and might be a hell of a lot simpler than stuffing about with a pH meter.

Yeah, well, so does the sun. Any idea how long?

Apparently not. The little strips are very inaccurate, show multiple different colours on the one tab - none of them a very close match to the colours on the container - and they can be adversely affected by different water conditions unrelated to pH. There's much less "stuffing about" just poking a probe in the water, especially if you can get repeatable results with one.

Thanks anyway, I'll try sci.chem.analytical.

The lifetime of the device depends on how long the reference liquid lasts inside the sensor. A good quality sensor will last you years, if treated with care. I am not sure how much the jaycar unit is worth, but its probably not going to be a lab grade sensor. However, you may find it fits your needs quite well. Buffer sollutions can be had from industrial chemists for testing, and you may even find them at your local aquarium supplier. I guess you could also take a water sample to your pool shop once a year for comparison purposes.

ITs been a long time since I was in this industry, but IIRC the senors I used to buy were shipped with a little snap on cap filled with distilled water to extend the life. If the jaycar beast comes with such a fitting then keep it fitted, and filled.

Actually, the more i think about this, IIRC The reference liquid is just a ph neutral liquid. I think lifetime also depends on the how long the liquid in the measurment electrode lasts too, which again IIRC is just a ph neutral liquid. I went looking for my old instumentation books but I cant seem to find them anywhere.

I have no idea what principle the Jaycar meter operates on, but even the laboratory grade instruments are high maintenance and prone to failure. The glass membrane which forms the half cell is prone to both contamination and breakage.

What have got against good quality indicator papers?

Thanks Andy, I got a similar response in sci.chem.analytical. Concensus is the cheap meters are erratic when new, and not likely to improve with age :-).