PinPoint pH Monitor Question

[Mercer]

I've recently gotten my hands on one from a sale at a local university. However, one of the probes it came with was almost new, and in service... but the device seems to give me strange readings.

If I turn it on, with probe attached out of the water it starts out at 6.15 in dim light, and bounces around up to 6.20. When I place me hand over it to block light, it goes to 6.35, then settles down to 6.3.

Time to calibrate? New probe?

Also, some of the older probes have water inside - will that effect them?

[N38MD]

First of all, I wouldn't pay attention to readings out of water. Erratic readings, while submerged, can be caused by several things - probe going bad, bubbles collecting around bulb, interference with other devices, etc. Using the ac adapter is also a know source of erratic readings.

I would get some 7 & 10 cal. solution and check the probe and re-calibrate. I check calibration every 1-2 months.

Place the probe in a low flow area and make sure bubbles don't collect around the bulb.

To eliminate the possibility of interference, take a cup of tank water and test it with the probe away from your tank, if the reading differs from the in tank reading, your getting interference.

Also, the bulb on the probe should not be allowed to dry out.

Yes, there should be liquid in the probe - they come that way.

HTH

Ron

[Mercer]

Oh goodness!
The newest probe was let to dry out (by me) after I cleaned it, since I figured the town water would make it go screwy. I've placed it back in water.

Most of the old probes have water in them, but the new one has no signs of a liquid in it. Maybe a glue, but no water.

By the way, are the probes fully submersible? (including chord)