ph meter reading abnormal

[andysho]

My ph meter dun seem to be in a good condition

sometimes it read 4 ,5 or even 7

It is non-pen type

is it something wrong with the probe

any advice

[terryansimon]

did you calibrate your meter/probe? could be the case.

[Tanzy]

Such violent swings could mean that the probe is damaged or old, meter running out of battery or malfunctioning. I doubt calibrating will help since if it is a calibration error, the meter should retain it's precision.

[terryansimon]

ah point taken.

[sailfin]

My ph meter dun seem to be in a good condition

sometimes it read 4 ,5 or even 7

It is non-pen type

is it something wrong with the probe

any advice

first of all your probe needs to be cleaned every 2 weeks and the probe changed every 2 years or so. Build up of alot of things will make your readings inaccurate. Remember never to rinse your probe under tap water. Get distilled or RO to do that and never use the same water twice when calibrating

[weileong]

My ph meter dun seem to be in a good condition

sometimes it read 4 ,5 or even 7

It is non-pen type

is it something wrong with the probe

any advice 

Since it is non-pen type. You can try this. I assume yours has a removable pH probe.

With the meter power off, remove the probe.

Short the connector on the meter side with a wire.

Remember to do the above with the power off else you risk frying the op-amp.

Turn the meter on. Check the reading. Should give you near 7.0

If the reading is still jumpy that means the meter spoilt already.

If the reading is stable then the probe is defective. Probably connection is bad. Higher chance that the meter is defective.

If you probe allows you to replace the internal solution which is usually KCL and sometimes AgCL then replace it.

If your probe is old you can try to soak it in warm water abt 60degs for 20mins and stirring the probe slowly in the warm water, this will dissolve the stuffs stuck to the liquid junction on the probe. If this still fails get 1% diluted HCL and soak the probe. If still cannot use then you can throw the probe away.

BTW when the probe is not in use, best to keep in soak in KCL or AgCL depending on the internal solution of the probe.

[andysho]

wow tats sound science sia so many thing

very chim thanks for all the info