[Dave Willis]

Do they have to be recalibrated if you change the batteries?
Mine are eight years old now.

[LWC]

Ive never re calibrated one in the whole time of using pole system

[Smudger]

I don't think so, but worth checking

Darran

[Mick Kent]

I have 3 tds meters and all say 000 but when the tds creeps up they all show different readings, 1 would say 002 another 006 and another maybe 020. I dont know which 1 is the correct reading so i just change resin a few fills after resin creeps up.

[Spruce]

I have 3 tds meters and all say 000 but when the tds creeps up they all show different readings, 1 would say 002 another 006 and another maybe 020. I dont know which 1 is the correct reading so i just change resin a few fills after resin creeps up.

You can buy calibrating fluid with a known tds and test your meter.

http://www.daqua.co.uk/calibrationfluid.htm