Dr. A. Kuntze PH-T Manuale - Pagina 7

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2.1 High resistance test

This test is only carried out with pH instruments. The high electric resisitance of the pH

glass electrode requires an equally high resistance wihtin the whole measuring

system. If the reistance drops, for e. g. due to humidity, the measurement becomes

unstable and tends to drift or wave.

To test the high resistance of the instrument and the cable, the PH-T is equipped with

an even higher internal resistance that can be activated with the key labelled "MegaΩ".

If the resistance is high enough throughout your measuring system, the activation has

no effect - the values displayed by the instrument and the PH-T remain more or less

unchanged. If not, then the value will decrease drastically.

1 - Connect

Connect the PH-T via the adapter to the pH cable of your instrument.

2 - Switch on

Switch on the PH-T by pressing key "ON" for 5 seconds.

NOTE

Switch-on is delayed to prevent accidental activation during transport.

3 - Adjust value

Stay in the mV mode. Adjust the value to approx. 300mV. Your pH instrument should

show now approx. pH 2.

4 - High resistance test

Press the key labelled "MegaΩ". "MΩ" in the display indicates that the high resistance

has been activated.

Focus on the value displayed by the PH-T: if it drops significantly, e. g. to approx. half its

original value, then the measuring system does not provide the required high

resistance.

NOTE

Often the cable rather than the instrument is the source of loss in

resistance - to make sure, repeat the test with a different cable!

NOTE

The high resistance test consumes a lot of battery power - don´t

forget to switch it off by pushing again the key "MegaΩ Ω Ω Ω Ω "!