Metrohm 751 GPD Titrino - Manual (Page 218)

5.2 Connection of electrodes, preparing titration vessel
751 GPD Titrino
215
5.2 Connection of electrodes, preparing titration ves-
sel
Ref Connection for separate reference electrode.
Input is free when a combined electrode is used.
Pol Connection of polarized electrodes.
If measured quantities Ipol or Upol are selected, this
measuring input is automatically active.
Ind I
Ind II Connection of pH, redox, ISE electrodes.
Combined or separate electrodes. Select measuring input
1 or 2 in the Titrino.
Important:
The measuring inputs 1 and 2 have a common reference.
They may therefore be used as a differential measuring
input see below. However, only one reference electrode
can be used in the same vessel!
Pt100/
1000 Connection of a temperature sensor Pt100 or Pt1000..
Differential potentiometry
In potentiometric measurements in media of low conductivity, e.g. in
organic solvents, high-impedance electrode assemblies such as pH
electrodes record noise voltages which arise from stray electrostatic
and electromagnetic fields. Particularly high field strengths occur
through friction at insulators such as plastic floors, synthetic cloth-
ing, etc.; conditions which can appear in every normal laboratory
environment.
Problems of this type can be solved by measurement using a differ-
ential amplifier. Here, the indicator and reference electrode are each
connected to a high-impedance measuring input. It is important to
ensure that both electrodes have identical shielding and are thus
symmetrical with regard to the recording of noise signals. An auxil-
iary electrode provides the electrical connection between the refer-
ence point of the amplifier circuit and the measurement solution.
Recommended electrodes:
Meas.input Manual determinations Sample Changers
Ind I 6.0133.100 pH Glass electrode 6.0130.100 pH Glass electrode
Ind II 6.0729.100 double-shielded
Ag/AgCl reference electrode
6.0729.110 double-shielded
Ag/AgCl reference electrode
Ref 6.0301.100 auxiliary electrode 6.0302.110 auxiliary electrode
Ref Pol
Ind I Ind II
Rear panel:
Pt 100/1000