LTH Electronics MTD75, Руководство по эксплуатации

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Connections
- 34 - MTD75 Operation Guide
Connections
Sensor Input
The MTD75 can be fitted with up to three optional sensor input cards providing Redox,
Electrodeless Conductivity and pH measurement inputs.
Redox Measurement Installation
The choice of the correct type of Redox electrode, how and where to mount it, so that it has
a representative sample of solution are probably the two most important considerations
when installing a Redox system.
The following criteria are of great importance during selection:
The chemical make-up, temperature and the viscosity of the sample.
The use of the correct materials for corrosion resistance.
Position of electrode for robustness and service access.
Ensuring a representative, uncontaminated solution sample.
To ensure correct electrode mounting the following conditions should be observed:
The electrode system can only measure what is in the immediate vicinity of the sensor area
of the probe.
A moderate flow is maintained to provide an “up to date” sample. Excessive flow rates,
however, can cause certain electrodes to rapidly deplete, which will result in inaccurate
readings. In this case a sealed reference is recommended.
Ensure that both the glass electrode and reference are in contact with the sample.
Avoid points where air can be trapped.
Avoid points of high turbulence as air bubbles will affect the measurement.
If the sample has solids present then use a guard or filter to protect the glass electrode.
The glass electrode contains a liquid, ensure that the probe is mounted so that the internal
filling solution is in contact with the glass bulb.
When a new redox electrode is first fitted or changed it may need to be calibrated (see
page 111). Depending on the application it may also need periodic re-calibration, the
MTD75 series provides an inbuilt count down timer which will trigger an alarm when
calibration interval has expired (see page 111).
Care and Maintenance of Redox Electrodes
All Redox electrodes contain an electrolyte solution, gel or polymer that has a limited life in
both operation and on the shelf. The electrode shelf life depends on its storage conditions,
it is recommended that the electrode should be used within six to twelve months after
purchase.
For gel filled, non-flow electrodes the storage boot may become dried out during storage.
This can result in evaporation of the water inside the electrode causing high impedance in
the reference cell. If allowed to fully dry out the operation of the electrode will be
irreversibly damaged. For electrodes in storage it is recommended that every three to four
months the following procedure is carried out: