General Lab Catalogue - Crison Instruments - #5

The interaction between the sample, the sensor and the measuring Instrument gives an electrometrlc measure­ment.

However, a correct result depends on the technician us­ing the equipment, who must consider aspects such as:

- how the sample was taken.

- the choice of an appropriate sensor, ensuring that It has been correctly maintained.

- the use of a stirrer.

- etc.

In this catalogue we offer sensors, Instruments, accessories and even guidelines for the users of our equipment.

We offer sensors which measure:

- Ion activity, e.g. pH, chloride, fluoride, etc.

- Redox: capacltyfor oxidation and reduction

- Ionic mobility, conductivity

- Partial DO pressure.

- Temperature.

Potentiometry

Measurement ofthe potential produced by a pair of electrodes, the Indicator and the reference, In a specific solution.

Examples: measurement of pH and redox. Titration Is simply the analysis of the variations In potential which a specific substance undergoes when another, known as a titrate, Is added.

Bipotentiometry

Measurement ofthe potential read by a platinum double electrode to which a constant current Is applied. Example: Karl Flshervolumetrlctltratlon.

Conductivity

Measurement of Ion mobility In a solution. An electrical field between two electrodes Is applied to measure It. The anions migrate towards one of them and the cations towards the other.

To prevent changes occurring In the substances, or the deposit of a layer on the electrodes, etc., alternating current Is used.

Amperometry

This measures the current produced In the cathode of an electrode, thanks to the presence of the element to be measured.

Used In DO measurement.

Temperature measurement

Temperature can be measured either as an Independent parameter, or as data to be taken Into account when measuring pH, conductivity, etc. With aPtlOO or Pt 1000 probe, the sensor Is a resistance which varies depending on the temperature. A pair of metals, or thermopar, which generate a temperature-related potential, may also be used.

Burettes

The basic requlrementfor dispensing liquids Is a high-precision mechanism, actloned by an electronically-controlled step motor. Thanks to the high number of steps Into which the length of the syringe plunger Is subdivided, dispensations of amounts of less than 1 pi per step can be achieved.

Apartfrom doslfylng liquids, burettes can also be used In the various methods of titration.