Conductivity Standards

Conductivity Standards is the generic name given to a range of Standards used for calibrating instruments. A Standard is used to set an instrument at whichever level is required and a user will choose the most relevant ones according to what is to be tested.

Conductivity Standards are usually measured at 25 degrees Centigrade although it is possible to use them at higher or lower temperatures, but this will affect the results.

The lowest Conductivity Standards are about 74 microsiemens at 25 degrees Centigrade. They are usually set at two points so, for example, to measure a 150 test solution, they would be set either side of 150.

Conductivity Standards are made up of weak solutions of Potassium Chloride in water. Lower level Standards are extremely dilute and can be measured in parts of a gram per litre of water. Higher level Standards are usually measured in millisiemens per litre, with the highest Conductivity Standard going up to about 24.8 millisiemens. At the higher level, results are less accurate.

Small amounts of Conductivity Standards are used at any one time, this being enough to calibrate an instrument. However, most instruments require daily calibration so even though only a small amount of Conductivity Standards is used at a time repeat calibrations require a regular supply of Conductivity Standards. Most Conductivity Standards are sold in 500 ml or 1 litre pack sizes.

Conductivity Standards by their nature must be accurate and many are traceable to N.I.S.T. Standard Reference materials. The material used to contain Conductivity Standards must be chosen carefully as this can affect the material inside. H.D.P.E. bottles are usually used to contain Conductivity Standards as High Density Polyethylene (H.D.P.E.) allows the contents to remain accurate.

Conductivity Standards are clear and colourless and are used to measure impurities in water. Pure water has a Conductivity reading of zero although in practice, this does not happen. This is because by exposing pure water to atmosphere, for example when you taken the lid off a container of water this immediately exposes the water to any impurities in the air, which the water absorbs. Pharmaceutical grade water with a Conductivity Reading of less than 5.1 microsiemens per cm is often used for Conductivity Standard applications.

As with any chemical material, care should be taken when working with or handling Conductivity Standards. Personal Protective Equipment (PPE) should be worn including protective clothing, safety shoes, approved eye protection and appropriate gloves. Conductivity Standards should not be ingested, inhaled or allowed to come into contact with skin or eyes. Medical attention should be sought in the event of an accident or spillage.