Sensorex Dissolved Oxygen

What is conductivity used to measure?+

Conductivity is used to measure the amount of dissolved solids in a solution or the concentration of acid or base.

How does conductivity work?+

This can be a somewhat complex answer. A conductivity sensor has a known AC voltage passed from a "sending" side through the solution being measured and out to the "receiving" side. The current in the circuit is measured. Using Ohm's Law V = IR R the "Resistance" across the water is calculated. Conductivity is = 1/R.

What are the units of conductivity?+

Depending on the range, conductivity is expressed in µS (microSiemens) or mS (milliSiemens). When very low conductivity is measured, (if <0.1µS) it is often expressed as resistivity (Megaohms) rather than conductivity. In the past, conductivity was expressed as in micromhos or millimhos. The mhos units are now expressed in Siemens or fractions of Siemens.

Does temperature affect conductivity?+

Conductivity is greatly affected by temperature. An error of 2 - 5% per degree Centigrade is common and depends on the range of conductivity being measured. Generally, 2% error is most common for above 500uS. Lower conductivity especially values expressed as resistivity (ultra-pure water = 18.2 Megaohms = 0.055 uS) have up to 5% error. Your conductivity instrument will make these corrections automatically if a temperature sensor is used.

How do I choose the proper sensor for my application?+

This can be a daunting question, but can be simplified greatly to make choosing easier.

How do I clean my conductivity electrode?+

Use mild cleaning agents such as detergents or 5% HCl (removes scaling deposits). Always soak electrodes in chemicals and do not use toothbrush or wire brushes to clean since these will effect electrode performance.

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