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A Guide to Conductivity Electrodes

Used in conjunction with a conductivity meter, conductivity electrodes measure the electrical conductivity of a solution. Here's the Sonic Supply guide to conductivity electrodes!

Conductivity Meters

Available in benchtop or portable models, conductivity meters measure temperature, the electrical conductivity of water or other solutions and total ion concentration.

They can measure nutrients, salts and impurities in uses such as:

  • Hydroponics (farming in a nutrient solution instead of soil)
  • Aquaculture (the farming of fish and other aquatic animals)
  • Aquaponics (water flows between a plant growing bed and aquaculture tank, allowing fish waste to supply the plants with nutrients)
  • Freshwater systems

Conductivity meters require the use of conductivity electrodes – also called conductivity probes – as the sensor is placed within the water or solution. It’s measured in either micromhos (μ℧) or microsiemens (μS). The units are actually the same – only the name and symbols are different. In the U.S., we typically use micromhos, while Europeans usually use microsiemens.

How to Calibrate Conductivity Electrodes

Calibration requires just three items: deionized water, plastic cups (metal disrupts the meter) and a calibration standard solution. The calibration standard used depends on the various ranges of conductivity being tested.

After setting the conductivity meter to calibration mode, rinse the probe with deionized water in a plastic cup, then insert the probe into another plastic cup filled with a calibration standard. The probe should settle in the standard solution for at least a minute.

Rinse the probe again, this time with a second sample of the standard solution, then use a third sample of the standard solution to calibrate.

Adjust the cell constant until the meter’s display shows the specified value. Recalibrate when you change ranges of conductivity.

How Often Should Conductivity Meters be Calibrated?

There aren't specific guidelines for how often you should calibrate your conductivity meter, as it’s dependent on each application's accuracy requirements.  For measurements that require a very high level of accuracy, your conductivity meter should be calibrated prior to every measurement.  However, for more general use in typical laboratory conditions, once a week is fine.

Cleaning & Storing Conductivity Electrodes

To clean the electrodes, just rinse with distilled water and blot dry with a paper towel. If the probe’s cell surface is contaminated, it can be soaked in water with a mild detergent for about 15 minutes, then soaked in a diluted acid solution for another 15 minutes before rinsing with distilled water.

While calibration requires deionized water, cleaning uses distilled water. Both are purified water, but they’re purified in different ways and have different uses.

Deionized water is treated chemically to remove all mineral ions (i.e., all of the dissolved mineral salts). Distilled water is boiled until it evaporates, leaving the impurities behind, and is then recondensed.

The electrodes may be stored wet or dry. If stored dry, they’ll need to be reconditioned before the next use. To condition an electrode, place it in a standard solution or tap water for 30 minutes to an hour with power running to the electrode.

Selecting the Brand of Conductivity Electrodes

When purchasing conductivity meters and conductivity electrodes, be certain both are made by the same manufacturer. The pin configurations and type of thermistor used for temperature compensation differ between manufacturers, as will the cell constant.

Sonic Supply’s selection of electrodes is manufactured by trusted laboratory instrument specialists, such as Bante Instruments.

If you have any questions about conductivity probes, call or email us. We’re here to help!

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