Conductivity

Conductivity is a way to measure inorganic materials (such as calcium, bicarbonate, nitrogen, phosphorus, iron, sulphur and other dissolved minerals) in a water body by measuring water’s ability to pass an electric current.

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We can, therefore, notice a jump in conductivity as a possible indicator of pollution (e.g. nitrates, phosphates, salt from roads all affect readings). Further lab testing is required to confirm pollution sources. Some ecosystems have naturally high conductivity based on their bedrock, so it is important to get baseline values before drawing conclusions.

Some common values

Distilled water

0.5 – 3 µS

Melted snow

2 – 42 µS

Has effects on fish reproduction

over 500 µS

Tap water

50 – 800 µS

Potable water

30 – 1500 µS

Freshwater streams

100 – 1,000 µS

Industrial wastewater

10,000 µS

Sea water

55,000 µS

E.g. Most readings for the Ottawa river are below 100 µS, but near a storm sewer could have conductivity values over 2,000 µS (or 2.0mS).

What about ocean water?

Conductivity reading for ocean water is about 55,000 µS.  This meter won’t record that high. Use a refractometer instead to record salinity. See our Ocean Explorer for details.

 

How to

Conductivity is measured by placing a conductivity probe in the water and measuring the flow of electricity between the electrodes.

  1. Pull off bottom cap. It can be a bit tough, but it’s a ‘pull’!
  2. Turn on the conductivity meter by pressing the top buton.
  3. Dip conductivity meter into the water. Do not dunk the whole device in as the battery is near the top.  Hold in the water for 2 minutes, swishing it around lightly. Continue until temperature and conductivity remain steady for 30 seconds.
  4. Press the ‘hold’ button (middle button). (tip: If you get a reading of 10 or less,you have not removed the cap or you have taken the sensor out of the water before reading)
  5. Pull up meter and read the conductivity and temperature readings. We record in µS
    (micro-siemen), so check the units. If you get a reading like
    1.3, it is converting it to mS
    (milli-siemen) and you must multiply 1.3 by 1000 and record 1,300 in your form.
  6. Make sure you turn off the device after use to preserve battery life (top button).

Top value is conductivity, and the bottom value is temperature.  So, this reading, done in winter in a stream has a conductivity of 161 and a temperature of 15 °C . These devices always adjust the conductivity based on temperature, so it’s important to record both values. These readings only work while the sensor is in the water.

 

 

 

 

 

How-to test for conductivity quick start (1:47)

 

Ask an expert: Conrad Gregoire, Chemist, introduces Conductivity (3:20)

Ask an expert: Conrad Gregoire, Chemist, how to test and use a reference to make sure you’re accurate (10:27)

 

How to create callibration solution (with Carleton University Environmental science students, Sofia and Benson) COMING SOON

 

This conductivity meter can be found in…

 

Research

This device has been compared to professional probes with a 99% accuracy level.