Cookies on the OMEGA websites
We use cookies on this website, these cookies are essential for the website to work correctly.If you continue without changing your settings, we'll assume that you are happy to receive all cookies on this website.To find out more information about these cookies please click here.
CLOSE
Free Phone 0800 488 488
International+44(0) 161 777 6611

# Conductivity and Resistivity

## Introduction to Measurement and units

Conductivity measures the ability of a solution to conduct an electric current between two electrodes. In solution, the current flows by ion transport. Therefore, with an increasing amount of ions present in the liquid, the liquid will have a higher conductivity. If the number of ions in the liquid is very small, the solution will be "resistive" to current flow. AC current is used to prevent complete ion migration to the two electrodes.

In this article how the conductivity is measured is more detailed explained.

Conductance = 1/Resistance
Conductivity unit: mho = Siemen
Normal unit of conductivity measurement is:
1 micromho (µmho) = 1 microSiemens (µS),
1 millimho (mmho) = 1 milliSiemens (mS) = 1,000 microSiemens (µS)

Resistivity unit: ohm
Normal unit of resistivity measurement is:
megohm = 1,000,000 ohm

## Conductivity units conversion:

20 microSiemens (µS)
= 20 x 10-6 S
= 2 x 10-5 S
= 2 x 10-5 mho >

1 ohm/2 x 10-5

=1/conductivity
= 1/2 x 10-5 ohm
= 0.5 x 10-5 ohm
= 5 x 10 4 ohm

## Conductivity and Resistivity (NaCl and CaCO3 Solutions at 25°C)

 ppm as CaCO3 ppm NaCl Conductivity micromhos/cm Resistivity megohm-cm 1700 2000 3860 0.00026 1275 1500 2930 0.00034 850 1000 1990 0.00050 425 500 1020 0.00099 170 200 415 0.0024 127.5 150 315 0.0032 85.0 100 210 0.0048 42.5 50 105 0.0095 17.0 20 42.7 0.023 12.7 15 32.1 0.031 8.5 10 21.4 0.047 4.25 5.0 10.8 0.093 1.70 2.0 4.35 0.23 1.27 1.5 3.28 0.30 0.85 1.00 2.21 0.45 0.42 0.50 1.18 0.88 0.17 0.20 0.49 2.05 0.13 0.15 0.38 2.65 .085 0.10 0.27 3.70 0.042 0.05 0.16 6.15 0.017 0.02 0.098 10.2 0.012 0.015 0.087 11.5 0.008 0.010 0.076 13.1 0.004 0.005 0.066 15.2 0.002 0.002 0.059 16.9 0.001 0.001 0.057 17.6 none none 0.055 18.3

## Probe Constants

Probe constant defines the volume between the electrodes. Solutions with an extremely high conductivity require a sensor with a probe constant greater than 1.0. Solutions with extremely low conductivity require a sensor with a probe constant less than 1.0. The greater the distance between the electrodes, the smaller the current signal.

 Conductivity (Micromhos/cm) Resistivity (Ohms-cm) Dissolved Solids (ppm) .056 18,000,000 .0277 .084 12,000,000 0.417 .167 6,000,000 0.833 1.00 1,000,000 .500 2.50 400,000 1.25 20.0 50,000 10.0 200 5000 100 2000 500 1,000 20,000 50 10,000

Conductivity | Related Products
We noticed you are from the US. Visit your local site for regional offers and live support.