Conductivity is a temperature dependent measurement. All substances have a conductivity coefficient which varies from 1% per °C to 3% per °C for most commonly occurring substances. The automatic temperature compensation on the MANTECH Conductivity meter defaults to 1.91% per °C, this being adequate for most routine determinations.
Temperature-corrected Conductivity is calculated by:
- Subtract the current temperature of your standard from 25°C (or whichever reference temperature applies).
- Multiply the result by 1.91% which is your default temperature coefficient.
- Multiply the result by the uncorrected conductivity value.
- Add the result to the uncorrected conductivity value. If the sample temperature is higher than the reference temperature, the result of step 1, 2, and 3 are negative numbers so it is a subtraction from the uncorrected conductivity value.
- The result is the corrected conductivity value.
Example: Uncorrected conductivity value is 1200uS, current temperature is 21.4°C, reference temperature is 25°C, default correction factor of 1.91%
- 25.0 – 21.4 = 3.6
- 3.6 * 0.0191 = 0.06876
- 0.06876 * 1200 = 82.51
- 1200 + 82.51 = 1282.51uS <— Temperature Corrected Value for Reference Temperature 25°C
Conductivity readings varying with temperature may be due to the substances under test having a coefficient other than the typical value of 1.91% per °C. To eliminate this variation it is necessary to maintain all samples at the reference temperature by use of a thermostatic water bath or equivalent.
Adjustment may be made by entering the 4510 conductivity meter SETUP menu and selecting COEFF. The reading can then be adjusted to the required value (0.00 to 4.00) by using the keypad. A setting of 0.00 will mean that there is no temperature compensation being applied.
