Result 1B: Method for quick evaluation of the accuracy of conductivity meters

In the previous lab note (Result 1A), we evaluated the performance of commonly available and inexpensive conductivity meters by comparing their readings against an accredited lab. Only 2 out of the 5 meters tested satisfied the requirements of accuracy. In practice, it may not be convenient for citizen scientists to send samples to an accredited lab each time they procure a meter due to high costs involved or the unavailability of a lab. In such cases, testing a calibration standard solution can be a quick and reliable method for screening the performance.

We procured a calibration standard with a conductivity of 1413 uS/cm and tested the 5 devices.

 

Calibration Standard

Out of the 5 devices tested, 3 of the devices had an error <3%, demonstrating a high level of accuracy. Consistent with Result 1A, the devices that performed poorly against lab tests, again showed a poor performance with the electrolyte standard. Given this observation, we conclude that a calibration standard is sufficient for a quick evaluation. However, we note that other calibration standards are also available with lower and higher conductivity values. Depending on the use case, they can be used in combinations to arrive a robust standard curve for the meters.

Based on these results, only 2 of the testers were retained for further testing.