Q: Our turbidity meter comes supplied with a bottle of silicone oil. What is this for? Why is it important in the test?
Turbidity meters work by a beam of light shining onto the sample, which is then reflected by suspended particles in the sample. A detector measures the light which is reflected by 90° and this is used to report the turbidity value. Our previous blog post here explains this in more depth.
If the glass sample vial has a scratch on it this will reflect or interfere with the light path, leading to a false result. Remember the scratch may not be visible to the human eye, but could still cause errors.
Putting just 1-2 drops of silicone oil onto a lint free cloth and carefully polishing the vial before placing it into the meter makes sure any scratches are smoothed over, giving a good result.
Some modern meters get around this using different measurement technologies – for example the Hach TU5 series take 1000 readings in a 360° circle around the sample, then average them out. This means if there is a scratch it is corrected for by the averaging, so silicone oil is not needed with these meters. Find out more about this technology in our previous blog post here.
To find out more about turbidity meters and other water testing techniques, follow the links above or contact us with your questions;