Zero is a number that cannot be measured by any instrument or measurement technique.
For example, the zero mark on a ruler has a width to it. If one wanted to measure zero seconds, starting and immediately stopping a stopwatch would still result in a greater than zero time measurement. The same can be said for measuring zero concentration or zero conductivity.
For this reason, every instrument and measurement technique will have a defined detection limit, below which the existence of a parameter cannot be determined.
Hach methods will give an Estimated Detection Limit (EDL) based on the sensitivity value. For more information, see the article titled, "
What is EDL and how is it determined
Method Detection Limits (MDL) can also be determined by the customer. For more information, see the article titled, "
What is an MDL and how is it calculated