Although the average was zero, each interval had a maximum (and a minimum) reading. In this graph, my APM is displaying a flat zero line indicating the average but also the maximum value.

You do so via the seek method, which takes a single parameter that indicates where in the file you want to start reading or writing (for example, zero indicates the start of the file).

Finally, after each sampling and cleaning sequence the measurements’ zero point ischecked with a water freeness measurement to make sure the next reading isrepeatable.