What to do if Hach Measuring Instruments displays W4: Measurement timeout?
- ZzhallSep 2, 2025
If the Hach Measuring Instruments displays warning W4, it means there was a measurement timeout and the accuracy of dissolved O2 is not guaranteed. This can be due to: * The measurement pressure is lower than 3.5 bar: Check the black seal on the piercing unit, the purge gas pressure, the forcing gas pressure and the Goretex filter. * Gas path not airtight: Check the airtightness of the gas path between the piercing unit and the measurement chamber.