The LDO dissolved oxygen sensor from Hach has made measuring DO in many samples much easier. Its robust and simple to use. However you need a new cap to calibrate the unit once a year, so which one do you need?

There are three versions in common use with our customers:

The original HQ10 and HQ20 Replacement sensor cap  part Number HH/51812-00

The New HQD range including the HQ30 and HQ40 Replacement sensor cap part number HH/57911-00

Process LDO Replacement sensor cap part number HH/58112-00