Update April 2016 dissolvedgas.com
Trace Measurement Ltd
DO analysers (ppb levels)
Traditionally these were calibrated in air (9000 ppb @ 20°C) and the zero was tested either in sodium sulphite solution or pure Nitrogen / Carbon Dioxide
(It was once claimed that you could test your zero in old beer but nowadays it is regarded as a very poor test)
A major problem is that checking the span at 9000 ppb is far from the DO levels seen in beer (< 50ppb)
Using special gases that have low levels of O2 as verification requires time for stabilisation. Bio-
Reference water in cans should provide a better way as it is a liquid like beer, however reference water has long been known to be extremely difficult to make and is often very inconsistent -
Verifiers give you reference water that is totally reliable and instantly available.
With verifiers you get instant answers without any dismantling and the analyser sensor is kept clean
DO analysers (ppm levels in Wort)
Whilst it is common to have mass flow controllers and in-
Checking wort oxygen levels is critical to many brewers but can be very difficult
CO2 and N2 analysers
Verifiers allow instant testing of all types of CO2 and Nitrogen analysers without having to pass gases through the units or dismantling flow cells
Traditionally analysers were serviced on a time-
All time based methods are inefficient at best or just wrong!
At the monthly service either the analyser is working correctly so servicing it is just a waste of time or else it has already failed, which means you have no idea how many incorrect results there have been since the last service.
Brewers who use verifiers only need to service their analysers when they go wrong