Each single sensor is plugged into an individual printed circuit
board (PCB) that contains control electronics for converting the
raw detection response into an analogue voltage level, so that it
can be easily integrated into the data acquisition architecture. For
the electro-chemical sensors this is completed by commercial In-
dividual Sensor Boards (ISBs) produced by Alphasense. These
control boards maintain the potential between the working and
counter electrodes, the biasing on a reference electrode to induce
reduction/oxidation of the target, and a current loop transceiver
for conversion of the ampero-metric signal into an analogue vol-
tage. The Clairair optical sensors are also controlled using a com-
mercially-produced PCB called Cirius X, which has an on-board
temperature/pressure monitor and drive for the infra-red sources.
The Mocon photo-ionisation detector includes a circuit for con-
verting to analogue voltage within the physical cylindrical pack-
age, so that an in-house constructed break-out PCB was all that
was required. The above control measures remove the influence of
some environmental effects that the detectors are sensitive to,
thus helping to allow for ppm- and ppb-level resolution.