The curve shown gives the transmitter
output current as a function of the gas
concentration. If the user connects the
transmitter to a controller other than
the one provided by Oldham
Simtronics, they should be certain that
the transfer curve is fully compatible
with the input characteristics of their
equipment to ensure the proper
interpretation of the information
provided by the transmitter. Similarly,
the controller should provide sufficient
voltage to compensate for any voltage
drop in the cable.
Scope of use
Gas sensors have certain limitations; it is essential to fully recognize these
limitations (see Chapter 10).
Presence of specific components
Vapour from silicone or sulphur-containing components can affect the
catalytic gas detector sensors and thereby distort the measurements. If
the sensors have been exposed to these types of compounds, an
inspection or calibration will become necessary.
High concentrations of organic solvents (e.g. alcohols, aromatic solvents,
etc.) or exposure to quantities of gas greater than the specified range of
measurement can damage the electrochemical sensors. Inspection or
calibration is then recommended.
In the presence of high concentrations of carbon dioxide (CO
2
> 1% vol.),
the oxygen-measuring electrochemical sensors can slightly overestimate
the concentration of oxygen (0.1 to 0.5% O
2
overestimate).
Operation under low oxygen levels
If an electrochemical detector sensor is used in an atmosphere
comprising less than 1% oxygen for over one hour, the measurement
may be an underestimate.
If a semiconductor detector sensor is used in an atmosphere comprising
less than 10% oxygen, the measurement may be an underestimate.
If a semiconductor detector sensor is used in an atmosphere comprising
less than 18% oxygen, the measurement may be an underestimate.
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