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1.5 MODIFICATIONS AND SUBSTITUTIONS
Due to an ongoing development program, AMC reserves the right to substitute components and
change specifications at any time without incurring any obligations.
1.6 GLOSSARY
Act Delay The delay in seconds between the gas concentration reaching an alarm
setpoint, and the corresponding alarm level activating.
Alarm Alarm is an audible, visual, or physical presentation designed to warn the
instrument user that a specific level of a dangerous gas/vapor concentration
has been reached or exceeded.
Calibration Calibration is the procedure used to adjust the instrument for proper response.
Calibration
Gas Calibration Gas is a gas of known concentration(s) used to set the instrument
span.
Gas
Concentration Gas Concentration is measured in:
•
PPM
•
%LEL
•
% Volume
Hysteresis A user specified difference, or delta, from an alarm setpoint. Used to prevent
undesired repeated toggling of alarm activation. The concentration must return
above/below the se/
– hysteresis (based on a decreasing or increasing
alarm type) before an alarm level can become inactive. Hysteresis does not
affect the activation (only de-activation) of an alarm, which is based solely on
the alarm setpoint.
LEL Lower explosive limit is the lowest concentration (percentage) of a gas or a
vapor in air capable of combusting in the presence of an ignition source (arc,
flame, heat).
Min Run The minimum time in seconds that an alarm level will remain active, even if the
gas concentration has returned above/below the se/
– hysteresis (based
on a decreasing or increasing alarm type).
PPM Parts Per Million (1% volume = 10,000PPM)
Percent by
volume
Concentration of gas in a mixture expressed as a percentage of total volume.
Span Full range of a sensor i.e. a CO sensor with a full range of 0-100 PPM has a
100 PPM span.
T90 Response Time in seconds to achieve 90% gas concentration reading. This a
typical calibration point that allows for sensor aging, but tends to be less
accurate than a T99 calibration,
T99 Response Time in seconds to achieve 99% gas concentration reading. This is
a more accurate calibration point.
Zero
Buffering Zero buffering is transmitter function which forces the gas concentration
reading to zero when sensor is exposed to low concentration of a gas. The
zero buffer is indicated in the sensor specification.
Zero Gas Zero gas is gas in which the target gas is not present. The presence of oxygen
is required. Clean air is an excellent source for zero calibration. A known gas
concentration can be entered during zero calibration.