22May2002
Page
17
IX.
Off-Site Sensor Calibration:
The
smarter
transmitter Toxic gas sensors include an EEprom encapsulated inside the
sensor housing. The EEprom retains all set-up parameters (alarm set points, relay
operation/function, etc.) and sensor calibration factors. Therefore, the sensors can be
calibrated in the instrument shop (i.e. off-site) with Mil-Ram
Remote Calibration
Electronics
(contact factory) and the sensors re-installed in the field without further
calibration. Upon installing the sensors, the field installed transmitter electronics
automatically up-loads the calibration data to properly configure the transmitter.
X.
Self-Calibration:
The
smarter
transmitter provides unattended
self-calibration
features whereby every 30
days the micro-controller electronics increments the span calibration based on the typical
life curve for the sensor type. When a field calibration is performed with a gas sample of
known concentration, the life curve is re-extrapolated based on actual calibration data.
Note:
The
self-calibration
feature is intended to supplement and not replace a regular
calibration program using a certified gas sample of known concentration. Although
the sensors are normally quite stable, it is generally recommended that calibration be
performed monthly in the interest of safety. Unusually harsh or severe environ-
ments may require more frequent calibration checks.
XI.
Remaining Sensor Life:
The
smarter
transmitter determines
Remaining Sensor Life
based on actual field
calibration data, sensor life curve and specific electrical characteristics of the sensor. The
remaining sensor life is an approximation and does not replace a regular calibration
program using a certified gas sample of known concentration to validate sensor response.
Near the end of sensor service life, the transmitter will indicate
Replace Sensor
. At that
time the sensor must be replaced with a new sensor to ensure proper calibration.
