Det-Tronics U9500 Infiniti Gas Transmitter User Manual
Page 26
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10.1
• Inspect the sensor. Loss of sensitivity can be
caused by various factors. One common cause is
by clogging of the hydrophobic or sintered filters by
dirt, oil, paint, etc. Problems of this nature will not
be detected by the transmitter’s diagnostic circuitry
when used with catalytic or electrochemical sensors.
If the filter or the sensor are dirty or plugged, they
should be replaced. When the transmitter is used
with the PointWatch Infrared detector, contamination
of its optical surfaces will be annunciated.
• When calibrating a C7065E O
2
Sensor, the initial
“zero” calibration requires activation of a switch
located inside the sensor housing. Subsequent
calibrations of the sensor do not require switch
activation. Always calibrate the sensor using 20.9%
O
2
if ambient air is less than 20.9% O
2
.
AUTO CALIBRATION PROCEDURE
In the Auto Cal mode, all adjustments are made
automatically by the transmitter once calibration has
been initiated. Auto Cal mode is recommended for all
sensors except Cl
2
and SO
2
. Refer to Table 13 for the
Automatic Calibration Procedure.
O
2
Sensor Calibration
Initial calibration of the U9500C/C7065E O
2
detector
requires removal of the C7065E sensor housing for access
to the zero selection switch. Subsequent calibrations of
the sensor will not require removal of the sensor housing,
nor nitrogen purging. The U9500C will automatically set
the zero cal level even with normal levels of O
2
displayed
during the zero calibration process. Refer to “Calibration
Procedure for Infiniti with C7065E Oxygen Sensor” for
details.
Catalytic Sensor Calibration
Catalytic sensors respond to many combustible gases.
While it is highly recommended that a sensor be calibrated
to detect a single gas, the fact remains that only a few
calibration gas types are available. In addition, multiple
gas hazards may exist.
A known concentration (typically one half of the full scale
detection range of the instrument) of the actual gas or
vapor type that is expected to be detected should be
used to calibrate the system. Det-Tronics calibration
gas should always be used to ensure proper system
calibration performance and accuracy. Calibration gas
should not be used if the Oxygen concentration within
the gas is listed at less than 20% by volume.
A conversion K-factor must be used in the calibration of
the system whenever detection of gases/vapors other
than the gas used in the actual calibration process will
occur. Refer to the “Det-Tronics K-factor Tech Note” for
the current list of Det-Tronics K-factors. The K-factor
represents the relative sensor response ratio of the
calibration gas to the detected gas. The K-factor is used
within the “K-factor equation” to determine the proper
transmitter output level (span setpoint) when the sensor
is exposed to the calibration gas. The K-factor equation
is as follows:
C x K = S
C =
Concentration of the calibration gas in % LFL
K =
Conversion K-factor for the gas to be monitored
with the given calibration gas
S
=
Corrected combustible gas transmitter
calibration span output level (span setpoint)
Example: Gas to be detected: Propane
Calibration gas:
50% LFL Methane in air
K-factor: 1.39
Equation:
C x K = S
50 x 1.39 = 69.5
For proper system sensitivity to propane, the Infiniti
transmitter calibration gas concentration setpoint should
be adjusted to read 69% LFL. When the sensor is
calibrated with 50% LFL methane in air calibration gas
mixture, the sensor will provide an accurate measurement
of propane.
If more than one calibration gas type and K-factor is
listed for a gas that will be detected, generally the
best calibration gas to use is that which provides a
K-factor closest to the value of 1.0 (one). Note that the
presence of Methane gas as a potential detectable gas
is an exception. Always use Methane calibration gas if
Methane is expected to be present within the protected
area.
If a specific gas/vapor and K-factor is not listed within
the “Det-Tronics K-factor Tech Note”, a K-factor can
be determined by Det-Tronics Sensor Engineering
department. Contact the factory for details.