and LEDs. When Calibration Alert is enabled, the milli-amp signal output will also be driven to calibration alert output. Perform
a calibration when the device recommends it.
Failure to follow this warning can result in serious personal injury or death.
5.3.1 XCell Sensor with TruCal and Diffusion Supervision (CO&H2S Only)
Sensors with TruCal technology will adjust sensitivity without any manual intervention or calibration, unless called for by the
sensor. If the adjusted sensitivity from TruCal deviates too far from the last gas calibration sensitivity, the sensor will
recommend or, in extreme cases, require a calibration. When a calibration is recommended, the transmitter LED status
indicators slowly pulse green. Users can also enable a Calibration Alert function that will send a milli-amp signal on the analog
output to the control room when a calibration is recommended. When a calibration is required, the status LEDs will flash yellow
and the transmitter will go into a Calibration Required Fault.
With Diffusion Supervision and Calibration Alert enabled, the time between scheduled calibrations can be extended to 24
Months.
If calibration alert and/or diffusion supervision are disabled follow the calibration frequency recommendation set forth in 5.3.2
XCell Sensor with TruCal without Diffusion Supervision (CO&H2S Only).
5.3.2 XCell Sensor with TruCal without Diffusion Supervision (CO&H2S Only)
Sensors with TruCal technology will adjust sensitivity without any manual intervention or calibration, unless called for by the
sensor. If the adjusted sensitivity from TruCal deviates too far from the last gas calibration sensitivity, the sensor will
recommend or, in extreme cases, require a calibration. When a calibration is recommended, the transmitter LED status
indicators slowly pulse green. Users can also enable a Calibration Alert function that will send a milli-amp signal on the analog
output to the control room when a calibration is recommended. When a calibration is required, the status LEDs will flash yellow
and the transmitter will go into a Calibration Required Fault. Without Diffusion Supervision, regular calibration of the sensor
must still be conducted to confirm the sensor inlet is not obstructed.
Actual TruCal sensor performance will depend on the application, background gas exposure, and environment. To validate
XCell sensors with TruCal, it is recommended that users follow their regular calibration cycle and record the “as found” and “as
left” values, tracking the percent adjustment over time. Once a baseline is established, the calibration intervals can be
extended until the percent adjustment is greater than the expected accuracy of the sensor.
5.4 Calibration Types: Zero vs. Span
There are two types of calibration; zero and span calibration.
The zero calibration resets the baseline level reading to zero. If the target gas is suspected to be occasionally present, it is
best to also use a zero gas cylinder during the zero calibration. If the target gas is not present in the atmosphere, an additional
calibration cylinder is not required.
The span calibration is a process that involves first zeroing the baseline reading, then applying a known amount of target gas
so that the accuracy and precision of the transmitter can be adjusted to the known value. The known concentration of gas is
called a "Span Value" because it represents the span or reach of the calibration curve from zero to that value.
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5 Calibration US
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