Technical data

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Value in “measuring unit” means that the displayed figure stands for either % LEL or Vol.%. Reading in
Vol.% applies only to the gas ammonia.
Alarm Threshold (only for type CC28 DA)
The CC28 DA provides two alarm thresholds. An alarm is triggered, if the gas concentration exceeds
the preset limit value (adjustment in service menu). Exceeded thresholds are indicated by means of
the LED bar over the display, the display illumination and a buzzer. When the first threshold (A1) is
exceeded, the display illumination and the LED bar are alternating in low frequency. The display
reads the currect measurement value and A1 alternately.
Exceeding the second threshold (A2) activates the display illumination, the LED bar and the buzzer
alternating in high frequency. The display reads the current measurement value and A2 alternately.
Resetting the threshold alarms can be done automatically or manually, i.e. non-latching or latching
alarms, depending on the function setting in the service menu.
The function of the buzzer is fixed and cannot be changed: Activation by alarm 2, automatic reset
when the concentration has fallen below the second threshold, always resettable.
Pressing key
QUIT
MENU
allows to reset a latching alarm, if the gas concentration has fallen below the alarm
threshold.
Ambiguity Alarm
Due to the detection principle it might be possible that a very high gas concentration dissipates the
oxygen in the cell, thus resulting in a lack of oxidation and a reduced signal, although the sensor is
exposed to a gas concentration which is clearly above its detection range. For avoiding false signal
evaluation, the CC28 provides a warning from ambiguous sensor signals.
This alarm is triggered by exceeding of 112 % LEL and by recognition of a defined rise of signal
(Delta Alarm).
The ambiguity alarm is indicated by the fault LED flashing quickly. The CC28 DA additionally
activates the display illumination, the LED bar and the buzzer, alternating in high frequency. The
display also flashes
----
(also refer to Exceeding Detection Range).
On principal the ambiguity alarm is latching and can only be reset by pressing key
QUIT
MENU
(or by
pressing the AutoZero key at models without display). The measurement value must be within the
detection range.
!
The transmitter cannot recognize when the danger of an explosive gas
mixture resp. of an even higher gas concentration has ended. The end of a
gas hazard has to be checked with a portable detector which was already
turned on outside the hazardous area.
Should such an alarm be triggered by a high gas concentration, make sure to check ther zeropoint and
the sensitivity of the sensor, once the alarm was reset. Take into consideration that zeropoint and
sensitivity may vary considerably during the first few days.
Sensor Life
Catalytic combustion sensors are subject to a limited lifetime. The expected lifetime of the sensor
used in the CC28 for combustible gases is approx. 3 to 5 years, depending on operational conditions.
A few months before the lifetime expires, the transmitter indicates that the sensor has to be replaced
with the next service. The message is indicated by the fault LED flashing regularly and by the the
alternating reading of CHNLM SENS and the measurement value. If the sensor is not being replaced
within the next few months, the transmitter turns off the detection mode, when the sensor is
exhausted. The current interface provides an output of 1.2 mA, the yellow fault LED lights up and
the green operational LED shortly flashes in intervals.
Fault