ENGLISH
Pag. 19
1. Introduction
These security instructions refer to the installation, use and maintenance of SMART S-IS gas
detectors series (identification code ST/../EL/..), for applications in areas with presence of
potentially explosive atmospheres.
1.1 General description
Gas detectors series SMART S-IS are devices complete with sensor, housing and interface
circuit, that can be connected to both analogue and addressable control panels as well as
with the MU+.
SMART S-IS gas detectors are intrinsically safe, ATEX and IECEx certified and internally
equipped with a Zener barrier and galvanic separation circuit.
SMART S-IS detectors are used to detect the presence of toxic gases in ppm by means of
an electrochemical cell. The electrochemical cell is extremely reliable and it has the best
performances in detection of gases at low concentration. For this reason it is usually used in
detection of toxic gas.
SMART S-IS gas detectors have a serial RS485 output, an analogue 4-20 ma output and can
be equipped with a 3 relay board. It is equipped with an LCD or LED display. The use of the
display is shown in the display manual.
To protect and increase the stability and accuracy of the gas detector, the microprocessor
present on the internal electric circuit board, is programmed with the following software
algorithms:
³
Self diagnostic procedure to control the detector main operational parts, both hard-
ware and sensing element.
³
Zero point tracking to maintain the zero parameter of the sensor apart from possible
drifts due to thermal or physical variations of the sensor.
³
Digital filter employed in the digital analysis of the analogue values sampled. It is de-
signed to prevent the effects of transients, which may cause instability or incorrect
readings with possible false alarms.
³
Hysteresis cycle applied to the digital outputs to eliminate continuous switching close
to the preset alarm thresholds.
³
Watch-dog for the microprocessor control. In case of intervention, the output current
drops down to 0mA while the red LED stops blinking and remains on. If the RS485 in-
terface is connected, the communication will be interrupted, while if the 3-relay card is
plugged in, the Fault relay will activate.
Summary of Contents for SMART S-IS
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