MSR ELECTRONIC PolyGard 2 MC2 - 2 Functional Description; General; Measuring Mode; Special Mode

User Manual PolyGard
®
2 Sensors 2023-11 Page 7 | 40
2 Functional Description
2.1 General
The Sensor includes electronics with a measuring amplifier and µController for processing the meas-
ured values in addition to the gas sensor element. All relevant data and measured values of the sen-
sor element are stored in a fail-safe way in the internal memory of the µController and are transmit-
ted digitally to the Board of the SC2 via the MSR local bus.
The SC2 Sensor is connected to SB2, MSC2, MSB2 or WSB2 Board via the digital interface.
The MC2 Sensor provides an analog output signal of 4–20 mA (2–10 V as an option), which means it
can also be used without the Boards of the PolyGard
®
2 series.
2.2 Measuring Mode
See user manual of the SB2, MSC2, MSB2 or WSB2 Boards.
2.3 Special Mode
See user manual of the SB2, MSC2, MSB2 or WSB2 Boards.
2.4 Sensor Element
A: Catalytic Sensor Element (Pellistor) for Combustible Gases
The integrated sensor works according to the catalytic bead principle. The ambient air to be moni-
tored diffuses through the opening on the sensor head into the measuring chamber of the sensor.
Here the combustible gases and vapours are catalytically burned at a heated detector (Pellistor). The
resulting combustion heat additionally heats up the detector. This heating results in a change in the
resistance of the detector. It is proportional to the concentration of the combustible gases.
In addition to the catalytically active detector, the sensor also contains a heated, inactive compen-
sator. Both components are part of a Wheatstone measuring bridge. Environmental influences such
as temperature or humidity of the ambient air to be monitored affect both components to the same
extent, whereby the influences on the measurement signal are almost completely compensated.
The ageing process is accelerated by the high temperatures that occur during the combustion of the
measuring gas. Therefore, zero point and the gain must be calibrated at regular intervals.
For testing the sensor, do not use a lighter for gassing. The sensor is then unusable for measurement.
The MSR warranty expires if the sensor is gassed with a lighter.