Atest Gaz SmArtGas 4, Руководство пользователя

Страница: 14 / 48

www.atestgaz.pl
4.2 RS-485
Communication via the RS-485 employs either the Modbus ASCII or the Sigma Bus protocol (when the
detector is used with other devices of the Sigma system).
For detectors with the RS-485 outputs the output signal has a digital form (see appendix [4]). In general, the
detector status is specified by means of the following variables:
Measurement results expressed as percentage of the full range.
Information about exceeding of alarm thresholds.
Status information with indication of possible failures or defects, etc.
4.3 Current output
4.3.1 Operating mode – current flow direction
The current output can be in two operating modes: sink or source. The method of connecting the detector
for both modes is shown below.
Figure 7: The way of connecting the detector depending on the direction of current flow
Information about maximum valuels U
s
and R
obc
you can find in Table 10.
Details about configuration – see Section 6.4.1.
4.3.2 Operation mode – coding information
The current signal may be proportional to the concentration of the gas detected (continuous output signal).
The signal values are given in the table below.
Current output Status
2 mA Critical failure
From 4 mA to 20 mA
Value corresponding to the measured gas concentration:
4 mA – 0% of range
20 mA – 100% of range
22 mA Gas overloading
Table 6: Continuous output signal
p
. 14|28
User Manual: POD-061-ENG R03
-
+
S
A
Source
-
+
S
A
Sink
R
OBC
U
S