Spectrex Xenon 700 SIL Open-Path Gas Detection System - Manual (Page 29)

TM 799200 Rev (C), January 2014
Output Signals 17
3.2 Output Signals
The SafEye system provides the following outputs depending upon the
wiring option selected (see Models and Types, page 9):
 Standard 0-20mA Current Output, page 18
 Dry Contact Relays, page 18
 RS-485 Interface, page 18
3.2.1 Standard 0-20mA Current Output
The 0-20mA output can provide the Detector status measurement in one of
the two following methods:
 Default - It can be measured proportionally showing a continuous
reading of the exact gas concentration (see Table 1).
 Option - It can be a discrete indication according to the Detector mode
or the warning or alarm signal at a defined gas concentration (see Table
2). Setting of this method can be done by maintenance host or Handheld
unit.
The 0-20mA functions as current sink but can be configured as Source – see
Appendix B.
The maximum permitted load resistance for the 0-20mA output is 600Ω
Table 5: Standard (default) 0-20mA Current for the Gas Channel
Current Reading Status and Description
0mA +0.3mA Fault 2 or Low Voltage (Critical)
1mA ±0.3mA Zero Calibration (In Progress)
2mA ±0.3mA Fault 1 (non-Critical)
3mA ±0.3mA “Maintenance Call”
4mA±0.5mA No gas present
0-20mA Continuous measuring of gas concentration at a
range between 0 and full scale
21mA Concentration is over the range limit (more
than full-scale concentration).