Spectrex Series 300 Open-Path Gas Detection System - Manual (Page 19)

Spectrex Inc. - SafEye TM 300 Gas Detector Manual – TM 794100, Rev. D, May 2004
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Table 4. Standard (default) 4-20mA Current for the Gas Channel
Current Status and Description
0mA +0.5mA Fault 2 or Low Voltage
2mA ±0.5mA Fault 1
4mA ±0.5mA Zero reading - No gas detected
4-20mA Continuous measuring of gas concentration at a range
between 0 and 5 LEL.m or full scale
21mA Concentration is over the range limit (more than full scale
concentration).
Table 5. Discrete reading of 4-20mA at different detector’s modes
LEL.m Setting Current Reading Mode
301 302
0 +0.5mA Fault 2 or Low Voltage - -
2 ±0.5mA Fault 1 - -
4 ±0.5mA Standby 0 0
14 ±0.5mA Warning 0.6 1
19 ±0.5mA Alarm 1 2.5
3.7.2 Relays
The detector includes three relays:
•
Fault relay
•
Alarm relay
•
Accessory relay
Fault Relay contacts are normally energized closed, and opened when in Fault
condition
3.7.3 RS-485 Interface
The RS-485 input/output sends complete data information to a PC and receives
data or control commands from the PC. The communication with the PC is
operated through this interface is executed only when used with appropriate host
software.
The following PC minimal hardware requirements are as follows:
•
386 PC using DOS Ver. 5.0 or higher
•
1 MB RAM.
•
2 MB free hard disk space.
•
1.2 or 1.44 MB floppy drive
•
Color VGA
•
RS-485 Interface Card to be defined as COM1 or COM2. Isolated Adapter
is preferred.