Teledyne LGA-3500 - Laser Gas Analysis system - Manual (Page 75)

Laser Gas Analyzer Alarm Messages
Teledyne Analytical Instruments 61
Alarm Messages
Alarms installed in the Model 3500 include a 3-Channel Relay
Alarm, a 4-20mA output alarm, and LCD display of alarm information.
5.1 Relay Alarm
The 3-Channel Relay in the Model 3500 is set up as follows:
Relay 1—warning alarm relay
Relay 2—error alarm relay
Relay 3—concentration alarm relay
The concentration alarm relay is triggered when the measured gas
concentration has exceeded the high or low limits set by the user. When
this occurs, the relay opens indicating that the current concentration is
out of the set range.
The warning alarm and error alarm when triggered indicate that the
system working status is abnormal (warning status in normal mode and
system error).
Table 5.1 shows the relay and output state for various operational
modes of the model 3500.
5.2 4-20mA Analog Output
When the system status is normal, the 4-20mA analog output
represents the measured gas concentration. In general, 4-20mA
corresponds to the user-defined measurement range. 4mA corresponds
to the minimum value of the user-defined measurement range and 20mA
corresponds to the maximum. When the system encounters an error and
enters error mode, the output of the 4-20mA port is 2mA.
CAUTION: 2MA DOES NOT REPRESENT MEASURED GAS
CONCENTRATION. IT ONLY SHOWS THAT THE
ANALYZER HAS ISSUED AN ERROR ALARM.