Detcon 880S-N1R - Manual (Page 6)

880-N1R
880-N1R Instruction Manual Rev. 0.0 Page 2 of 38
1.2 Analog Systems (4-20mA sensors)
The signal outputs from multiple sensors provide the user with various options for integrating the Model 880
Graphic Control System. One method of integration is accomplished by using 4-20mA signal output gas
sensors with Detcon DA4 Modules (Figure 2). The DA4 Module receives an analog 4-20mA signal
corresponding to the range of detection then changes it to Modbus™ before relaying the information to the
880A. The Sensor’s output signal is calibrated so that a 4mA input represents a reading of “0” and a 20mA
input represents a reading of full scale. The scale used for each sensor is user programmable and can be set in
the field. Readings outside the range of 4-20mA will cause a Fault.
4-20mA
INPUT
COMM
M
S
D
L
S
D
Typical Sensors
Sensor 2
Sensor 1
Sensor 3
Sensor 4
Figure 2 DA4 4-20mA Configuration
Analog 4-20mA networks are typically recognized as the most fail-safe approach. When using DA4
Module(s), the 880A can communicate with up to 72 analog input channels.