Customer Service 800-528-7411 or 602-470-1414
Page 55 of 68
16 4-20 MILLIAMP AND SIGNAL RELAY CONNECTIONS
The 651 provides both a 4-20 mA connection and a signal relay connection on the
circuit board. Remove the two screws securing the Circuit Board Cover to access these
connections on the circuit board.
Once the desired connections have been implemented, replace the Circuit Board Cover
and two screws.
16.1 4-20 mA
The 4-20 mA connection can be used to indicate the H
2
S reading level on a proportional
scale from 4-20 milliamps for connection to certain industrial systems, such as SCADA.
A 4 mA current level always corresponds to an H
2
S reading of 0.000 ppm. The 20 mA
level can be set as high as the maximum reading level for the 651 (50 ppm) or
somewhere between 0.000 and 50 ppm, depending on your application.
SIGNAL RELAY
4 TO 20 mA
