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Replacing Corrosion Sensors
When a corrosion sensor reaches its end of life, which happens when it reaches 4000 Angstroms of corrosion
accumulation, it will cease to function and must be replaced. When a replacement sensor is obtained, install it on the
OnGuard in the same place as the sensor that failed. The upper sensor location is for Copper sensors and the lower
position is for Silver sensors. The OnGuard will recognize that a new sensor has been installed and will begin the
initialization procedure
. The LCD will display a message indicating that the initialization sequence is in process. This
process takes two hours, and during this time the information received from the OnGuard for that sensor is not valid.
When the initialization sequence is complete the LCD message will be replaced with valid sensor readings.
Current Outputs from Channels
The OnGuard has five 4-20mA current outputs that correspond to Copper Cumulative, Silver Cumulative, Temperature,
Relative Humidity and Pressure. The current outputs are accessible in the large 12-pin terminal block on the bottom of
the OnGuard. Pin 1 and Channel 1 is located on the left end of the terminal block as viewed from the front. There is no
LCD screen on the OnGuard that deals with the Current Outputs. These outputs are disabled when the OnGuard is
battery operated.
Channel 1, Copper Cumulative, Pin 1 (-), Pin 2 (+), 4-20mA = 0-4000 Angstroms Channel
2, Silver Cumulative, Pin 3 (-), Pin 4 (+), 4-20mA = 0-4000 Angstroms Channel 3,
Temperature, Pin 5 (-), Pin 6 (+), 4-20mA = 0-100C
Channel 4, Relative Humidity, Pin 7 (-), Pin 8 (+), 4-20mA = 0-100%
Channel 5, Pressure, Pin 9(-), Pin 10 (+), 4-20 mA = 0-0.4 IWG
OnGuard External Power, Negative Input, Pin 11
OnGuard External Power (+12-36VDC), Positive Input, Pin 12
