Black Box ServSensor JR EME102A, Manual, Page: 42 / 135

40
ServSensor JR
40
to maintain 0 Volts. If Direction is set to Input and the OutputLevel is
set to low, the Switch will become tri-state.
The Output level of High will pull-up the switch even if the Direction
is set to Input. However when the Switch Direction is set to Input and
Output level is set to high the Switch will output a weak pull-up
current. This output can be overridden by shorting the pin to ground. In
this way an external switch can be determined to be open or closed.
NormalState: The Switch NormalState can be either Open/+5 Volts or
Closed/GND. When set to a +5 Volts, the input value of 5 volts will
cause the status to be reported as
“normal” . When set to +5 Volts, the
input value of 0 volts will cause the status to be reported as
“lowCritical” . When the Switch NormalState is set to a Low, the input
value of 5 volts will cause the Status to be reported as “highCritical”
and the input value of 0 volts will cause the status to be reported as
normal.
Information on Dry contact cables
The extension length of the dry contact twisted pairs is limited only by
the amount of electromagnetic noise in the area. So the lengths can be
quite long, but long cable lengths may create occasional false positives.
These false positives can be eliminated with the advanced filtering of
the ServSensor JR. You can define how long a sensor must be in the
error condition before changing state from Normal to Critical. You can
also define how long the sensor must remain in the Normal state before
changing from Critical to Normal.
If the dry contact cable is run outdoors where lighting strikes may
occur or if the cable length is very long we recommend the use of the
ServSensor X20 or the ServSensor X60, which includes integrated
opto-isolators. This will protect the ServSensor X20/X60 in case of a
lightning strike. This is because there is no connection to the power
supply in the ServSensor X20/X60. This is done in order to provide
complete isolation and protection to the ServSensor X20/X60.