Series A12
Unisens
2-Wire Transmitter
O & M Manual
- 20 -
Rev-L, 7/15
When the test sequence is activated, the 4-20 mA output will be locked at the value
being transmitted before the sequence began, normally close to 4.0 mA. If you observe the
LCD, you will see the gas concentration begin to increase as gas is evolved from the generator. When
the display reaches 10% above the start value, a PASS message will flash on the display, indicating that
the sensor passed the test. At this point the AUTO TEST flag will stop flashing and go to steady on. This
indicates that the Auto-Test was successful but that the 4-20 mA output is still locked. The output will
stay locked for the next 2 minutes to allow the sensor to recover to zero. In addition, it will remain partially
locked for an additional 8 minutes to insure complete sensor recovery before again activating the output.
However, if the measured gas concentration goes above 50% of range during the second 8 minute inhibit
period, the output lock is released and any receivers connected to the transmitter will indicate high gas
levels.
ANALOG OUTPUT SIMULATION
The
UniSens
transmitter provides the ability to simulate 4 different current output values in order to
verify complete loop integrity and to calibrate receiving devices. The output may be set to values of 4.0, 12.0,
and 20.0, and may also be set to the "Trouble" value below 3.7 mA.
From the NORMAL display, activate the MODE control twice and the display will read "tESt".
Activate the ENTER control. If a sensing module with Auto-Test generator is installed, the display will
change to "SEnS" and the TEST flag will be displayed near the top of the display. Activate the MODE
control once and the display will change to tESt and the mA flag will be on. Activate the ENTER control
once and the display will indicate 4 mA. The current output from the transmitter will now be locked on 4
mA. Use the UP or DOWN control to change the output to 12 mA, 20 mA, or "trbl" as desired. When
"trbl" is displayed, the output will go below 3.7 mA, which is the output value used to indicate "Trouble"
with the transmitter. The output current from the transmitter will change to the value shown on the
display.
CAUTION: Simulation of 12 or 20 mA outputs may cause receiving devices to activate alarms
and/or control devices. Never simulate these outputs without inhibiting alarm receivers
or notifying operating personnel that a system test is in progress.
To escape the output simulation mode, activate the ENTER control once.
