30
Smart Temperature Transmitter STT250 – Operator Manual
6.4.2.2 Meter Fault Conditions
The various possible fault conditions with corrective action are:
1. At power up, the LCD stays completely blank. Either the self check failed or the
meter is not receiving power. Check the connections.
Note that the Smart Meter requires 2.25 Volts supply in addition to the minimum
10.8 Volts for the STT250 transmitter (i.e. minimum of 13.05 V across the
meter/transmitter terminals). Verify adequate loop power is available.
2. At power up after showing all LCD segments, the display shows "
BAD XMTR
STATUS
" and "_ _ _" instead of the digital engineering unit display. This means
that the meter received a critical status diagnostic message from the transmitter at
power up. Use the configuration tool to determine the critical status cause and
correct.
3. After successful power up, the display shows "
BAD XMTR STATUS
" and the
bargraph flashes. This means that a critical status condition occurred during
operation. The display value may not be correct. Use the configuration tool to
determine the cause and correct.
4. After successful power up, the display shows "
FAULT-LAST KNOWN VALUE
"
and the bargraph flashes. This means that the on-going self diagnostics of the
meter detected an internal fault or that communications from the transmitter were
lost or that 5 or more corrupted messages were received from the transmitter
operating in the digital output mode. Cycle the power to see if the condition self
clears. If it recurs, check loop wiring for adequate loop power, ensure presence of
the 250 ohm communications resistor and minimize electrical noise in the loop.
5. After successful power up, the display shows "
OUTPUT MODE
" and the bargraph
flashes while the digital display flashes a value 0.0% to 100.0%. This means that
the transmitter went to fixed output mode while operating as a digital output
device. Connect the configuration tool and press "
OUTPUT
", "
CLEAR
" to revert to
normal operation.
6. The display shows "
ANALOG
", "
0.0%
" and no bargraph segments switch on. This
means that the Smart Meter requires calibration to the transmitter operating in
4-20 mA analog output mode. See Section 6.4.3.
6.4.3 4-20 mA Analog Mode Calibration of Smart Meter
Calibration is beneficial to ensure display accuracy with a 4-20 mA
analog signal. It is
unnecessary to recalibrate the meter since all Smart Meters are factory calibrated
before shipment. However, the facility is included in case recalibration for time drift or
transmitter end point offsets are required.
Basically, accurate 4 and 20 mA signals are provided to the meter with the "
CAL
"
configuration button selected. The 4 and 20 mA signals can be conveniently provided
by using the configuration tool to switch the transmitter to "
OUTPUT MODE
".
The full calibration procedure for a Smart Meter is:
•
Step 1
- Put control loop to Manual and use the configuration tool to establish
communications. Put the transmitter into 0% output mode by pressing "
OUTPUT
",
"
0
", "
ENTER
" for "
0.0%
" on SFC.
Summary of Contents for STT25D
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