Detcon 700 HRT Bridge - Manual (Page 17)

HRT Bridge
700 Sensor HRT Bridge IM Rev. 0.2 Page 13 of 18
NOTE 2: If the sensor fails the stability criteria, a “Stability Fault” will be declared and a “Fault
Detected” message will be displayed alternately on the sensor with the current reading. The HART
Sensor Status will change to reflect a Sensor Fault.
NOTE 3: If the sensor fails the clearing time criteria, a “Clearing Fault” will be declared and a “Fault
Detected” message will be displayed alternately on the sensor with the current reading. The HART
Sensor Status will change to reflect a Clearing Fault.
4.3.2.2 Loop Test Calibrate
The Calibration Screen contains a Loop Test Calibration section. This section displays the loop current
reading and allows the user to perform D/A trim and Loop Test. D/A trim is used to calibrate the 4mA and
20mA set points in the Digital/Analog converter. Loop test allows the user to set the mA output to any level
within range; this can be a good troubleshooting tool for line degradation. A DVM capable of reading
milliamps and a 100~250 Ohm resistor are required to perform D/A trim and/or Loop test.
HRT BRIDGE
SENSOR
+24V
mA/HART
mA/HART
GND
+24V
CFG
HART
HART
+ 24V
100~250 Ohm Resistor
DVM +mA
GND (- 24V)
DVM GND
HART
Connector
HART
Header
HRT Bridge PCA
Figure 8 DVM Connection
D/A Trim
1) Select “D/A trim” from the Loop test Calibrate section of the screen.
2) The procedure will prompt to connect a meter: (Refer to Figure 8.)
a) Disconnect the wire from the HART Connectors mA/HART position.
b) Connect one end of a 100~250Ohm resistor to the mA/HART position of the HART Connector.
c) Connect the positive lead of a DVM set to measure milliamps to the other end of the resistor.
d) Connect the negative lead (-) of the DVM to the GND position of the connector.
3) The procedure will set the output to 4ma, and prompt for the DVM Reading. Input the reading and select
“OK”.
4) The HRT Bridge will readjust the output for 4mA, and inquire if the reading is 4mA on the DVM (select
“YES” or “NO”).
5) If the reading on the DVM is 4mA, select “YES” and “OK” and the HRT Bridge will continue on to
20mA. If the reading is not 4mA, select “NO” and “OK” and the procedure will re-run the 4mA
calibration (Step 3).
6) The procedure will set the output to 20mA, and prompt for the DVM Reading. Input the reading and
select “OK”.
7) The HRT Bridge will readjust the output for 20mA, and inquire if the reading is 20mA on the DVM
(select “YES” or “NO”).
8) If the reading on the DVM is 20mA, Select “YES” and “OK”. If the reading is not 20mA, select “NO”
and “OK” and the procedure will re-run the 20mA calibration (Step 6).