H Comm Module Operation - Signet 9900 Operating Instructions Manual

H COMM Module Operation

Loop Powered systems require a minimum of 24 VDC. If connecting with DC, nominal 12 VDC is acceptable.
(See Power Wiring, pg. 17)
• In LVL/VOL mode, the primary variable will always represent Level, the secondary variable will always
represent Volume.
• In pH, Conductivity, Resistivity and Salinity systems the secondary variable represents Temperature.
• In Flow, the secondary variable represents the Totalizer. Select Permanent or Resettable Totalizer in the
Input menu (pg. 32).
Loop Current Trim Procedure
The Loop Current HART commands allow a Master HART device to update a loop current value in the 9900
Transmitter and to perform a two-point calibration (zero and span) of the loop current.
1. Use Command 40 (Enter/Exit Fixed Current Mode) to update the 4.00 mA current.
2. Using the measured value of your reference instrument (either a digital multimeter or the HART Master device),
set the zero trim using Command 45 (Trim Loop Current Zero). The transmitter will then trim its calibration and
return the loop current value in the response message. The response value may differ slightly from the value
sent by the Master due to rounding.
3. Use Command 40 (Enter/Exit Fixed Current Mode) to update the 20.00 mA current.
4. Using the measured value of your reference instrument (either a digital multimeter or the HART master device),
set the span trim using Command 46 (Trim Loop Current Gain). The transmitter will then trim its calibration and
return the loop current value in the response message. The response value may differ slightly from the value
sent by the Master due to rounding.
5. Repeat steps 1 through 4 as needed to gain the accuracy desired. Once the loop current is calibrated to your
satisfaction, return the device to normal operation by issuing Command 40 (Enter/Exit Fixed Current Mode)
with a value of 0.0. This will take the 9900 out of fi xed current mode.
Note: With the H COMM Module installed, the following functions are not accessible via the 9900 keypad:
• Trim Loop Current
• Test Loop Current
These functions are only accessible via the HART interface.
Changes to Units of Measure in Transmitter
HART devices can be used to change the units of measure in a 9900 Transmitter. After an update, you must
cycle power to the 9900 Transmitter (remove power for 5 seconds, then restore power). In a fl ow system,
the units update automatically and it is not necessary to cycle power to the 9900 Transmitter.
9900 Transmitter 67