Rosemount 8712, Reference Manual

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Reference Manual
00809-0100-4664, Rev BA
January 2010
4-19
Rosemount 8712
Loop Test
The loop test allows you to drive the transmitter output to a desired electrical
current output on terminals 1 and 2. This capability allows you to check the
entire current loop prior to start-up. On the LOI the test will end after five
minutes if the transmitter is not returned to normal operation manually.
D/A Trim
The D/A Trim is used to calibrate the 4-20 mA analog loop output from the
transmitter. For maximum accuracy, the analog output should be trimmed for
your system loop. Use the following steps to complete the Output Trim
function.
1. Set the loop to manual, if necessary.
2. Connect a precision ammeter in the 4–20 mA loop.
3. Initiate the Output Trim function with the LOI or Handheld
Communicator.
4. Enter the 4 mA meter value when prompted to do so.
5. Enter the 20 mA meter value when prompted to do so.
6. Return the loop to automatic control, if necessary.
The 4–20 mA trim is now completed. You may repeat the 4–20 mA trim to
check the results, or use the analog output test.
Scaled D/A Trim
Scaled D/A trim enables you to calibrate the flowmeter analog output using a
different scale than the standard 4-20 mA output scale. Non-scaled D/A
trimming (described above), is typically performed using an ammeter where
calibration values are entered in units of milliamperes. Scaled D/A trimming
allows you to trim the flowmeter using a scale that may be more convenient
based upon your method of measurement.
For example, it may be more convenient for you to make current
measurements by direct voltage readings across the loop resistor. If your loop
resistor is 500 ohms, and you want to calibrate the meter using voltage
measurements made across this resistor, you could rescale your trim points
from 4-20mA to 4-20mA x 500 ohm or 2-10 VDC. Once your scaled trim
points have been entered as 2 and 10, you can calibrate your flowmeter by
entering voltage measurements directly from the voltmeter.
Field Comm. 1, 4, 2, 1, 5
LOI Key AUX. FUNCTION
Field Comm. 1, 4, 2, 1, 6
LOI Key AUX. FUNCTION
Field Comm. 1, 4, 2, 1, 7
LOI Key AUX. FUNCTION