2-11
EN
NOTE
Select pressure input values so that the low and high values are equal to or outside
the 4 and 20 mA points. Do not attempt to obtain reverse output by reversing the
high and low points. The transmitter allows approximately a 5% URL deviation from
the characterized curve established at the factory.
3. Follow the commands provided by the communicator to complete the
adjustment of the lower value.
4. Repeat the procedure for the upper value, replacing
2 Lower sensor
trim with
3 Upper sensor trim
in Step 2.
Output Trim
The output trim commands allow you to alter the transmitter’s conversion of the
input signal to a 4–20 mA output (see Figure 2-3 on page 2-9). Adjust the analog
output signal at regular intervals to maintain measurement precision. Match the
transmitter output to the output of the digital readout device (ammeter, DCS, etc.).
You can trim the transmitter output using either the digital to analog trim or the
scaled digital to analog trim function.
Digital to Analog Trim
To perform a digital-to-analog trim, perform the following procedure.
1. From the HOME screen, select
1 Device setup
,
2 Diag/Service
,
3 Calibration
,
4
D/A trim
. Select “OK” to after you set the control loop to manual.
2. Connect an accurate reference meter to the transmitter at the “Connect
reference meter” prompt. To do so, connect the meter across the test terminals
in the transmitter terminal compartment, or use the readout device within the
loop.
3. Select “OK” after connecting the reference meter.
4. Select “OK” at the “Setting fld dev output to 4 mA” prompt.
The transmitter outputs 4.00 mA.
5. Record the actual value from the reference meter, and enter it at the “Enter
meter value” prompt.
The communicator prompts you to verify whether or not the output value equals the
value on the reference meter.
6. Select
1 Yes
if the reference meter value equals the transmitter output value,
or
2 No
if it does not.
If you select
1 Yes
, proceed to Step 7.
If you select
2 No
, repeat Step 5.
HART Comm.
1, 2, 3, 2, 1
1
4690.bk : 4690.s2 Page 11 Tuesday, May 26, 1998 5:28 PM
