If it is desired to trim the digital level value, he may select a single point zero trim or a full level trim that requires the input of both the zero level value and some other level value preferably near the end of the level measurement tube.
If the transmitter is configured with temperature measurement, he may select a single temperature trim point at 0 deg C or a full temperature trim that requires trimming both at 0 deg C and some other temperature point near the upper end of the operating temperature range.
Output Current (DAC) Calibration
If the user selects Scaled D/A trim from the Calibration screen, this screen will appear reminding the user that the loop should be removed from automatic control before proceeding. When this has been done, the user must press OK to continue.
The next screen informs the user that the rest of the procedure will use the values 4.000 to 20.000 in the instructions if you are using a milliamp meter. If you are using a voltmeter across a resistor, select change and provide the values that you will be using at the current end points. The user must press ENTER when ready.
The HART Communicator now instructs the user to connect the reference meter that is to be used for the current calibration. The user must press OK when ready.
The HART Communicator will now command the transmitter to set the current output to 4.000mA. The user must press OK when ready
to have the current output set to 4.000mA.
When the device has set the current output to 4.000mA, the user is to enter the reference meter reading. For example, if the meter actually reads 4.234mA, that value is input with the keypad. The user must press ENTER when the current value has been entered.
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The transmitter, based on the data from the reference meter, will calculate a new value for the DAC zero calibration constant and change the output current based on the new constant. If the current read by the reference meter is now 4.000mA, the user must press ENTER. If not exact, the user must select No and press ENTER to try again.
The HART Communicator will now command the transmitter to set the current output to 20.000mA. The user must press OK when ready
to have the current output set to 20.000mA.
When the device has set the current output to 20.000mA, the user is to enter the reference meter reading. For example, if the meter actually reads 19.975mA, that value is input with the keypad. The user must press ENTER when ready to proceed
The transmitter, based on the data from the reference meter, will calculate a new value for the DAC gain calibration constant and change the output current based on the new constant. If the current read by the reference meter is now 20.000mA, the user must press ENTER. If not exact, the user must select No and press ENTER to try again.
The Current Output calibration is now complete. The HART Communicator will now return the current output of the transmitter to normal operation.
The user is then notified that the loop may now be returned to automatic control. After the user presses OK the HART Communicator returns to the Calibration screen.
The HART Communicator is now at the starting screen for the Scaled D/A trim.
