VPT10-H
HART
®
PRESSURE TRANSMITTER
INSTALLATION, OPERATION, CONFIGURATION AND MAINTENANCE MANUAL
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3.7.
CALIBRATION
VPT10-H allows user to calibrate several variables, according to their own measurement standards, to perfectly fit the
process. Following are the variables that can be calibrated, with their respective procedures.
PRESSURE
It allows the user to adjust the maximum and minimum values to be used in the process, according to the reference
value of the pressure generator used in the calibration. By applying the lower pressure value, user must perform the
lower pressure trim (or zero trim if wishes to calibrate zero pressure). Subsequently, by applying the upper pressure
value, user must perform the upper pressure trim.
ATTENTION
For pressure calibration, minimum span (difference between upper and lower pressure according to
sensor range) must be respected. Otherwise, transmitter will not accept the new calibration values,
maintaining the previous calibration.
With these two calibrations, transmitter starts to have its pressure references for the measurement with maximum
precision offered. The pressure value in percent (%) will be calculated using the user-configured work range in the
parameters previously described in section 3.6.
CURRENT
Current calibration is common for all transmitters and
also for the HART
®
protocol, which provides standard
commands and routines for this functionality.
Generally, configuration and calibration softwares
provide methods that automatically set the output
current to 4 mA and 20 mA according to the calibration
point to be executed (zero or span, respectively).
After generating the fixed current through the
transmitter, with an ammeter connected in series (see
figure 3.12), user can check the actual current
generated and send it by means of HART
®
commands
to the equipment, which will perform the internal
calibration and generate the corrected current, allowing
user to verify the new current in the connected
ammeter, automatically. This process can be repeated
as many times as user deems necessary, until current
is perfectly calibrated at both ends (4 mA and 20 mA).
Figure 3.12 –Mounting for current trim on VPT10-H.
TEMPERATURE
The temperature calibration is the simplest offered by the transmitter, where user only sends the value of the ambient
temperature measured by an external thermometer. The transmitter automatically adjusts the internal temperature
measurement based on the value sent by the user. This process can be repeated as many times as user deems
necessary, until the temperature is perfectly calibrated.