10
“One Point” Calibration
The “One point” calibration allows the user to offset the output of the RTD
Transmitter to match perfectly a known temperature to which the RTD Transmitter is
set.
To perform this calibration, a known and stable temperature reference is required.
Set the RTD Transmitter to this known reference temperature and wait long enough
to be sure that the reading is stabled. To establish what the output current should
be
at this reference temperature, the user can enter the value of the reference
temperature (in the current engineering units) in the corresponding text box (“For a
Temperature of “) located in the “1 POINT CALIBRATION” section of the
“Programming” window.
The theoretical output current will then be automatically calculated and displayed in
the corresponding text box (“theoretical output should be “). If the current indicated
by the loop c
urrent indicator does not match the theoretical value, then click on the
“+” or “-” button of the “Adjustment” section to adjust the output reading to the
correct value. Every time the “+” or “-” buttons are clicked, the new value is
uploaded and saved in the RTD Transmitter memory.
NOTE:
The “Actual Reading” section located on the bottom right section of the
Programming window displays values calculated by the 920_Prog Txr
program. This ca
lculation is based on the digital reading (via the USB)
and may not correspond exactly to the current output read by the loop
indicator. For better accuracy, use the reading from a calibrated loop
indicator to make the adjustments.
“Two Point” Calibration
The “Two point” calibration allows the user to calibrate the RTD Transmitter against
two known reference temperatures in the operation range. This calibration is
performed
in three steps.
The first step is the “First Point” reading. The RTD Transmitter has to be set at a
known and stable reference temperature inside its operating range. The first point
must be at a lower value then the “Second Point”. Once the output reading from the
RTD Transmitter is stable, enter the temperature value in the text box called “First
Point:” located in the 2 POINTS CALIBRATION section, and click on the
co
rres
ponding “Read” button. The input value is then saved in the RTD Transmitter
memory as well as the temperature reference for the first point.
The second step is the “Second Point” reading. The RTD Transmitter has to be set
at a known and stable reference temperature inside its operating range. The second
User’s Manual – Preliminary Version
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