18. TRANSMITTER CALIBRATION
All analog input and analog output ranges of the transmitter have been digitally calibrated at
the factory prior to shipment using calibration equipment certified to NIST standards.
Calibration constants are stored digitally in non-volatile memory in EEPROM on the signal
conditioner board and main board. This allows signal conditioner boards to be changed without
requiring transmitter recalibration.
If periodic recalibration is required, the transmitter may be returned to the factory or to any
authorized distributor. A modest fee will apply, which also covers a Calibration Certificate.
DC, load cell, AC RMS, and thermocouple signal conditioner boards can be calibrated using
Instrument Setup Software running on a host PC, which is connected to the transmitter via
Ethernet. The Calibration screen of Instrument Setup Software is accessed by clicking on
Calibration at the top of the DPM Main Menu screen. The PC first recognizes the type of board,
then prompts you to apply specific jumpers and specific known signals for each range. Press
Repeat to take more readings. When you have decided on which reading to accept, press on the
number 1 through 10 of that reading.
The RTD/Ohms signal conditioner board cannot be calibrated using the Calibration screen of
Instrument Setup Software. Instead, use the Scaling tab under Setup. Here you can enter
values for Scale and Offset for a specific range. These corrections apply to resistance, not to
RTD temperature. To calibrate RTD temperature, refer to the published resistance table for your
RTD type, and calibrate resistance. For example, if your measured resistances are 0.1% low,
apply a scale factor of 1.01.
19. CUSTOM CURVE LINEARIZATION
Curve.exe is a DOS-based, executable PC program used to set up an Extended transmitter so
that the internal digital readings have a user-defined, non-linear relationship with the input
signal. For example, it allows a transmitter to correct for transducer nonlinearity. Calculated
linearizing parameters are downloaded from a PC into non-volatile memory of the transmitter.
The curve-fitting algorithm uses quadratic segments of varying length and curvature, and
includes diagnostics to estimate curve fitting errors. The program is self-prompting, avoiding
the need for detailed printed instructions.
To get started, download curve.exe from our website into the directory that will also contain
your data files, such as c:\curves. Connect your transmitter to the PC and double-click on
curve.exe, which is an executable file. Follow the computer prompts and extensive help
information. Pressing R (Enter) returns to the main menu. You will be given the choice of four
data entry modes, which are explained in detail: 1) Text file entry mode, 2) 2-coordinate
keyboard entry mode, 3) 2-coordinate file entry mode, and 4) Equation entry mode.
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