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20. CUSTOM CURVE LINEARIZATION
Curve.exe is a DOS-based, executable PC program used to set up an Extended meter so that
the readings have a user-defined, non-linear relationship with the input signal. The calculated
linearizing parameters are downloaded into non-volatile memory of the meter. For example, it
allows a meter to correct for transducer nonlinearity or to display volume of an irregularly
shaped tank based on pressure mea-
sured at the bottom of the tank. The
curve-fitting algorithm uses quadratic
segments of varying length and curva-
ture, and provides diagnostics to esti-
mate curve fitting errors. The program is
self-prompting, avoiding the need for a
detailed printed manual. This manual
section is only intended as an intro-
duction.
PREREQUISITES
1) PC-compatible computer with an available USB or RS232 communications port.
2) Extended DPM-3 meter.
3) A USB or RS232 board in the meter. This board can be used for meter setup only, then
be removed.
4) USB cable, A to B, or RS232 cable, RJ11-to-DB9 (P/N DPM-3-RJ11AD9), to connect
the meter and PC.
5) Curve.exe software, available from Transducer Techniques.
GETTING STARTED
Download curve.exe into the same directory that will contain your data files, such as
c:\curves. Set the meter baud rate to 9600. To do so, press the key to get to SEr 1, then
set the entry to __050. Set the meter address to 1. To do so, press the key to get to SEr
2, then set the entry to _0011. To execute the program from Windows, simply double-click
on curve.exe, which is an executable file. Follow the steps on computer screens, which will
prompt you and provide extensive information. Pressing R (Enter) returns to the main menu.
You will be given the choice to enter your data in one of four modes:
1) Text file entry mode, with an X value in one column and a Y value in another. There
can be additional columns, which are ignored. The file must have a DOS name of up to
8 characters and the extension .RAW. There can be from 5 to 180 rows. X is the input
value and should be in the unit of measure for which the meter was set up, such as mV
or V. Y is the desired corresponding reading, and can range from -99999 to 99999 with
any decimal point.
2) 2-coordinate keyboard entry mode, where an actual X input signal is applied, and the
desired Y reading is entered from the keyboard.
3) 2-coordinate file entry mode, where an actual X input signal is applied, and the
desired Y reading is provided from a file.
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