Laurel Electronics Laureate Meters with Custom Curve Linearization - Manual

LAUREL ELECTRONICS INC., 3183-G Airway Ave., Costa Mesa, CA 92626, USA • Tel 714-434-6131 • www.laurels.com 1
LAUREL
ELECTRONICS, INC.
Laureate™ Meters with
Custom Curve Linearization
Key Features of Meter Linearizing
• Applicable to Laureate™ process, strain gauge, load cell meters, frequency /
rate meters, and totalizers
• Easy programming using custom nonlinear curve fits
• Improves accuracy of low-cost transducers
• Extends transducer operating range on high and low ends
• Solves application problems involving non-linear relationships
• Included with Extended versions of Laureate digital panel meters, counters
and timers
• Easy setup by entering data points into a computer spreadsheet, or typing in
desired readings for actual signal inputs.
• Exceptional accuracy from 0.1% to 0.01% of full scale with few data points,
made possible by curvilinear spline fits.
Description
Custom curve linearization is a feature available with the
Extended option version of all Laureate digital panel meters,
counters and timers, excluding only the temperature meter,
which already has built-in linearization curves.
Benefits: Custom curve linearization can provide exceptional
accuracy from low cost transducers of these are repeatable. It
can extend the working range of transducers on their high and
low ends. It can also solve special application problems where
there is a non-linear relationship between the input and the
desired readout.
Implementation: Linearizing is implemented in the form of
20 nonlinear spline-fit segments, which provide much better
accuracy than a larger number of straight line segments. The
typical error will be from 0.1% to 0.01% of full scale, depending
on the number of data points used for setup, the error in the data
points, and the severity of non-linearities or discontinuities.
Easy Setup: Setup of a Laureate Linearizing Process Meter
requires an external PC, which is connected to the meter via
RS232 or USB cable, and utilizes linearizing software furnished
by Laurel Electronics. To download, go to our Software Down-
load web page. A serial communications board is required, but
can be removed from the meter following setup. Three meter
programming methods are offered:
• Spreadsheet Method: Data points consisting of the input
signal in Volts or Amps and the desired reading are entered
into an Excel spreadsheet or into a text file using a space,
comma or tab as the delimiter. There can be up to 180 data
points. Laurel's software then calculates 20 spline-fit seg-
ments and downloads their coefficients into the meter.
• Actual Input Method: The meter is hooked up to the actual
signal source, and the user enters the desired readings for
different signal levels. There can be up to 180 input / reading
combinations. Laurel's software then calculates 20 spline-fit
segments and downloads their coefficients into the meter.
This method automatically compensates for any errors in the
transducer.
• Polynomial Method: The mathematical formula relating the
input to the output is entered into the computer, which then
uses this data to calculate the spline-fit segments. This
method is ideal if the mathematical relationship is knows, for
example to calculate the contents of a tank based on the
known geometry of the tank.
Application Examples
• Thermistors and other sensors whose output is a non-linear
changing resistance.
• Altimeters, since the relationship between pressure and
altitude is non-linear.
• Rate of ascent based on successive altimeter readings.
• Volume of irregularly-shaped tanks, such as horizontal
cylinders, based on measured liquid level or liquid pressure at
the base of the tank.
• Fine-calibration of linear transducers, since even nominally
linear transducers will have nonlinear components.
• Extending the working range of transducers, since many
transducers become nonlinear at their low and high ends.
Compensating for inaccuracy of low-cost transducers.
Measuring tank volume
The Extended Laureate process meter can display the volume of
irregularly shaped tanks based on the static pressure at the base
of the tank. An example is a cylindrical tank lying on its side. The
tank can be tilted to facilitate drainage, as illustrated.