Laurel Electronics Laureate Digital Panel Meter for Process, Strain & Potentiometer Follower Signals - Manual (Page 4)

LAUREL ELECTRONICS INC., 3183-G Airway Ave., Costa Mesa, CA 92626, USA • Tel 714-434-6131 • www.laurels.com 4
Application Examples
Potentiometer Application
In potentiometric (or potentiometer follower) applications, the
signal from a sliding contact voltage divider can be converted to
engineering units such as position, level or percentage. By ope-
rating in a ratiometric mode, the meter will remove any effects
caused by variations in the excitation supply. For use with a 1 kohm potentiometer, the recommended applied
excitation voltage is 10 V, and a 2 kohm resistor should be
placed in series with the excitation output and excitation return
leads. This will allow the meter's 2.0000 V scale with a high input
impedance of 1 Gohm to be used.
Powering two-wire transmitters
Testing with peak detection
The isolated 24 Vdc, 50 mA excitation output, which is standard
with all Laureate meters, is ideal for powering two-wire, 4-20 mA
transmitters. The same two wires are used to apply voltage and
carry the output current. Inside the meter, the 4-20 mA current is
dropped across a 10 ohm resistor and sets up a 40-200 mV volt-
age, which is then sensed by the meter and scaled to engineering
units. Destructive testing is an ideal application for the Laureate strain
meter. Peak readings are automatically captured at rates up to
60 per second, while the display updates at a legible 3.5 read-
ings per second. The peak reading can be recalled at the push
of a button or be transmitted via RS-232 or RS-485. The meter
provides isolated 10 Vdc power for up to four (4) the strain
gauges and can be scaled to read out directly in engineering
units from -99,999 to +99,999.
Custom curve linearization Rate from successive readings
The Laureate DC meter with the Extended main board option
allows exceptionally accurate custom curve linearization. For
setup, up to 180 data points can be entered into a spreadsheet.
The system then creates multiple non-linear spline-fit segments,
which provide much better accuracy than linear segments.
Illustrated, is the readout of volume of irregularly shaped tanks
based on measured liquid level or pressure. Altimeters and
thermistors are further applications. The Extended computer board allows the display of rate based
on successive readings, for instance flow rate based on changes
in liquid level or static pressure in a tank. In the above illustration,
the meter displays the rate in gallons at which a horizontal tank
is being emptied. The input to the meter can be nonlinear, since
only the linearized readings are compared for the determination
of rate.