110
Chapter 7
535-PROF User's Manual
Applications
5th
1st
10th
15th
1st
5th
10th
15th
PV VALUE
in engineering units
INPUT VALUE
in milliamps or voltage
Figure 7.18
15-point Linearization Curve
Hardware Configuration
•
A voltage or milliamp input must be installed on the controller.
Software Configuration
1. Go to the
PV1 INPUT
menu.
2. Set
LINEARIZE
to SQR. ROOT.
Custom Linearization
Custom linearization allows virtually any nonlinear signal to be linearized using
a 15-point straight line approximation curve (see Figure 7.18). Typical applications
are linearizing signals from nonlinear transducers, or controlling volume based
on level readings for irregularly-shaped vessels. To define the function, enter
data point pairs—the engineering units corresponding to a particular voltage or
current input.
Software Configuration
1. Go to the
PV1 INPUT
menu.
2. Set the parameter
LINEARIZE
to CUSTOM.
3. Go to the
CUST. LINR.
menu.
4. Enter values for the
1ST INPUT
and
1ST PV
data points. All the input
parameters define the actual milliamp or voltage input. All the PV parameters
define the corresponding process variable value in engineering units.
Figure 7.17
Square Root Linearization Formula
PV = Low Range +
[
(Hi Range – Low Range) (V
input
- V
low
/ (V
high
– V
low
)
]
Hi Range
is the high end of the process variable.
Low Range
is the low end of the process variable.
V
input
is the actual voltage or current value of the input.
V
high
is the high end of the input signal range (e.g. 5 volts or 20 mA).
V
low
is the low end of the input signal range (e.g. 1 volt or 4 mA).
Example
:
PV range is 0 – 1000.
Input signal range is 1–5 volts.
Input signal is 3 volts.
Therefore PV = 0 +
[
(1000 – 0) (3-1) / (5–1)
]
= 1000 .5 =
707
