VersaPro Temperature Controller
Page 43
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14
Scaling Analog Inputs
If either input is set to Linear mode the displayed value for that input can be scaled any desired engineering
unit. This is helpful if the measured linear value has to be scaled and re-transmitted on one of two analog
output channels.
Using the equation y = mx + b, where
Y is the desired engineering unit to be displayed
X is the linear millivolt value
M is the Slope of the y/x relationship
B is the y intercept
14.1 Linear
Example
Let us use Input A as an input for an oxygen transmitter that linearizes the percent oxygen to a 0mV to 53.2mV
signal for a 0% to 100% oxygen range. Since both the signal output and the process minimum are both 0, the
Input A offset will be 0.
The slope can be calculated by dividing the maximum process value (100) by the maximum input level
(53.2mV). This gives a slope value of 1.879. This number can be entered as the Input A slope. The decimal
point can be shifted by placing the flashing cursor on the most significant digit and pressing the Left arrow key
until decimal point shifts to the required position.
These scaling values will produce a process value of 100.0160% oxygen for a maximum sensor input of
53.2mV. The process display can be configured to display either 100 or 100.0. This process value can then
be retransmitted to other control devices are a recorder. The control model of the Versapro will be able to
control to a setpoint for the new process value.
14.2 Keyboard Function during Input Slope
The four digits in the slope display can be change from 0 to 9 or the left digit and change to the negative sign.
This most significant digit position also allows you to shift the decimal point by pressing the LEFT arrow key.
The decimal point will shift from first digit to the third digit as the LEFT arrow key is pressed. Pressing the
RIGHT arrow key when the cursor is on the least significant digit will shift the decimal point to the right.