Lake Shore Model 331 Temperature Controller User’s Manual
4.14.2 Linear
The Model 331 will process either of two simple linear equations for each sensor input: MX+B or
M(X+B). The result can be displayed or directed to the analog voltage output.
There are two different equations available. In each: M is a gain or slope, X is an input reading, and B
is an offset or intercept (not to be confused with input B). The two equations are shown in Table 4-4.
The difference between them is subtle. The first equation is used to scale the raw reading of an input,
similar to a temperature response curve, when the sensor has linear response. The second is better
at generating a control signal when a setpoint (SP1 or SP2) is selected as B. The control signal can
then be directed to an analog output. The second equation is also useful whenever a reading of
deviation from setpoint is needed.
Table 4-4. Linear Equation Configuration
Equation M X B
M X + B
M (X + B)
Number Sensor
Temp K
Temp C
Number
+SP1
-SP1
+SP2
-SP2
The columns settings in Table 4-4 are selected independently. “Number” represents a number
entered by the user. “X” can be set to an input reading in sensor units or temperature in kelvin or
Celsius. SP1 represents setpoint of Loop 1 and similarly for other B settings.
NOTE: When using the linear equations MX+B or M(X+B), the user should ensure that the
setpoint and “x” variable units match. If the units do not match, the instrument will
continue calculations, but results may not be what is expected.
To configure a linear equation continue from the math setup screen in Paragraph 4.14 and press the
Enter key until the following display appears.
Select for Math A °®
Linear Equ MX+B
Use the s or t key to toggle between the two linear equations: MX+B or M(X+B), where:
M = slope of a line, X = reading data from a sensor input, and B = offset of a line.
Enter for Math A
Lin Equ M +0.0000
The Linear Variable M is entered using the numeric keypad, which includes the numbers 0 – 9, +/–,
and decimal point. Press the
Enter key to accept the new setting. You will see the next display.
Select for Math A °®
X Source Temp K
Use the s or t key to toggle between the Linear X Variable: Temp C, Temp K, Sensor. Press the
Enter key to accept the new setting. You will see the next display.
Select for Math A °®
B Source Value
Operation 4-27
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