5-2
IM WT1801-01EN
Linear Scaling of Analog Input
You can set the slope and the offset value of the auxiliary input using one of the following two methods.
• Set the values manually.
• Specify two points, and use those points to compute the values
Manually Setting the Auxiliary Input Slope and Offset (Linear Scale A, B)
You can set the slope (A) and offset (B) of the auxiliary input to values within the following ranges.
A: 1.000 m to 1.000 M
B: –1.000 M to 1.000 M
The following equation is used to compute measured values of the auxiliary input.
Auxiliary input measured value = S(AX + B) – NULL
S:
The scaling factor
A:
The auxiliary input slope
X:
The input voltage of the auxiliary input
B:
The offset
NULL:
When There Is No Offset in the Auxiliary Input Voltage
If you set A to 1 and B to 0, the linear scaling settings do not affect computation, and the previous equation
becomes:
Auxiliary input measured value = SX – NULL
You can scale the auxiliary input by setting the scaling factor to the number of units per 1 V.
When There Is Offset in the Auxiliary Input Voltage
If you set S to 1, the scaling factor does not affect the computation, and the previous equation becomes:
Auxiliary input measured value = AX + B – NULL
You can scale the auxiliary input by setting the offset value (B) and setting the auxiliary input slope (A) to the
number of units per 1 V.
If you enable the NULL function and then change the auxiliary input slope (A) or offset value (B), NULL
correction will be offset. Reset the NULL value.
Computing the Auxiliary Input Slope and Offset by Specifying Two Points (Calculation)
On the input characteristic graph of the external input signal, you can specify two measured unit values (Point1Y
and Point2Y) in relation to two input voltage values (Point1X and Point2X). Select Execute to use these four
values to determine and set the auxiliary input slope (A) and offset (B).
Measured values (Point1X and Point2X): –1.000 T to 1.000 T
Computed values (Point1Y and Point2Y): –1.000 T to 1.000 T
Select Execute to use these four values to determine and set the auxiliary input slope (A) and offset (B).
Measurement range
Point1
Point2
Point1X
Point2X
Point1Y
Point2Y
y=Ax+B
Input value
Measured value
5 Auxiliary Input Conditions (Option)