80224_MHW_650 L - 1250 L_07-2018_ENG - 73
5.2. 4-point input correction
The 4-point input correction lets you correct the reading of
the main input and/or of the remote setpoint input by setting
four values: A1, B1, A2 and B2.
To enable the function, set parameter Lin to 4.POIN (I.MAIN
menu).
The limitations are:
•
B1 must always be larger than A1;
•
B1-A1 must be 25% larger than the full scale of the
selected sensor.
The setting is limited to the preset scale LO.SCL... HI.SCL
on the I.MAIN menu. The offset function (parameter OF.
SCL, I.MAIN menu) remains active.
By using this function for linear scales (60 mV, 1 V, 5 V, 10 V,
20 mA) you can invert the scale.
The four values are set on the LINRZ menu as follows:
•
A1 = STP.00
•
B1 = STP.01
•
A2 = STP.02
•
B2 = STP.03
Example
Select Pt100 input with Lin = 4.POIN to obtain an RTD sen-
sor with 4-point input correction.
Input Pt100 with:
•
Lin = 4.POIN (Pt100 natural scale -200...850),
•
DEC.P = 0
•
LO.SCL = 0
•
HI.SCL = 400
The reference points on the real curve (input) are:
•
A1 = STP.00 = 50,
•
B1 = STP.01 = 350,
B1-A1 = 300, which is larger by 212,5 (25% of 850).
The corresponding points on the corrected curve (indica-
tion) are:
•
A2 = STP.02 = 120,
•
B2 = STP.03 = 220.
With the corrected curve an input value of 200 is displayed
as 170.
Figure 14 - Diagram of 4-point input correction, for the
example (Pt100 input)
Indication
Without
correction
With
correction
Input
A1 = 50
A2 = 120
B2 = 220
B1 = 350
0
0
400
400
200
170
5. EXAMPLES AND APPLICATION NOTES