BECKHOFF KL3201 - Manual (Page 18)

Register Description
16 KL3201, KL3202 and KL3204
Status byte for process
data exchange The status byte is transmitted from the terminal to the controller. The status
byte contains various status bits for the analog input channel:
status byte:
Bit 7 = 0
bin
Bit 6 = 1
bin
: ERROR (general error bit)
Bit 5 to bit 2: reserved
Bit 1 = 1
bin
: Over range
Bit 0 = 1
bin
: Under range
Compensation Implemented straight-line equation
Y[Ω] = (X_Adc * G + B_h) * A_h + 100 Ω
Hence:
B_h consists of a component that depends on the gain of the A/D converter
and a constant for calculating the axis offset of 100 Ω. The gain-dependent
component calculates the offset of the external components (the offset of
the component can be varied via adjustable amplification). This procedure
is necessary, because compensation at 0 Ω is technically not possible. The
line is therefore compensated around the point 100 Ω (offset to the point
and rotated around this point).
B_h: (B_off * G + B_100)
• Offset compensation should therefore be carried out for PT100 at
100 Ω (or PT1000 at 1000 Ω).
• Gain compensation is then carried out independently of the offset,
e.g. at 300 Ω. 300 Ω corresponds to 557.7°C = 0x15C9
Default setting of the
registers: R17: 0xED68 corresponds to -90.8 Ω
R18: 0x4E20 corresponds to 2000 * 16
-5 = 0.01907 Ω/digit
R19: 0x0000
R20: 0x00A0
R32: 0x0106
R33: 0x0000
R34: 0x0100
The gain and offset compensation only has to be carried out once, i.e. it
does not have to be repeated or corrected for any of the other implemented
elements.
For the two-wire connection, with short-circuited line resistance (+R1-Rl1)
the raw ADC value of the line resistance (contained in R1) has to be
entered in register R21.