Compensation; Default Setting Of The Registers - Beckhoff KL3224 Documentation

Access from the user program
5.3.2

Compensation

Implemented linear 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
5.3.3

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.
28 Version: 2.0.0 KL3224