BECKHOFF FM33xx User Manual

Page 36

FM33xx

R21: Cold junction compensation adjustment
Unit: 1/10 degree Celsius, 16-bit signed int

There are 8 cold junction compensations, and these are distributed as
follows. The cold junction compensation is purely an offset adjustment.

Comp[0] Channel0 R21
Comp[1] Channel4 R21
Comp[2] Channel8 R21
Comp[3] Channel12 R21
Comp[4] Channel16 R21
Comp[5] Channel20 R21
Comp[6] Channel24 R21
Comp[7] Channel28 R21

The cold junction compensation for a channel is calculated as follows:

Cold junction compensation =
(((~channel) & 0x7) * U_compensation [(channel>>3)<<1]+(channel &
0x7) *U_compensation[((channel>>3)<<1)+1])/7;

e.g., for channel 20:
4/7*U_compensation[5]+3/7*U_compensation[4]

R26: Number of hardware channels valid
12 with the number of channels 0 - 12

the hardware is different => the two outer boards are inserted
all values != 12 result in a standard version

R32: Feature register

R32.0 1 User scaling active
0 User scaling inactive

R32.1 1 Manufacturer scaling active
0 Manufacturer scaling inactive

R32.2 1 Cold junction compensation is active
0 Cold junction compensation is inactive

R32.7...R32.4 0x0000 Output in 2 microvolts / digit
R32.7...R32.4 0x0001 Type K active
R32.7...R32.4 0x0010 Type J active
R32.7...R32.4 0x1110 Output the unprocessed ADC value in the process
data. Default output in 2 microvolts / digit.

R33: User scaling offset

R34: User scaling gain
Fixed point number /256,
so that 1 corresponds to a value of 256.