Thermocouple Input To Digital Conversion; Scaling Enabled; Scaling Disabled; Figure 9 2500C-8-Tc Example Of Change In Input Level - Control Technology 2500 Series Installation And Operation Manual

1.9 Thermocouple Input to Digital Conversion

1.9.1 Scaling Enabled

When module SCALING is enabled, data is reported as engineering units to the PLC as
follows:
Thermocouple Mode, digital word (WX) = Degrees x 10
Millivolt Mode, digital word (WX) = -10,000 to +10,000
As an example, the following Figure 1.3 illustrates the effects of a change in input level
going from 0 to 102.4
Example 1:
Example 2:

Figure 9 2500C-8-TC Example of Change in Input Level

1.9.2 Scaling Disabled

When data format is selected as SCALING disabled the full temperature range of the
thermocouple is reported as an unsigned integer from 0 to 32000 for thermocouple units or
–32,000 to +32,000 for mV units (range of +/-55mV). The following formulas may be used to
calculate the scaled integer value for temperature and mV.
Temperature: Scaled Integer = (measured temp - min temp) / (max temp - min temp) x
32000
example: the scaled integer offset at 0
Scaled integer = (0 - (-210)) / (760 - (-210)) x 32000 = 6928
example: the scaled integer overrange at 770
Scaled integer = (770 - (-210)) / (760 - (-210)) x 32000 = 32330
mV: Scaled Integer = mV x (32,000 ÷ 55)
example: the scaled integer offset at 20 mV is:
Scaled Integer = 20 x (32,000 ÷ 55) = ~11636.36
2500C-8-TC Installation and Operation Guide
o
F in the Thermocouple Input Mode.
o
0.0 F = (Digital Word (WX))/10
MSB
1 2 3 4 5 6
0 0 0 0 0 0
. . . . . .
o
102.4 F = (Digital Word (WX))/10
MSB
1 2 3 4 5 6
0 0 0 0 0 1
. . . . 1024
7 8 9 10 11 12 13 14 15 16
0 0 0 0 0 0
. . . . 32 16
7 8 9 10 11 12 13 14 15 16
0 0 0 0 0 0
. . . 32 16
o
C for a Type J thermocouple is:
o
LSB
0 0 0 0
8 4 2 1
LSB
0 0 0 0
8 4 2 1
C for a Type J thermocouple is:
11