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Appendix B
Appendix B Data Formats and I/O Ranges B
-3
B.1.2 Percent of FSR
This mode is used by setting bits 0 and 1 of the data format/checksum
/integration time parameter to 01. The format used in Percent of FSR
consists of a plus (+) or minus (-) sign followed by five decimal digits
including a decimal point. The maximum possible resolution is 0.01%
with the decimal point fixed.
Data are given as the ratio of the input signal to the full-scale range.
Example 1
The input value is +2.0 V. The input module is configured for a range
of ±5 V. The response to the Analog Data In command is as follows:
+040.00 (cr)
The full calibrated voltage range ranges from -100% to 100% as
voltage input ranges are always bipolar. A ±5 V input would range
from -5 V
(-100%) to 5 V (100%).
In this example the input is represented by +40% of the full-scale range
which equals to (+(40/100) x 5 V = +2.0 V) the actual input value.
Example 2
The input value is 652.5
o
C, and a type E thermocouple (0
o
C to 1000
o
C)
is configured in the analog input module. The response to the Analog
Data In command is:
+065.25 (cr)
The result shows that the value of the input (652.5
o
C) is 65.25% of the
full-scale range (1000
o
C).
Thermocouple input ranges are always assumed to be bipolar with zero
being the point of symmetry. This holds true regardless of the specified
range of operation. For example, when we use a type J thermocouple
(0
o
C to 760
o
C), 760
o
C corresponds to +100% and 0
o
C corresponds to
0%. Even if 0
o
C lies outside of the specified operation range for the
thermocouple, zero will remain as the point of symmetry. For instance,
a type B thermocouple is specified for operation from +500
o
C to
+1800
o
C. In this case +1800
o
C corresponds to + 100% and 500
o
C
corresponds to +27.77%.