Analog Data Bits - Automation Direct DL405 User Manual

Temperature Sign The most significant bit is used to note
the sign of the temperature. If this bit is
Bit
on, then the temperature is negative. If
the bit is off, then the temperature is
positive.

Analog Data Bits

The first twelve bits represent the
temperature. If you have selected the
0–4095 scale (counts), the following
format is used.
Bit
0 (LSB)
1
2
3
4
5
Temperature Input Typically, the F4–08THM–n resolution enables you to detect a 1_F change in
Resolution temperature. The National Institute of Standards and Technology (NIST) publishes
conversion tables that show how each temperature corresponds to an equivalent
signal level.
Millivolt Input Since the module has 12-bit resolution,
Resolution the analog signal is converted into 4096
counts ranging from 0 – 4095 (2
example, with a –2 (100mV) module a
signal of 0 mV would be 0, and a signal of
100 mV would be 4095. This is
equivalent to a a binary value of 0000
0000 0000 to 1111 1111 1111, or 000 to
FFF hexadecimal. The diagram shows
how this relates to the example signal
range.
Each count can also be expressed in
terms of the signal level by using the
equation shown. The following table
shows the smallest signal levels that will
result in a change in the data value for
each signal range.
F4–08THM–n 8-Channel Thermocouple Input
Value Bit
1 6
2 7
4 8
8 9
16 10
32 11
Range Signal Span
(H – L)
0 to 25 mV 25 mV
0 to 50 mV 50 mV
0 to 100 mV 100 mV
MSB
1 1 1 1 1 1
5 4 3 2 1 0
– temperature sign
V40401
MSB
1 1 1 1 1 1
Value
5 4 3 2 1 0
64
128
256
– data bits
512
1024
2048
0–100 mV Scale
12
). For
100mV
0 mV
0
Resolution + H * L
H = high limit of the signal range
L = low limit of the signal range
Divide By Smallest Detectable
4095
4095
4095
8–11
V40401
LSB
9 8 7 6 5 4 3 2 1 0
LSB
9 8 7 6 5 4 3 2 1 0
4095
4095
Change
6.1 mV
12.2 mV
24.4 mV