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Siemens
TX-I/O™ Module system – Functions and operation
CM110561en_08
Building Technologies
Analog input functions
2018-10-25
The functions require one I/O point.
10
56
1Z
10
6
I/O status LED
Field device
Signal Processing
LCD
Process value
BUS
Compensation
Block diagram of function
•
The function measures the input signal at regular intervals
•
The process value is calculated according to the signal
•
The admissible range for the input values is monitored so that any signal out of
range / sensor short circuit / sensor open circuit is identified. Exception: an open
circuit of a single conductor cannot be detected for the signal types AI Pt100 and
AI Pt100 4 wire.
The range monitoring of signal type U10 is done with a short NEGATIVE signal of –
3,1 V, 0.05 mA (open circuit detection). If a field device has an open output, a
negative voltage could appear there. This can damage any polarized components
(e.g. capacitors).
•
For temperature measuring, the process value is corrected by the internal
Compensation
value (0.00…100.00 Ohm, default = 1 Ohm), to compensate for the
line resistance. Pt100_4, P100, NTC10K and NTC100K: 0 Ohm.
•
If the line resistance differs significantly from 1 Ohm, [Icpt] can be changed in the AI
block (see description in [6]).
•
COV Limit
and
COV Period
define the amount of change and the interval for updates
to be sent on the island bus by the module.
•
As a result
– the
I/O status LED,
which describes the
source signal
, is activated
– the
process value
is displayed on the
LCD panel
(not for temperatures)
– the
process value
is communicated over the bus.
Analog inputs cannot be overridden locally. The override button has no effect, and if an
attempt is made to operate it, an error is displayed.
•
The
I/O status LED
varies in intensity in proportion to the
input value
(voltage,
current, resistance). There is no display for temperature (
P-Bus BIM
also resistance)
•
If an
LCD panel
is available, the input signal is displayed, together with a graphics-
based display of the
process value
(voltage and current, resistance).
There is no variable display for temperature (
P-Bus BIM
also resistance).
•
Field device faults
(invalid process value, values below low limit or above high limit,
short circuit and open circuit) are displayed on the LCD and reported to the bus
master.
•
The I/O status LED and the module status LED flash
For details, especially in relation to flashing pattern and errors: refer to the section "Dis-
play, operation and diagnostics" in the TX-I/O™ Engineering and installation guide [6].
Hardware
Function
STOP
Note!
Local override
Display
Temperature Voltage, current, resistance
1056
1D
306
V A
Ni
Ω
Pt T1
Response in the
event of a fault