Special Features Of The 465 Analog Input Module - Siemens S5-155U System Manual

9.5.3
Special Features of the 465
Analog Input Module
Broken wire signal
Switching the tripping current
to the inactive state
Measuring range exceeded
Cyclic sampling/selective
sampling
System Manual
C79000-B8576-C109-03
The 465 analog input module executes integrating processing of the
digital input signals; periodic system interference is thus suppressed.
You can adapt the process signals, according to the application, to the
input level of the analog-to-digital converter of the module with
plug-in range cards (resistor dividers or shunt resistors).
To monitor the sensors connected to the inputs, you can use the
6ES5 498-1AA11 range card (through-connection card) to implement
the "broken wire detection" mode. You can activate broken wire
detection for 8 or 16 inputs in 16-channel operation, and for 4 or 8
inputs in 8-channel operation.
Each time the input value is about to be encoded, a constant current is
briefly (1.6 ms) switched to the input terminals and the resultant
current is checked for a limit value. If a digital voltmeter is used to
measure the signal at the input, these current pulses may appear to
indicate fluctuation of the signal. The encoded value, however, is not
affected.
If these apparent fluctuations of the signal are disturbing, e.g. during
startup, you can switch the tripping current to the inactive state on the
465 analog input modules: apply + 24 V to pin 24 of the front
connector, and 0 V to L-. You must additionally set the mode switch
to "without broken wire detection".
In the event of open-circuit of the sensor or its line, the voltage
exceeds the limit and a broken wire is indicated (bit 1 in data byte 1).
The analog-to-digital converter encodes the value 0.
A broken wire signal is only useful when the 6ES5 498-1AA11
through-connection card is used. With all other measurement cards, a
broken wire signal will result in incorrect reactions. Further details
relating to the broken wire signal can be found in Section 9.5.10.
If the measuring range is exceeded, the overflow bit (bit 2
byte) is set.
You have a choice of the cyclic sampling and selective sampling
modes.
In the cyclic sampling mode, the module continuously encodes all
measured values. The digitized measured values are stored under the
channel-related address on the module (the high byte under this
address, and the low byte under the next higher address). The
measured values can then be read by the module at any time without
waiting. When you operate the module in this mode, you can set a
module address from 0 to 255.
The 465 Analog Input Module
0
of the low
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