Siemens S5-135U/155U appendix Special Features of the 460 Analog Input Module

Analog Input/Output Modules

9.3.3Special Features of the 460 Analog Input Module

	The 460 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).
Broken Wire	To monitor the sensors connected to the inputs, you can use the
Signal	6ES5 498-1AA11 range card (through-connection card) to implement the
	ªbroken wire detectionº mode. You can activate broken wire detection for 4
	or 8 inputs.
	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.
Switching the	If these apparent fluctuations of the signal are disturbing, e.g. during startup,
Tripping Current to	you can switch the tripping current to the inactive state on the 460 analog
the Inactive State	input module: apply + 24 V to pin 24 of the front connector, and 0 V to L-.
	You must additionally set the mode switch to ªwithout broken wire
	detection.º
	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 9.3.12.
Measuring Range	If the measuring range is exceeded, the overflow bit (bit 2<M>0 of the low
Exceeded	byte) is set.
Cyclic Sampling	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.

9-8	System Manual
	C79000-G8576-C199-06