Siemens S5-135U/155U appendix Differential, Measurement, Jumper between M+ and M

Analog Input/Output Modules

The following figure shows the connection of sensors to the module. For measurement with respect to ground, all the M- connection points are interconnected internally on the module.

			Analog Input Module
			M+
U E2	+		M+
	±		MUX
	U E1	+	M±
		±
			U ISO
			0 V Bus

U E1/2: Input Voltage

U ISO: Potential Difference

: Equipotential; this potential is established by the sensor reference potential (external reference potential)

Figure 9-30 Connecting Sensors to the 466 Analog Input Module (Measurement with Respect to Ground)

Differential	The differential measurement is a method of compensating for interference
Measurement	on the line. Each signal source is assigned its own signal reference line. The
	differential measurement between signal line and signal reference line thus
	compensates for the interference acting on both lines.
	You must also short-circuit the unused channels with this measuring method
	(jumper between M+ and M-).

Differential measurement is required:

Sif the sensors are at different potentials;

Sif various signal sources are not close to each other;

Sif there is a need to measure signals with high precision;

Sand when a high level of interference is expected.

System Manual	9-89
C79000-G8576-C199-06