Xylem H-5223 - Manual (Page 17)

Figure 2.3 Bridge Sensor
2.2.3.1 Analog Input Channels
There are four analog input channels labeled Vin1 to Vin4. The input range is 0 to 5 volts DC
and the maximum input should not exceed 5.0 volts. Each input can be programmed with a slope
and an offset allowing the final value recorded for the input to be scaled to some units of measure
like temperature or wind direction. Programming the slope and offset will be discussed in detail
in chapter 3.
2.2.3.1.1 Differential Input Option
Channels 1 and 2 can be used together to form a single differential input channel. This option is
intended for bridge type of sensors like a strain gage. This type of sensor has two output signals
that are referenced to each other, not directly to ground. See figure 2.3.
2.2.3.2 Analog Grounds
There are two analog ground connection points. In order to preserve signal integrity, it is
important to use the analog grounds only for sensors connected to the analog section of the
H-5223. The current flowing through an analog sensor is relatively small and normally very
stable. This provides stable voltages produced by these sensors. If a digital sensor has its ground
connection tied into the analog ground, the currents from the digital sensor will flow through the
analog circuitry causing voltage level shifts and noise based on digital switching. There should
be sufficient digital ground connection points for the digital sensors.
H-5223
Hardware Options and Installation 2-3