XLINK 500/100 Operations & Maintenance Manual page # 84
Inputs 0-5V A and 0-5B are designed to be general purpose 0-5 Volt DC input. While sometimes
referred to as a single-ended input, it is designed to measure voltage with respect to analog
signal ground. These inputs have a high impedance (>2 Meg Ohms) and will not load down or
draw significant current. The input range is 0V to 5V. Negative voltages with respect to SIGNAL
GROUND may NOT be measured on these inputs.
To connect a sensor:
The voltage
output
by the sensor should be connected to either A or B.
The
analog ground
from the sensor needs to be connected to Signal ground.
The sensor will likely require
power
–
connect that to VREF if 2.5V is appropriate or to
+SWD#1 POWER which is 12V (or whatever power the station is supplied with). Make sure to
set up the warmup (the amount of time to power the sensor before reading its output) as
required by the sensor.
If the sensor has a power ground, connect that to Signal Ground.
Diff C, Diff D
Connection: Diff C (Terminals #28 and #27)
Connection: Diff D (Terminals #24 and #23)
Optional connection to VREF (#25 or #21) and Signal ground (#26 and #22) as
needed
Measurements Diff C, and Diff D are designed to operate with a special type of analog output
found on many sensors that use a bridge configuration or any sensor that outputs a very small
voltage. This input type has a + and - input that connects to the sensor output.
Typically, a bridge sensor will be powered on VREF (sometimes referred to as excitation), have a
and signal
–
, and provide a wire for the analog ground. NOTE: If after wiring the sensor, it
displays a negative reading, you may reverse the + and - leads coming from the sensor.
Reading Negative Output Voltages on Differential Inputs:
In limited cases, sensors with negative outputs may be used on the differential inputs with the
following limitations:
The negative line from the sensor must not connect to the digital ground of the sensor
with the sensor making a ground connection to the ground (including antenna ground)
of the station. (i.e. the sensor outputs must be able to be floated with respect the
grounding of the sensor itself)
The negative voltage (or positive voltage) must remain within the range of the
differential input range selected.
The common mode input range of the differential inputs must not be exceeded (see
below).
While the differential inputs are capable of reading negative voltages, it is important to keep the
voltages with respect to ground within in the common mode input range of 0.5 to 3.7 volts. In
the case of a bridge sensor, by using the Vref and signal ground to establish the voltage on the
network, you are assured of having a positive voltage with respect to signal ground. In the case
of the bridge, you simply need to remain within the voltage range selected (see 6.1.4.12 below)
and simultaneously remaining in the common mode range of the inputs or 0.5 volts to 3.7 volts.
