Sutron Corporation X-Link Operations & Maintenance Manual, Rev 1.63 5/24/2016 pg. 84
The common mode voltage for differential sensors is 0.5V to 3.7V. If the sensor
is floating, it should be tied to VREF and not to AGND in order to maintain this
common mode voltage. Sensors that are not powered by X-Link are generally
floating (such as a pyranometer).
7.1.4.13.
Input Range
This setting is relevant only to analog differential measurements. Remember
that the system must read a voltage that falls into the common mode range
mentioned in the above note. Voltages that are negative with respect to the
AGND terminal may not be measured. The following options are available:
-39 to +39mV
-312 to +312mV
-2.5 to +2.5V
Choose the option that is close to and greater than the input range of the sensor
that is being connected.
For example, if a sensor provides a reading from 0 to 100mV, choose the 312mV
option. If you were to choose the 39mV option, when the sensor provided a
reading greater than 39mV, the unit would indicate a sensor failure.
7.1.4.14.
4-20 mA
Connection: 4-20ma IN (Terminal #15 and #16)
This input is designed to function with sensors that have a 4 to 20ma current
loop interface. This type of interface is superior to voltage outputs when the
cables to the sensors must travel a long distance or when the equipment is
located in electrically noisy environments. X-Link will measure the current
flowing when connected to the 4-20ma Input. Typical 4-20ma sensors will give a
4 to 20ma current for a 0 and 100% FS. Readings that are greater than 21mA will
be considered a fault. The current required for the sensor is provided by the 2
wire loop and does not typically require additional connections.
