Sutron Corporation X-Link Operations & Maintenance Manual, Rev 1.63 5/24/2016 pg. 85
NOTE: X-Link does not provide a dedicated power supply for 4-20ma sensors.
The sensor shall have its own supply or run off the 12 volt supply of X-Link.
While the internal 4-20 measurement is made using an accurate 100 ohm resistor,
the overall loop resistance is 200 ohms due to an additional 100 Ohms series
protection resistor. This means that a sensor at a full 20 ma current output,
approximately 4 volts should be allotted for overhead voltage. This is typically
not an issue when an external voltage source is provided to operate the sensor that
may be in the 18 to 24 volt range. However, if a 12.5 volt battery is used to
source the voltage for the sensor in the current loop, then only 8.5 volts will be
supplied to the sensor at max sensor current output. Therefore if a full 12 volts is
necessary for the sensor, an external loop supply will be necessary or alternately
the sensor may be wired to a single ended voltage input with the use of an
external 100 Ohm accurate and stable resistor also attached to the voltage input
port.
7.1.4.15.
Warmup
Analog sensors are powered by X-Link via one of several outputs:
VREF (reference voltage) which provides 2.5V, terminal #19
Switched Power which provides whatever voltage is powering X-Link,
presumably 12V, terminal #10
Normally, these outputs are off. Prior to making an analog measurement, X-Link
will turn on these outputs. After that, X-Link waits
Warmup
amount of time
(which is expressed in seconds) before measuring the output of the sensors. This
Warmup
time gives the sensors a chance to power up and prepare their outputs.
If
Warmup
is set to zero, X-Link will not wait at all prior to measuring. The value
Warmup
should be set to depends on the analog sensor being measured.
Warmup is also used for
Digital and SDI-12
type sensors. If a such a sensor (or
a wind sensor that uses digital or SDI-12 inputs) is set up with a warmup, then
VREF and Switched Power will both be turned on. If warmup is set to zero,
those output lines will not be turned on. This is different for
Analog
measurements which turn on the lines regardless whether warmup is zero.
7.1.4.16.
Battery
This type measures the voltage of the battery connection to X-Link. This
measurement is a useful diagnostic for tracking the performance of the battery
and any solar panel or other charging equipment.
7.1.4.17.
Wind
X-Link supports a variety of wind sensors, including RM Young and Gill Ultrasonic
sensors. Any sensor that provides an analog, frequency, or SDI-12 output can be
handled by X-Link. RS-232 sensors are
not
supported.
