4-20 mA
Connection:10-11 for loop powered sensors
11, 13 for external powered sensors
SDR with Analog Input
Option.
10 11
24 v I-In
4-20
ma
Sensor
Example loop powered sensor.
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. MONITOR 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. MONITOR provides a
24 Volt supply that is designed just for the 2 wire interface 4-20ma loop.
Warmup
Analog sensors are powered by MONITOR via one of several outputs:
•
VREF (reference voltage) which provides 2.5V
•
Switched Battery which provides whatever voltage is powering
MONITOR, presumably 12V
•
24V which is normally used for 4-20mA sensors
Normally, these outputs are off. Prior to making an analog measurement,
MONITOR will turn on these outputs. After that, MONITOR 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, MONITOR will not wait at all prior to measuring. The
value
Warmup
should be set to depends on the analog sensor being measured.
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