FIEDLER H1, Руководство пользователя

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Hydro Logger H1 User manual
32
electronics for ecology
FIEDLER
4.4.4. Analog current inputs AV1, AV2
Inputs AV1, AV2 and AV3 (terminals 4, 7 and 8) can be used to connect sensors
and transducers with current output signals of 0-20 mA, 4-20 mA, 0-1 mA, 0-5
mA or 1- 5 mA. The type of current signal is set in the instrument parameters.
The following figure shows 3 possible ways of connecting the sensors to the
analog AV inputs of the instrument:
•
The sensors connected in 3 wires are shown in the 1st box with the
SPA340 sensor.
•
The two-wire connection of the sensor powered by a passive current
loop is represented by the 2nd box with the WL61 radar level sensor.
•
Separately powered sensors with an active current loop are shown by
the FLOWMETER in Box 3.
Three different ways to connect current analog signals to H1 inputs
Sensors and probes with current output include mainly strain gauge level sen-
sors. However, many other measuring probes and sensors can be connected to
the Hydro Logger H1 and H2 via these inputs, ranging from pressure sensors to
ultrasonic or radar level gauges to inductive flow meters.
The voltage drop across the AV input measuring resistor can be up to 2 V at 20
mA current. When connecting sensors powered over a two-wire current loop
(radar sensor WL61 in the upper picture), it is necessary to increase the mi-
nimum supply voltage of the connected sensor declared by its manufacturer on
the +Unap power terminal by this drop. On the other hand, an unnecessarily
high +Unap supply voltage excessively depletes the capacity of the power supply
battery.
The analogue signals fed to the AV1 and AV2 inputs are measured by a precision
transducer with a digital filter that suppresses interference voltages induced in
the input cable and performs automatic self-calibration of the measuring ran-
ges.
Vo l t a g e d r o p
a c r o s s i n p u t s