Inputs And Outputs Configuration; General Purpose Inputs And Outputs; Current Output - BASI BFM921 User Manual

Electromagnetic Flowmeter BFM921

5 Inputs and outputs configuration

5.1 General purpose inputs and outputs

5.1.1

Current output

Current loop 4 to 20 mA can be set as passive type connecting to terminals PAS and RTN or as active type
by connecting to terminals ACT and RTN. In both cases outputs are galvanically separated from all other
electronic circuits of the flowmeter. Voltage drop on the passive current loop is 4 V. Active current loop can
work with maximum load of 800.
5.1.1.1 Mode
Current loop output can be programmed in one of the following modes:
a) Off
b) Positive Flow
c) Negative Flow
d) Absolute Flow
e) Bipolar Flow
f) Fixed
5.1.1.2 Fixed current
Item allows setting current amplitude in the current mode f)
(Fixed). The range is from 4 mA to 20 mA. Fixed current mode
is suitable for testing purposes.
5.1.1.3 Flowrate for 20mA (Qi 20mA)
Item allows setting the Qi constant. Qi represents a flowrate
for a current of 20 mA and can be set independently to the
nominal diameter of the sensor. The range of Qi value is
proportional to the flowrate range of range of the flowmeter
(DN diameter).
5.1.1.4 Current loop test
Item allows enable/disable the current loop test. The flowmeter
will detect a fault (Error 08 – Current open) if the test is
enabled and current loop is not connected.
5.1.1.5 Error current
Item allows setting current loop error current from 3 mA to
3.75 mA or from 21 mA to 24 mA. Current output is switched
to selected value in case of present error state in flow meter.
24
current output is adjusted to 4mA (error message 01 - "Current output" is
switched off)
current 4+16*Flowrate / Qi [mA] is generated for a positive flowrate
direction. For a negative flowrate direction 4mA is generated.
current 4-16*Flowrate / Qi [mA] is generated for a positive flowrate
direction. For a positive flowrate direction 4 mA is generated.
current 4+16*abs(Flowrate) / Qi [mA] is generated for both flowrate
directions.
current 12+8*Flowrate / Qi [mA] is generated for both flowrate
directions.
current output is adjusted to fixed value (4.000 ... 20.000 mA)
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