Gas flow meters needs signal transmission
With the progress of modern industry, field
gas flow measuring instruments with only local display can no longer meet the
development of various industries. With the development of PLC, DCS and other industry
systems, gas flowmeters have added the function of remote transmission signals,
generally with 4-20mA signal output to access the control system.
Flow meter with analog output
Analog output is normally a standard output from our digital flow meters to connect control instrumentation. The flow meter is intended for continuously measuring of flow rates of the passing fluids. For analog output, the flow is changed to current output, normally we set 4mA to zero flow, and 20mA to the max flow. However te 20mA corresponding flow value can be changed through the flow meter digital indicators.
Why choose 4-20mA analog output for gas flow meter
1. The flowmeter voltage signal is
unstable, it is easily disturbed during long-distance transmission, and however
the current signal is relatively stable. The current signal is selected during transmission;
while the voltage signal is selected for detailed control in DCS system.
2. The signal with a range of 0~20mA cannot
be distinguished from the fault signal. Less than 4 mA indicates that the line
is faulty, or there is a possibility of zero drift. The birth of the two-wire system
gas measuring instrument promoted the revision of the specification, and the new
specification of the current signal was set at 4-20 mA.
3. 4-20mA is set for the two-wire gas flow sensor.
The current of 0-4mA is for small flow measurement. If 0-20mA is selected, when
the gas flow signal is small, the gas flowmeter sensor will not be accurate.
In fact, regarding the 4-20 mA signal, the
DCS system usually counts more than 20.2 mA and less than 3.8 mA as a fault
In summary, the 4-20 mA current signals have
been used as a standard configuration in the instrument industry, facilitating
automated production in all industries. In the process of new construction or
replacement, it facilitates and simplifies the procedure to maximize benefits.
The gas flow meter provided by Silver Automation
Instrument has 4-20Ma output
For example, the gas flowmeter, the vortex
gas flowmeter, the turbine gas flowmeter, the rotor gas flowmeter, etc., all
have a 4-20ma output.