In actual industrial production, pipeline electromagnetic flowmeter
is a kind of commonly used for the flow measurement instrument, fluid measuring electromagnetic flowmeter signal sampling process, there will be various factors that affect the measurement data, the jamming signal composition is complicated, some strength is very big, sometimes even more than traffic signal, how to eliminate these interference signals and improve the sex ratio, has been more difficult in the process of electromagnetic flowmeter installation and use of problem, is the key to the design of electromagnetic flowmeter and installation.
Pipeline of electrode electromagnetic flowmeter, as a kind of metal material, although in different medium have to match the measuring electrode, electrolyte fluid being measured in contact with the metal electrode electrochemical reaction happens (
Is the corrosion process, electrode material of measured medium for salt, acid, alkali liquid is common)
, will produce polarization voltage on the electrode.
Measuring electrode metal material in the electrochemical reaction and liquid medium at the same time, the surface will produce an oxide film to balance this electrochemical reaction.
But when containing solid particles or fibrous serous fluid flows through the electrode, and solid particles in the process of friction and the electrode electrochemical reaction will destroy the protective film on the electrode made of balance is broken, measuring the electrode surface to form a protective film, when the electrode repeating this process, will be produced in the pipeline of the electromagnetic flowmeter electrode polarization voltage, thus influence on the measured signal.
There is a kind of situation, when we are in very low electrical conductivity measurement fluid, also can appear dc polarization voltage swing.
We call this phenomenon low conductivity measurement & quot;
The flow noise & quot;
When the current body of low conductivity to a certain extent, such as alcohol, the medium flow such as pure water, like mobile charge in the capacitor, displacement current is not ignored.
Application of the following formula, can approximately describe flow noise size.
Fluid flow friction lining pipes electromagnetic flowmeter has gathered near the electrode surface charge with mobile, and the polarization noise induced the change on the electrode.
Obviously, if the medium high dielectric constant, the displacement current, electrode movement of charge near also increased, with medium dielectric constant E pipeline flow noise increases with increased electromagnetic flowmeter.
According to the excitation frequency of the electromagnetic flowmeter may be in 100 ~ 400 hz.
Dc potential interference is often random drift.
Dc interference potential of the two electrodes of asymmetric will dc common-mode voltage transform into a differential mode voltage dc.
Dc differential mode voltage range is too big, can make the amplifier resistance pipeline electromagnetic flowmeter, undermine its linearity.
In the converter measurement circuit, capacitance isolation and removal of sampling signal circuit makes the output voltage dc interference is very small.
Electromagnetic flowmeter in the pipeline, in actual applications also should take measures to prevent the pipe wall of the pipeline under test electromagnetic flowmeter big medium corrosion potential difference.
When this happens, we need to take measures in a timely manner, the metal pipe before and after the equipotential connection, dc interference to reduce the electric potential and ensure the stability of electromagnetic flowmeter measurement signal.
In this paper by embellish instrument technology co. , LTD. Arrange release.
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