Siemens SITRANS FC410, Руководство по эксплуатации, Страница: 28 / 160

Description
3.5 Theory of operation
FC410 with Modbus
26
Operating Instructions, 02/2016, A5E33120874-AC
When the media flows through the sensor, Coriolis force will act on the measuring tubes and
cause deflection which can be measured as a phase shift between Pickup 1 and Pickup 2.
The phase shift is proportional to the mass flowrate.
The frequency (or period) of the vibration is a direct function of the process media density.
The frequency and amplitude of the driver is regulated to ensure a stable output from the 2
pickups. The temperature of the sensor tubes is measured to provide accurate
compensation for changes in the material stiffness. As a result the process media
temperature is also accurately measured.
The flow proportional phase signal from the pickups, the temperature measurement and the
driver frequency enable calculation and reporting of mass, density, volume, and temperature.
Digital signal processing (DSP)
The analog to digital conversion takes place in an ultra low noise sigma delta converter with
high signal resolution. With fast digital signal processing massflow and density values are
calculated using a patented DFT technology (Discrete Fourier Transformation). The
combination of this patented DFT technology and the fast DSP enables short response time
(< 10 ms) to changes in the measured values.
The built-in noise filter is configurable and can be used for improving the performance of the
flowmeter, in case the installation and application conditions are not ideal. Typical process
noise such as gas bubbles (two-phase-flow) can be reduced through the filter functions.