Product Details

Principle of Industrial Ultrasonic Flow Meter System:

Ultrasonic flowmeter is a volumetric flowmeter used to measure the flow rate of liquids, gases, or vapors. They are commonly used in the oil and gas, pharmaceutical, food and beverage industries. Flow meters use time-of-flight or Doppler technology to measure flow.

Flow meters that use the principle of time-of-flight have one or more pairs of sensors. By measuring the emission time of ultrasound in two directions, the flow rate can be calculated. This technology typically requires a relatively pure medium with a particle size of less than 5%. It can achieve an accuracy better than 1%.

When using the Doppler method, ultrasound pressure waves are reflected by moving particles in the fluid. The velocity of these particles produces a Doppler shift in the echo signal, which determines the flow rate. In practical applications, the accuracy of this measurement method usually does not exceed 3%.

Ultrasonic flowmeter includes power supply, sensor excitation, signal conditioning, analog-to-digital converter, processor, display screen, keyboard, and multiple communication options (such as 4 mA to 20 mA, HART, RS-485, wireless, etc.).

Design considerations and main challenges for industrial ultrasonic flowmeter systems:

This solution guide focuses on ultrasonic flow meters based on the principle of time-of-flight. The following signal chain is most suitable for applications that require high performance, especially those with multiple pairs of sensors. In addition to achieving high measurement accuracy, these designs often have quite strict spatial limitations.

The liquid ultrasonic flowmeter commonly uses a 1 MHz ultrasonic frequency. The system accuracy is directly related to the accuracy of upstream and downstream flight time measurements. Therefore, FPGA is generally used to control the timing of transmitting and receiving pulses. In addition, any possible deviation in the transmission and reception signal path delay must be taken seriously.

Another important aspect is that the receiving signal chain requires high gain. This gain needs to be dynamically adjustable to adapt to different flow conditions and pipeline sizes, with a typical range of 60 dB or higher, thus requiring a low-noise receiving signal chain path.

Sensor excitation can be on/off or waveform generator. Waveform generators typically increase cost and complexity, but users can better control the output signal, achieving more accurate and robust flow meter designs.

Signal processing requires extensive filtering and FFT analysis to determine the accurate timestamp of the received signal, which can be accomplished using a DSP processor that also supports the required interface protocols.