Overview

The precision intelligent gas ultrasonic flowmeter is a non-contact flowmeter based on the cross-correlation principle of the propagation time difference method, which uses ultrasonic waves to detect gas flow rate information in pipelines. Due to its advantages of high measurement accuracy, strong anti-interference ability, small pressure loss and wide measurement range, it has gradually been widely used in the field of gas flow detection in recent years.

The precision intelligent ultrasonic flowmeter adopts single/multi-channel design and complies with international standard ISO 17089, national standard GB/T 18604-2014 and enterprise standards

Feature Highlights

1. Adopt the cross-correlation principle based on the propagation time difference method;

2. Support accuracy level: level 1.0;

3. Caliber: DN25-DN300;

4. Low-noise signal processing circuit and temperature drift/zero drift automatic compensation algorithm;

5. Standard volume calibration integrating high-precision temperature/pressure acquisition and compensation;

6. The range ratio exceeds 1:160;

7. Ultra-low "zero" starting flow rate;

8. The meter head can be rotated 350° for easy reading;

9. Large-capacity onboard data storage, which can be maintained for more than one month;

10. Gas component setting and compression factor calculation comply with AGA8-92DC or SGERG-88 calculation methods;

11. Comply with national standards GB/T 18604-2014 and JJG 1030-2007;

12. Intelligent identification and automatic detection of transducer faults;

13. Supports lithium battery power supply and external DC power supply (the battery is emergency power supply, external power supply is recommended for long-term use);

14. This product uses a cross-correlation algorithm for the measurement and calculation of transit time, transforming the ultrasonic signal from the time domain to the frequency domain for processing, so it is insensitive to the signal amplitude, has strong anti-interference ability, wide measurement range, good data stability, and has significant advantages over other measurement methods.

Working principle of gas ultrasonic flow meter

The gas ultrasonic flowmeter measurement control module adopts the cross-correlation flow calculation principle based on the propagation time difference method. As shown in Figure 1, when the propagation direction of ultrasonic waves is the same as the direction of fluid flow (downstream), the speed increases and the propagation time becomes shorter; when the propagation direction is opposite to the direction of fluid flow (countercurrent), the speed slows down and the propagation time becomes longer. Where θ is the installation angle between the transducer and the axis of the pipeline, L is the distance between the two transducers, D is the diameter of the pipeline, the gas flow velocity in the pipeline is V, and the propagation speed of ultrasonic waves in the fluid is C.

(1) When ultrasonic waves propagate downstream, that is, transducer 1 transmits and transducer 2 receives, then the speed of ultrasonic waves in the L direction is V₁₂for:

(2) When the ultrasonic wave propagates counter-currently, that is, transducer 2 transmits and transducer 1 receives, then the speed of the ultrasonic wave along the L direction is V₂₁for:

(3) According to equations (1) and (2), the downstream transit time t of ultrasonic waves propagating in the fluid can be obtained_downfor:

(4) Countercurrent transit time t_upfor:

 (5) The length of the vocal tract L and the angle θ between the axes are both known quantities, and the transit time t is obtained._up and t_downThe gas flow velocity V in the pipeline can be calculated as:

(6) Multiply the cross-sectional area S of the pipe to further obtain the gas volume flow rate q, that is

The measurement of transit time plays an important role in flow calculation and directly affects the accuracy of flow measurement. Commonly used transit time calculation methods include the threshold detection method and the cross-correlation method. Since the signal is difficult to maintain stability when ultrasonic waves propagate in gas, the signal amplitude fluctuates greatly due to the fluid state, and the signal-to-noise ratio is low. The received signal may not be detected at the threshold voltage, making it difficult to ensure the accuracy of the transit time calculation.

This product uses a cross-correlation algorithm for the measurement and calculation of transit time, and transforms the ultrasonic signal from the time domain to the frequency domain for processing, making it insensitive to signal amplitude, strong anti-interference ability, wide measurement range, good data stability, and has significant advantages over other measurement methods.

Technical indicators

5.1 Product standards

Gas ultrasonic flow meters comply with the following national standards and measurement verification regulations:

•GB/T 18604-2014

•GB/T 34041.1-2017

•GB/T 32201-2015

•GB/T 17747

•GB/T 3836.4-2021

•GB/T 30500-2014

•JJG 1030-2007

5.2 Measurement accuracy level

1. Measured gas flow velocity range: 0.05m/s~30m/s

2. Level 1.0 accuracy level:

Qt~Qmax maximum allowable error: ±1.0%, repeatability: ±0.2%

Qmin~Qt maximum allowable error: ±2.0%, repeatability: ±0.4%

Among them Qt=0.1Qmax

5.4 Explosion-proof level: Ex ib IIB T4 Gb

5.5 Protection level: IP68

5.8 Measurement environment

>Ambient temperature: -20℃~+60℃

>Relative humidity: 5%～95%

>Atmospheric pressure: 50kPa～~110kPa

>Measure medium temperature: -20℃~+60℃

>The measured medium should be free of impurities such as oil and dirt, and the flow rate and pressure range should be within the range specified by the flow meter.

Measuring range

6.1 Gas ultrasonic flow meter level 1.0 (please fill in the model and specifications according to the actual situation)