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Key Features

• Time-difference correlation principle for flow calculation

• Accuracy classes: 0.5 and 1.0

• Fits pipe sizes from DN25 to DN300

• Supports single, dual, four, and six-channel configurations with channel fusion algorithm

• Low-noise signal processing with automatic temperature drift and zero drift compensation

• High-precision temperature/pressure acquisition and standard volume correction

• Turndown ratio > 1:160 with分段 meter factor settings

• Large on-board data storage:

  • 5,000+ historical records

  • 1,000 start/stop records

  • 100 alarm records

  • 20 months of cumulative totals

• Gas composition and compressibility factor calculation (AGA8-92DC or SGERG-88)

• Meets GB/T 18604-2014 and JJG 1030-2007 standards

• Intelligent transducer fault detection

• Supports lithium battery or external DC power

Working Principle

The module uses the transit-time difference method. Ultrasonic waves travel faster downstream and slower upstream. The flow velocity $V$ is calculated from the upstream and downstream transit times:

V=L2cos⁡θ(1tdown−1tup)V=2cosθL​(tdown​1​−tup​1​)

where $L$ is the path length, $\theta$ is the installation angle, and tdowntdown​, tuptup​ are the transit times. Volumetric flow rate $q=V\times S$ (S = pipe cross-sectional area). A cross-correlation algorithm transforms signals to the frequency domain, ensuring high noise immunity and stability.

Standard Volume Correction

The flow rate under working conditions is converted to standard conditions (101.328 kPa absolute, 0°C or 20°C) using the real gas equation:

qn=qf×pfpn×TnTf×ZnZfqn​=qf​×pn​pf​​×Tf​Tn​​×Zf​Zn​​

Where qnqn​ = standard volumetric flow, qfqf​ = working volumetric flow, $p$ = absolute pressure, $T$ = thermodynamic temperature, $Z$ = compressibility factor (AGA8-92DC or SGERG-88).

Technical Specifications

Standards

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

Accuracy

• Velocity range: 0.05 m/s to 30 m/s

• Class 0.5:

  • Qt~Qmax: ±0.5% (repeatability ±0.1%)

  • Qmin~Qt: ±1.0% (repeatability ±0.2%)

• Class 1.0:

  • Qt~Qmax: ±1.0% (repeatability ±0.2%)

  • Qmin~Qt: ±2.0% (repeatability ±0.4%)

  • Qt = 0.1 × Qmax

Power Supply

• Internal battery: 3.6 V lithium, average power < 5 mW, battery level display with two low-voltage alarms

• External DC: 12–24 V, ripple ≤50 mV, automatic switch-over, backlight on, average power < 1 W, electrical isolation

Compatible Sensors

• Dedicated ultrasonic transducers (supplied with module)

• I²C digital temperature sensor (specified model)

• I²C absolute pressure sensor (specified model)

Output Signals

Data Storage

• Last 5,000 records: timestamp, temperature, pressure, working/standard flow & accumulations (logging interval 1–60 min)

• Last 1,000 start/stop events

• Last 100 alarms (flow over limit, sensor fault, etc.)

• Last 20 months of working and standard accumulations

Environmental & Operating Conditions

• Ambient temperature: –20°C to +60°C

• Relative humidity: 5% to 95%

• Atmospheric pressure: 50–110 kPa

• Medium temperature: –20°C to +60°C

• Medium must be free of oil and impurities; flow and pressure within specified range.

Display & Operation

• Totalizer range: 0–9,999,999,999 Nm³ (standard) or m³ (working)

• Flow rate display: 0–±999,999 Nm³/h or m³/h

• Temperature: –99.9 to 99.99 °C

• Pressure: 0–9,999 kPa

• Battery icon: 0–3 bars

• External power icon & backlight

• Flow direction indicator (forward/reverse)

• Sensor fault indication (-ER- flashing)

Keys:

• BP1: Next page / save

• BP2: Cursor shift (digit selection)

• BP3: Increment digit

• BP4: Confirm / exit

Modbus RTU Communication

• Protocol: Modbus RTU, master-slave query mode

• Parameters: 1 start bit, 8 data bits, 1 stop bit, no parity (configurable). Baud rates: 2400, 4800, 9600, 19200 (default 19200)

• Slave address: 1–247 (default 1)

• Function code: 0x04 (read input registers)

• Data format: Big-endian, floating-point (single precision) or 64-bit unsigned integer (accumulations scaled by 1000)

• Register examples:

  • 0x0000: working flow (m³/h)

  • 0x0002: standard flow (Nm³/h)

  • 0x0004: working accumulation (positive)

  • 0x000C: temperature (°C)

  • 0x000E: pressure (kPa)

  • 0x0010: battery (%)

Diagnostic registers for each channel provide transit times, time difference, sound velocity, gas velocity, gain, and SNR.