SI-3404 Ultrasonic Gas Flow Meter
Ultrasonic gas flow meter is based on the transit-time measurement principle. It features built-in digital temperature and pressure transmitters, integrated wireless communication module, and combines flow measurement, volume correction, and remote data transmission in one velocity-type gas metering instrument. Key advantages include high measurement accuracy, excellent reliability, low pressure loss, and wide turndown ratio. It meets the high-precision metering requirements of the city gas industry and is widely used in city gas, chemical, power, metallurgy, and trade custody transfer applications.

| Medium | GAS, Natural Gas LPG gas, natural gas, Oxygen, nitrogen, air etc. |
| Diameter | DN25-DN300 |
| Accuracy | 1.4% , Repeatability: 0.4% 1.0% , Repeatability: 0.2% |
| Output | Pulse / RS485 |
| Pressure | 1.6Mpa, 2.5MPa, 4.0MPa, 16MPa, 40MPa |
| Protection | IP 65 |
Features
Ultrasonic gas flowmeter has no moving parts and includes self-diagnostic functions, helping reduce maintenance workload, lower supply-demand discrepancies, and improve lean management. The accompanying PC software enables comprehensive data collection, diagnostics, and parameter configuration with role-based access control.

Specifications
| Parameter | Specification |
| Measuring Principle | Ultrasonic transit-time |
| Acoustic Paths | Dual-path (DN25/32/40/50/80/100), Triple-path (DN150/200) |
| Accuracy | 1%, Qt = 10Qmin |
| Medium Temperature | -25°C to +60°C |
| Ambient Temperature | -30°C to +60°C |
| Pressure Rating | PN16 |
| Explosion Protection | Flameproof: Ex d IIB T6 Gb; Intrinsically safe: Ex ib IIB T4 Gb |
| Ingress Protection | IP65 |
| Measured Values | Working flow, working accumulated volume, standard flow, standard accumulated volume, temperature, pressure |
| Measured Media | Natural gas, air, nitrogen, and other non-corrosive gases |
| Output Signals | Standard pulse: 0–3.2 kHz (OC output, N.O., ext. power required); Low-frequency pulse: 0.1/1/10 m³/p selectable (OC, N.O., N.C.); Analog: 1-ch 4–20 mA two-wire (optional); Low battery/under-pressure alarm: OC output, N.O., N.C. |
| Communication | RS485, Bluetooth, Wireless (GPRS, NB-IoT, or 4G) |
| Display | LCD |
| Installation | Flange connection (GB/T 9113 standard) |
| Body Material | Cast aluminum |
| Power Supply | External: +10V to +24 VDC; or Internal: +7.2 VDC lithium battery (metering battery + communication battery) |
Flow Range
| Model | DN (mm) | Flow Range (m³/h) | Transition Flow Qt (m³/h) | Start-up Flow (m³/h) | Turndown Ratio | Max Pressure (MPa) | Accuracy |
| DN25 | 25 | ~40 | 5 | 0.1 | 0.097222222 | ≤1.6 | 1% (Qt=10Qmin) |
| DN32 | 32 | 0.5–65 | 5 | 0.1 | 0.131944444 | ≤1.6 | 1% |
| DN40 | 40 | 1.0–100 | 10 | 0.2 | 0.111111111 | ≤1.6 | 1% |
| DN50 | 50 | 1.0–160 | 10 | 0.2 | 0.152777778 | ≤1.6 | 1% |
| DN80 | 80 | 2.5–400 | 25 | 0.5 | 0.152777778 | ≤1.6 | 1% |
| DN100 | 100 | 4.0–650 | 40 | 0.8 | 0.152777778 | ≤1.6 | 1% |
| DN150 | 150 | 16–1600 | 160 | 3.2 | 0.111111111 | ≤1.6 | 1% |
| DN200 | 200 | 25–2500 | 250 | 5 | 0.111111111 | ≤1.6 | 1% |
Built-in Pressure Transmitter Specifications
| Parameter | Specification |
| Type | Digital, absolute pressure |
| Range | 0–0.5 MPa (SZ-P-05) / 0–1.0 MPa (SZ-P-10) / 0–1.6 MPa (SZ-P-16) |
| Accuracy | ≤ ±2.5‰ FS |
Built-in Temperature Transmitter Specifications
| Parameter | Specification |
| Sensor Type | PT100 |
| Range | -25°C to +60°C |
| Accuracy | ≤ ±0.5°C |
RS485 Communication Parameters
| Parameter | Specification |
| Protocol | Standard MODBUS/RTU |
| Baud Rate | 1200 bps – 115200 bps (configurable) |
| Slave Address | 0–255 |
Mobile APP Functions
- Bluetooth connection — Connect to the flowmeter via smartphone app over Bluetooth
- Data query — Read historical data and event logs
- Parameter configuration — Remote meter reading and parameter settings
Online Monitoring System
- Wireless network monitoring — Data transmitted via wireless network (GPRS/NB/4G) to online monitoring platform
- Fault alarm — System monitors flowmeter status with fault alerts and trend prediction
- Remote meter reading — Full remote meter reading capability
Order Guide
In addition to regular products, we support customization
Model code: SI-3121 – ☐ – ☐ – ☐ – ☐ – ☐ – ☐ – ☐
| Position | Code | Description |
|---|---|---|
| Pipe Size | 025 | DN25 |
| 032 | DN32 | |
| 040 | DN40 | |
| 050 | DN50 | |
| 080 | DN80 | |
| 100 | DN100 | |
| 150 | DN150 | |
| 200 | DN200 | |
| Explosion Protection | i | Intrinsically safe |
| d | Flameproof | |
| Working Pressure | 00 | No pressure transmitter |
| 05 | 0.5 MPa | |
| 10 | 1.0 MPa | |
| 16 | 1.6 MPa | |
| Medium | A | Air, nitrogen, etc. |
| G | Natural gas | |
| Wireless | G | GPRS |
| N | NB-IoT | |
| H | 4G | |
| Z | None | |
| Optional | I | Analog output (4-20mA) |
| Z | None | |
| Measurement Direction | U | Unidirectional |
| B | Bidirectional |
Order example: SI-3121-i-080-10-G-G(E)-Z-U = Intrinsically safe, DN80, 1.0 MPa, natural gas, GPRS (external antenna), no analog output, unidirectional.
Notes: Antenna is built-in by default; add “(E)” after wireless code for external antenna. For units without pressure transmitter, the pressure value is user-specified at factory.

Applications
Intelligent gas ultrasonic flow meter can be widely used in:
petroleum, chemical industry, electric power, metallurgy, urban gas supply and other industries to measure the flow of various gases, is currently the oilfield and urban natural gas transmission,and distribution measurement and trade measurement of the preferred product.
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Our ultrasonic gas flow meters are manufactured using advanced German technology, with key components sourced directly from the manufacturer. They feature high reliability, stable performance, and long service life. This high-precision, high-reliability instrument can be widely used for gas flow measurement in industries such as urban gas, petroleum, chemical, power, and metallurgy.
Sino-Inst’s ultrasonic gas flow meters employ a multi-channel design, eliminating the effects of eddies and asymmetrical flow. The multi-channel design adds redundancy and backup channels, improving system reliability. Please feel free to contact us for consultation.
Zhang Wei, possesses 20 years of experience as an automation instrumentation engineer, specializing in the research, design, installation, commissioning, and maintenance of automation instruments.
Face to various instrument communication protocols (such as Modbus, Profibus, etc.), with solid hardware circuit design and software programming skills (proficient in C language and PLC programming). Has extensive project experience; projects he has led and participated in have all achieved outstanding results, improving product accuracy, reducing costs, and increasing production efficiency.
Possesses excellent communication and coordination skills and a strong team spirit, enabling him to quickly respond to customer needs and provide high-quality automation instrumentation solutions.