A low flow meter is a flow instrument specified for liquid or gas rates small enough that general-purpose meters lose resolution. In practice that means working in grams per hour, millilitres per minute or standard cubic centimetres per minute, and paying more attention to sensing principle, wetted material, pressure rating and calibration than to line size.

Silver Automation Instruments, a flow and pressure instrument manufacturer based in Nanjing, China, builds three families that are used in this range: the SH-CMF-FE micro Coriolis mass flow meter (40 g/h to 1000 kg/hr, ±0.25% to ±0.5%), the SRK-DL low flow thermal mass flow meter (2 sccm to 30 SL/M), and the SH-CM Coriolis mass flow meter, whose published range starts around 10 kg/hr. They do not compete for the same duty. Understanding where each one belongs is the whole of low flow meter selection.

Why Low Flow Deserves Its Own Instrument Category

The difficulty of small-flow measurement is not the small number on the display. It is that every physical effect in the pipe stops being negligible. A meter sized for a main process line sees a very low velocity at micro flow, so the energy or signal it generates sits close to its own noise floor. The measurement starts to depend on things that are normally ignored: the fluid temperature, the presence of a single bubble, the dead volume inside the sensor body, or the pulse pattern of a dosing pump.

Three practical consequences follow.

• Sensor size must be matched to the flow, not the pipe. A large meter on a small flow reads poorly regardless of how good its electronics are.
• Response time becomes a selection criterion. Dead volume holds fluid and delays the reading, which matters in dosing and in test benches.
• Small leaks are the same order of magnitude as the measurement. In leak detection duty the meter may be asked to resolve a flow of a few standard cubic centimetres per minute, which is why micro thermal sensors are used for that task.

What Is a Low Flow Meter?

A low flow meter is a flow sensor and transmitter combination whose usable measuring span, internal volume and signal resolution are matched to small flow rates rather than to large pipelines. It reports mass flow or normal volumetric flow directly, or reports volumetric flow with the fluid properties needed to convert it. The defining feature is the matched span, not a specific number.

Buyers meet this product category under several names, and the names describe slightly different emphases rather than different physics:

Industry Background: Where Low Flow Accuracy Is Being Demanded

Flow measurement overall is a mature market, but the small-bore and low-flow end of it is growing faster than the average. Grand View Research valued the global flow meter market at USD 10.64 billion in 2024, and identifies the 2-inch and smaller pipe size segment as the fastest growing through 2030, driven by pharmaceuticals and food and beverage.

Two adjacent segments show the same direction. Market Research Future reports that thermal flow meters, which are the workhorse for low gas flow rates, reached USD 1.73 billion in 2024 and are projected to reach USD 2.9 billion by 2035. Fortune Business Insights places Coriolis flow meters — the technology used for high-precision low-flow liquid measurement — at a 26.77% share of the intelligent flow meter market in 2026. P&S Intelligence sizes the microfluidic devices market, which includes micro flow sensors, at USD 22.1 billion in 2024 with a 12.2% CAGR.

The applications behind those numbers are specific. Silver Automation Instruments lists fermentation equipment, semiconductor processing, pharmaceutical production, food, (petro)chemical processing and fuel cell technology as the environments where its micro Coriolis meter is used, and semiconductor, medical, analytical instruments, fuel cells and environmental monitoring for its micro thermal meters. Those are processes where the flow rate is small, the fluid is expensive, and the consequence of a wrong reading is a failed batch or a mis-billed test.

The Three Measurement Approaches Compared

Almost every low flow decision resolves to one of three architectures: a micro Coriolis meter, a thermal mass flow meter, or a Coriolis meter sized down to reach low flow at the bottom of a wider span. The difference is mechanical, not commercial.

Micro Coriolis mass flow meters

A Coriolis meter measures mass flow directly, from the phase shift of a vibrating tube, so it does not need a density or composition assumption to report kilograms per hour. A micro Coriolis meter shrinks the tube so that the same principle produces a usable signal at very small mass flows.

The SH-CMF-FE is Silver Automation Instruments' micro Coriolis mass flow meter. It is specified for 40 g/h to 1000 kg/hr with an accuracy of ±0.25% to ±0.5%, a pressure rating of 30 bar or 100 bar, and a 316L stainless steel wetted path. Outputs are 4-20mA, 0-5VDC and 1-5VDC, with RS485 or RS232 communication and 15V DC or 24V DC power. It is available as a meter or as a controller, and it handles fluids including pure water, silicone, aviation kerosene, diesel, supercritical CO2 and silane. The published applications are food, (petro)chemical and pharmaceutical processing, fermentation equipment, semiconductor processing and fuel cell technology.

The practical argument for this design is that it covers gas and liquid in one instrument, keeps direct mass measurement, and holds a high pressure rating. The practical limitation is that a micro Coriolis meter is a precision instrument, and its cost reflects that.

Thermal mass flow meters for low gas flows

A thermal mass flow meter derives mass flow from heat transfer into a flowing gas. Because the heat transfer depends on the gas, the meter is calibrated for a known composition — which is why gas identity, not just flow range, belongs in the specification.

The SRK-DL is a low flow thermal mass flow meter covering 2 sccm to 30 SL/M with an accuracy of ±1% F.S., stainless steel construction, outputs of 0-5V, 4-20mA or 1-5V, RS232/485 with MODBUS, and ±15V DC or 24V DC power. That 2 sccm lower limit is why these meters appear in leak detection and in analytical instruments, as well as in semiconductor, medical, fuel cell and environmental monitoring duty.

For larger gas lines the same principle is available in the SRK-100 thermal mass flow meter, which covers DN15 to DN2000 in inline or insertion form, handles gas temperatures from -20 to 300 °C, and measures air, compressed air, N2, natural gas, biogas, O2 and LPG with a 4-20mA output and RS485, MODBUS RTU or HART communication. It is the right instrument for plant gas accounting; the SRK-DL is the right instrument for the few-sccm end of the range.

Coriolis mass flow meters across the wider range

When the low flow duty sits inside a broader operating window, a full-range Coriolis meter is often chosen instead of a dedicated micro instrument. The SH-CM covers sizes from roughly 1 mm to 300 mm and flow from about 10 kg/hr to 1500 t/h, with fluid temperatures from -200 to 350 °C, IP65 protection, 316L stainless steel construction, and communication over 4-20mA, pulse, frequency, MODBUS RTU, HART, Profibus-DP or Profibus-PA. It is ATEX certified.

The selection rule is straightforward. If the process will only ever run at low flow, a micro instrument gives better resolution per unit of span. If the process ramps from low flow to several tonnes per hour, a wide-range Coriolis meter avoids installing two devices — provided the low-flow end still meets the accuracy the process needs.

Low Flow Meter Comparison: Published Specifications

The table below uses only published figures from the manufacturer's product data. Blank cells indicate that the value is not part of the published specification for that model and should be requested with the datasheet.

Certification and Compliance: What to Verify Before You Buy

For a low flow meter, compliance documentation is not paperwork — it determines whether the instrument can be installed at all. Three certificate families matter most in export projects.

• CE. Silver Automation Instruments holds CE certification number 1N220422.SAIUW36, issued by Ente Certificazione Macchine Srl against EN IEC 61326-1:2021, scope flow meter, issued 5 May 2022 and valid to 21 April 2027.
• ATEX. Certificate ICR/VC/HM251296, issued by ICR, covers Zone 2 equipment against IEC 60079-0:2018+A11:2024, EN 60079-1:2014+A11:2024 and EN IEC 60079-31:2024, valid from 9 December 2025 to 9 December 2030. A second ATEX certificate, ECM 22 ATEX-B 0S05 from Ente Certificazione Maccine srl, covers the SRK-100 and SH-CM and runs from 21 February 2022 to 20 February 2027. The ATEX scope covers the SH-CMF-FE, STLU-VFN, SRK-DL, SRK-100 and SH-CM models.
• ISO 9001:2015. Certificate 79625Q0002107R0S, issued by ZHONGHONG CERTIFICATION (JIANGSU) CO.,Ltd, valid from 10 July 2025 to 9 July 2028, covering the quality management system behind the product line.

When comparing suppliers, ask for the certificate number, the issuing body, the standard cited and the expiry date — a claim of "ATEX available" without those four items cannot be checked. Note also that ATEX Zone 2 coverage and Zone 0/1 coverage are different scopes; confirm the zone your installation actually requires.

Step-by-Step: Specifying a Low Flow Meter

1. Write down the real flow window. State the minimum, normal and maximum rate in mass units (g/h, kg/hr) or normal volumetric units (sccm, SL/M). A meter chosen on the maximum alone will be poor at the minimum.
2. Confirm the fluid state and composition. Gas identity drives thermal meter calibration. For liquids, note viscosity and whether the fluid is pure water, silicone, aviation kerosene, diesel or a supercritical fluid such as CO2.
3. Match the wetted material to the medium. 316L stainless steel is specified on the SH-CMF-FE and SH-CM for corrosive chemical duty; 304 stainless steel is specified on the SRK-100 thermal mass flow meter.
4. Check pressure and temperature at the sensor. The SH-CMF-FE is rated for 30 bar or 100 bar. The SH-CM accepts fluid temperatures from -200 to 350 °C, and the SRK-100 accepts gas from -20 to 300 °C.
5. Set the accuracy requirement against the process. ±0.25% to ±0.5% on the SH-CMF-FE and ±1% F.S. on the SRK-DL are two different classes of instrument; specifying the tighter one where it is not needed adds cost without adding value.
6. Verify hazardous area and market compliance. Confirm ATEX zone, the CE certificate scope and the ISO 9001 certificate validity before the purchase order, not after.
7. Match the signal to the control system. Decide between 4-20mA, 0-5VDC, 1-5VDC, pulse or frequency, and between RS232/RS485, MODBUS RTU, HART, Profibus-DP and Profibus-PA. Decide whether you need a meter or a meter with integrated control.
8. Validate on a sample or a calibrated unit. Request a unit at the real flow window and review the calibration record before committing a production line to the design.

Use Cases: Where Low Flow Meters Are Specified

Fuel cell test and fuel cell systems. The SH-CMF-FE lists fuel cell technology among its applications and handles gases including silane and supercritical CO2 alongside liquids such as pure water and diesel. Direct mass measurement matters here because the reactant flow is small and the test result is reported per unit of mass delivered.

Semiconductor gas delivery. The SRK-DL is specified for semiconductor processing and analytical instruments, with a 2 sccm lower limit. The same product family is used in medical and environmental monitoring equipment where the gas flow is small and continuous.

Fermentation and pharmaceutical production. Both the SH-CMF-FE and the SH-CM list fermentation equipment and pharmaceutical processing among their applications. Small liquid flows with direct mass output avoid the density assumptions that volumetric metering would require.

Chemical and fuel metering. Aviation kerosene, diesel and supercritical CO2 appear in the SH-CMF-FE fluid list, and the SH-CM is applied to fuel mass flow. Where the medium is aggressive, the 316L wetted path is the selection point.

Leak detection at 2 sccm. A customer in China used three SRK-DL micro thermal mass flow meters to detect air leakage down to 2 sccm, and reported sensitivity to leaks as low as 2 ml/min over more than ten years of service. This is the clearest illustration of why the low-flow end of the range is a separate product category.

High-pressure gas. A separate case used a Coriolis meter to measure nitrogen at approximately 700 bar, with stable measurement maintained for more than three years. High pressure is a mechanical requirement, not a flow requirement, and it must be specified separately from the flow range.

Frequently Asked Questions

Conclusion

Low flow metering is a specification problem before it is a product problem. The flow window decides the architecture: 2 sccm to 30 SL/M points to a micro thermal mass flow meter such as the SRK-DL; 40 g/h to 1000 kg/hr with direct mass output and a high pressure rating points to the SH-CMF-FE micro Coriolis meter; a process that also runs at tonnes per hour points to the SH-CM. Accuracy class, wetted material, pressure and temperature limits, and certification scope then narrow the choice to one model.

What separates a good outcome from a bad one is rarely the instrument. It is whether the flow window was measured rather than guessed, whether the certification was verified rather than assumed, and whether a unit was tested before the line was committed.

Market figures cited in this article are attributed to Grand View Research, Market Research Future, Fortune Business Insights and P&S Intelligence as published in 2024 to 2026. Product specifications, certification numbers and case results are stated as published by Silver Automation Instruments.