Editorial Technical Reference

Sensor Tube/Bypass

This page explains how Sensor Tube/Bypass is classified within Machinery and Equipment Manufacturing. Technical values and manufacturer relationships are research references; confirm the current specification and supplier evidence for each order.

Technical Definition & Core Assembly

A precision component within a Mass Flow Controller that houses the thermal sensor and provides a calibrated flow path for accurate gas measurement.

View Full Specifications Explore Manufacturing Sources
Sensor Tube/Bypass in a manufacturing environment
Representative product image. Confirm appearance and specifications with the manufacturer.

Product Specifications

Technical details and manufacturing context for Sensor Tube/Bypass

Definition
The Sensor Tube/Bypass is a critical internal component of a Mass Flow Controller (MFC) that serves two primary functions: it contains the thermal sensor elements (typically RTDs or thermistors) that measure temperature changes in the gas flow, and it provides a precisely engineered, calibrated bypass channel that diverts a small, representative portion of the main gas flow past these sensors. This arrangement enables the MFC to accurately measure mass flow rates based on the heat transfer principle. The component is manufactured from materials such as Stainless Steel 316L, Hastelloy C-276, or Aluminum, depending on the application requirements. Key parameters include an inner diameter of 1.0–4.0 mm, a length of 50–150 mm, a flow coefficient (Cv) of 0.05–0.5, a helium leak rate of ≤1×10⁻⁹ Pa·m³/s (tested to ISO 27895), a surface roughness (Ra) of 0.2–0.4 μm, an operating temperature range of -20 to 85 °C, an operating pressure range of 0.1–1.0 MPa, a proof pressure of 1.5 MPa, a burst pressure of 3.0 MPa, a material grade of 316L (per ASTM A269), a weight of 0.05–0.2 kg, and a VCR connection type. These values are directory reference ranges and must be confirmed for the specific model and application. The Sensor Tube/Bypass is designed for use in high-purity gas systems where accurate flow measurement is critical. It is essential to verify model-specific values and standards with the legal manufacturer or supplier before procurement or installation.
Working Principle
A small, controlled fraction of the main gas stream is diverted through the bypass channel within the sensor tube. The thermal sensor elements measure the temperature difference between an upstream heater and downstream points. As gas flows through the tube, it carries heat away, creating a temperature differential proportional to the mass flow rate. This differential is converted into an electrical signal for flow measurement and control.
Common Materials
Stainless Steel 316L, Hastelloy C-276, Aluminum
Technical Parameters
ParameterTypical rangeNotes & selection driver
Inner Diameter1.0–4.0 mmDetermines flow capacity and sensor response.
Length50–150 mmAffects thermal sensor placement and response time.
Flow Coefficient (Cv)0.05–0.5 CvDefines flow capacity for given pressure drop.
Leak Rate≤1×10⁻⁹ Pa·m³/sHelium leak test; critical for gas purity.ISO 27895
Surface Roughness (Ra)0.2–0.4 μmSmooth finish minimizes particle entrapment and flow disturbance.
Operating Temperature-20–85 °CExceeding range may affect sensor accuracy and material integrity.
Operating Pressure0.1–1.0 MPaBelow 0.1 MPa the sensor may not receive adequate flow.ISO 5208
Proof Pressure1.5 MPaMaximum pressure without permanent deformation.ISO 5208
Burst Pressure3.0 MPaSafety limit; must not be exceeded.
Material Grade316LCorrosion-resistant stainless steel for high-purity gases.ASTM A269
Weight0.05–0.2 kgAffects handling and installation.
Connection TypeVCRMetal gasket seal for leak-tight connections.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM
  • Sensor Tube Body Part
    Forms the main structural housing and primary flow path for the bypass gas.
    Material: Stainless Steel
  • Thermal Sensor Elements Part
    RTDs or thermistors that measure temperature changes in the gas flow for mass flow calculation.
    Material: Platinum/Tungsten
  • Bypass Channel Orifice Part
    Precision orifice or laminar flow element that meters and stabilizes the gas flow through the bypass.
    Material: Stainless Steel
  • Seals/Gaskets Part
    Ensure leak-tight connections between the sensor tube and the main MFC body.
    Material: Viton/Kalrez
  • Heater
    Puts heat into the gas stream; the flow reading is the temperature difference it creates.

Application & selection

Application Fit & Sizing Matrix

Operational Limits
pressure: 0 to 100 psig
flow rate: 0.1 to 1000 sccm
temperature: -20°C to 80°C
slurry concentration: Not applicable - designed for clean gases only
Media Compatibility
✓ Inert gases (N2, Ar, He) ✓ Corrosive gases (Cl2, HCl) with compatible wetted materials ✓ Reactive gases (H2, O2) with proper safety protocols
Unsuitable: Particulate-laden or slurry media - risk of sensor fouling and flow path obstruction
Sizing Data Required
  • Required gas flow range (sccm or slm)
  • Gas type and chemical compatibility requirements
  • Process pressure and temperature conditions

Risk, maintenance & compliance

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause
Abrasive erosion
Cause: High-velocity particulate flow causing gradual material loss on inner surfaces, often from contaminated process fluids or inadequate filtration
Cavitation
Cause: Rapid pressure changes causing vapor bubble formation and collapse, typically from improper system design, excessive flow velocity, or temperature fluctuations
Maintenance Indicators
  • Audible high-frequency whistling or hissing indicating flow restriction or bypass leakage
  • Visible external corrosion, pitting, or discoloration at connection points suggesting internal degradation
Engineering Tips
  • Implement regular ultrasonic thickness testing to monitor wall erosion and schedule preventive replacements before failure
  • Install proper flow straighteners and maintain optimal fluid velocity (typically 3-6 ft/sec) to minimize turbulence-induced damage

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards
ISO 4401:2005 (Hydraulic fluid power - Four-port directional control valves - Mounting surfaces) ANSI/ASME B16.5 (Pipe Flanges and Flanged Fittings) DIN 3852-2 (Connections for fluid power systems and general use - Part 2: Test methods for connections with elastomeric seals)

Quoted from the published standard.

Manufacturing Precision
  • Bore diameter: +/-0.02mm
  • Surface finish (Ra): 0.8μm maximum
Quality Inspection
  • Helium leak test (per ASTM E499/E499M)
  • Pressure decay test (per ISO 19879)
Technical documentation
Request current drawings, revision history, and a signed specification sheet.
Manufacturing capability
Verify equipment lists, process limits, capacity, and representative production evidence.
Inspection readiness
Confirm test methods, calibrated equipment, sampling plans, and traceable reports.
Supplier transparency
Check the legal entity, factory address, ownership, certifications, and direct contacts.

Compare the published product scope and source details, then include your specifications and quantity in an enquiry.

Manufacturers of Sensor Tube/Bypass

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Greenough Enterprises Co., Ltd.
Shenzhen, Guangdong, CN
Also makes: LED Smart Lighting, LED Illumination Array, Motion Sensor
Listed on the company's own website · profile compiled by CNFX from public sources
Listed there as: “PIR sensor tubes”
View source page ↗ greenoughled.com · recorded 2026-09-18
View profile Send enquiry

Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.

Buyer enquiry

Request manufacturing insight for Sensor Tube/Bypass

Ask for use case, specification boundaries, supplier type, and RFQ preparation information for this product.

Where it goes
Straight to the CNFX editorial desk, and to the manufacturer if this product is linked to a claimed profile. Nothing is broadcast to a supplier list.
Your details stay here
We do not sell or rent enquiry data, and we do not add you to a mailing list. Used only to answer this request.
No commission, no middleman
CNFX is a directory. We take no cut of any order and never negotiate on a supplier's behalf.
What to include
Share your product specifications, quantity, destination and target delivery date.

Your business information is used only to process this request.

Thank you! Your message has been sent. We'll respond within 1–3 business days.
Sorry, we couldn't send your message. Please try again, or email us at [email protected].

Frequently Asked Questions

What is the function of the sensor tube/bypass in an MFC?

It houses the thermal sensor elements and provides a calibrated bypass channel that diverts a small portion of the gas flow past the sensors, enabling accurate mass flow measurement based on heat transfer.

What materials are available for the sensor tube/bypass?

Common materials include Stainless Steel 316L, Hastelloy C-276, and Aluminum. The choice depends on the gas compatibility and application requirements.

What are the key specifications to verify before purchasing?

Verify inner diameter, length, flow coefficient (Cv), leak rate, surface roughness, operating temperature and pressure, proof and burst pressures, material grade, weight, and connection type. Always confirm with the manufacturer for your specific model.

How is the leak tightness of the component ensured?

The component is helium leak tested to a maximum leak rate of ≤1×10⁻⁹ Pa·m³/s, per ISO 27895. This ensures high gas purity and system integrity.

Data basis: editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Related equipment

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Mass Flow Controller
View system integration details

Industrial Ecosystem & Supply Chain Structure

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Sensor Tube/Bypass.

sensor tube

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review · Page last updated 13 October 2026

Need to Manufacture Sensor Tube/Bypass?

Compare manufacturer profiles with relevant product and process capability.

Create Manufacturer Profile Contact Us
Previous Product
Sensor Interface Module
Next Product
Separation Bowl
Get QuotesChat