TDLAS · OEM Gas Measurement Modules

Your instrument needs a measurement node that works in the field.

Not a lab prototype. Not a full analyser. A compact, calibrated TDLAS module that plugs into your device and delivers reliable gas concentration data — from day one.

Start Project Assessment How TDLAS works →
±2%
Full-scale accuracy
Line A module
20 kPa
Min. operating pressure
Line B pipeline probe
5 ppm
Detection limit
CH₄ standard conditions
TDLAS measurement chain: DFB laser source, absorption cell, photodetector, 2f/1f WMS signal processing
What Specvaltech does

We supply TDLAS gas measurement modules to OEM instrument manufacturers and system integrators.

Specvaltech designs and manufactures Line A (compact OEM, ±2% FS, 0–100% CH₄) and Line B (pipeline insertion, 20–200 kPa abs, Ex ia I Ma target) modules based on Tunable Diode Laser Absorption Spectroscopy. We are a component supplier — you integrate our module into your instrument; we handle the measurement physics, calibration, and field reliability.

The real problem

Why instrument makers choose a dedicated TDLAS module

Building gas measurement into your instrument from scratch means solving physics, optics, signal processing, and field certification — all at once. Most teams run into the same six walls.

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Lab accuracy doesn’t survive the field

Vibration, temperature swings, and condensation degrade optical alignment and baseline stability. NDIR sensors drift. Electrochemical cells age. Your warranty claims multiply.

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Negative-pressure environments break conventional sensors

Coal mine drainage headers, biogas digesters, and vacuum extraction lines run at 20–80 kPa absolute. Most sensors are rated for positive pressure only. Sampling pumps add complexity and failure points.

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OEM integration takes 12–18 months

Sourcing a DFB laser, TEC controller, absorption cell, and 2f/1f lock-in amplifier separately — then integrating them — consumes engineering time that should go into your product’s core value.

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Certification is a moving target

Ex ia I Ma (intrinsic safety, Group I, Category Ma) requires entity parameter documentation, barrier coordination, and type examination. Getting this wrong delays market entry by 6–12 months.

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Gas-specific selectivity is hard to achieve

Cross-sensitivity to CO₂, H₂O, and other hydrocarbons corrupts CH₄ readings. NDIR broadband absorption cannot distinguish overlapping spectral lines without expensive optical filters.

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No consumables — but still needs calibration

Customers expect zero-maintenance operation. But without a structured calibration protocol and baseline drift correction, “no consumables” becomes “no confidence in readings.”

Who we work with

Three types of organisations that integrate our modules

We are a component supplier, not a system house. Our customers are the people who build instruments, integrate systems, or operate infrastructure at scale.

OEM Instrument Maker

You manufacture gas analysers, safety monitors, or process instruments

You need a measurement node that fits your enclosure, speaks your protocol (UART / Modbus / 4–20 mA), and arrives calibrated. Line A is designed for this.

System Integrator

You build monitoring systems for mines, pipelines, or industrial plants

You need a sensor that survives the installation environment — negative pressure, vibration, explosive atmosphere — without a sampling pump or conditioning system. Line B is designed for this.

R&D / Procurement

You are evaluating TDLAS technology for a new product platform

You need technical documentation, entity parameters, and a sample unit before committing to a production order. We support evaluation with full specification disclosure and application engineering.

Beer-Lambert law diagram: laser intensity attenuated by gas absorption proportional to concentration and path length
Why TDLAS — not NDIR, not electrochemical

The measurement physics that makes field reliability possible

TDLAS uses a single-frequency DFB laser tuned to a gas-specific absorption line. The result is a measurement that is inherently selective, drift-resistant, and free of consumables.

1

Single-line selectivity

The laser wavelength is locked to one absorption line of the target gas. CO₂, H₂O, and other hydrocarbons cannot produce false positives — their lines are at different wavelengths.

2

2f/1f normalisation eliminates baseline drift

Wavelength modulation spectroscopy divides the second-harmonic signal by the first-harmonic carrier. Laser power fluctuations and window contamination cancel out of the ratio.

3

Direct-path measurement — no sampling pump

Line B uses a probe inserted directly into the pipeline. Gas flows past the optical path naturally. No pump, no filter, no moving parts in the measurement chain.

4

No consumables, 5-year calibration interval target

No electrolyte, no membrane, no reference gas cylinder. Calibration drift is dominated by optical path length stability — a mechanical parameter, not a chemical one.

Full TDLAS technology page →
Two modules, two integration scenarios

Choose the module that fits your installation

Line A and Line B share the same TDLAS measurement core. They differ in form factor, pressure range, and integration interface — to match the two most common OEM scenarios.

Line A OEM compact TDLAS module schematic: 140x110x96mm enclosure, DFB laser, 10cm absorption cell, RS485/4-20mA output
Line A · OEM Compact

For instrument enclosures and portable analysers

A self-contained TDLAS measurement node with a 10 cm absorption cell, integrated DFB laser and TEC, and a calibrated digital output. Designed to be embedded inside your instrument — not bolted on the outside.

Gas target
CH₄ 0–100% vol
Accuracy
±2% FS
Detection limit
5 ppm
Output
UART · Modbus · 4–20 mA
Power
3.3 V / 5 V DC
Pressure
80–120 kPa abs
Line A full specifications →
Line B pipeline insertion TDLAS probe: direct-path measurement, 20-200kPa absolute, Ex ia I Ma target certification
Line B · Pipeline Insertion

For negative-pressure pipelines and extraction headers

A probe-style TDLAS module that inserts directly into the pipeline. Operates at 20–200 kPa absolute — covering the full range of coal mine drainage headers and biogas extraction systems. No sampling pump required.

Gas target
CH₄ 0–100% vol
Accuracy
±3.5% FS
Pressure
20–200 kPa abs
Cert. target
Ex ia I Ma
Installation
Direct insertion
Output
Modbus RTU · 4–20 mA
Line B full specifications →
Where our modules are deployed

Application scenarios with documented measurement requirements

Each application has specific pressure, accuracy, and certification requirements. Our modules are specified to match — not adapted from a general-purpose sensor.

Underground main roadway gas drainage: TDLAS measurement node at main header, 20-80 kPa abs

Coal mine — underground main roadway drainage

CH₄ monitoring at the main drainage header. Pressure: 20–80 kPa abs. Safety interlock threshold: 30% LEL typical. Line B direct insertion, no pump.

See full application →
Pump station monitoring: TDLAS module at extraction pump inlet, 40-120 kPa abs

Pump station — extraction pump inlet

Monitoring at the pump inlet to protect equipment and verify extraction efficiency. Pressure: 40–120 kPa abs. Fast response (<10 s T90) for pump interlock.

See full application →
Branch manifold monitoring: TDLAS at individual seam connections, 20-60 kPa abs

Branch manifold — per-seam concentration

Per-branch measurement to identify high-yield seams and detect dilution. Pressure: 20–60 kPa abs. Multiple points require compact, low-cost modules.

See full application →
Gas utilisation monitoring: TDLAS quality check before combustion engine or CNG compression

Utilisation — quality before combustion or compression

CH₄ purity verification before combustion engine or CNG compressor. Pressure: 80–200 kPa abs. Accuracy: ±2% FS for fuel-value billing.

See full application →
How a project works

From application brief to production module in four steps

1

Application brief

You describe your gas, pressure range, accuracy requirement, and integration interface. We confirm module fit or flag a mismatch.

2

Specification lock

We issue a formal specification sheet with entity parameters, interface drawing, and calibration certificate format.

3

Sample & integration

We ship a sample module with integration documentation. Your team integrates and validates against your instrument’s requirements.

4

Production supply

Series production with batch calibration certificates. We support your type examination with entity parameter documentation.

Technical resources

Engineering articles for instrument designers

All articles →
Technology

TDLAS vs NDIR: Which technology belongs in your OEM instrument?

A side-by-side comparison of measurement physics, drift behaviour, cross-sensitivity, and OEM integration cost for CH₄ detection applications.

Read article →
Application

Measuring CH₄ in negative-pressure pipelines: what changes below 80 kPa?

Pressure correction, sampling system design, and why direct-path TDLAS eliminates the pump problem in coal mine drainage applications.

Read article →
Integration

OEM integration checklist: 12 questions before you commit to a TDLAS module

Interface protocol, power budget, optical path contamination, calibration interval, and entity parameter coordination.

Read article →
Start here

Tell us your application. We’ll tell you which module fits — and why.

We don’t send a product catalogue. We review your gas, pressure, accuracy, and integration requirements and give you a specific module recommendation with entity parameters.

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Module fit confirmation — Line A or Line B, with reasoning based on your pressure range and installation type.

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Accuracy budget check — We calculate the expected error band at your operating conditions, including pressure correction.

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Integration interface confirmation — Protocol, power, and mechanical fit against your instrument’s requirements.

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Certification path — If you need Ex ia I Ma, we outline the entity parameter documentation we provide for your type examination.

Direct contact

Senior Engineer Zhao

Application engineering & OEM integration

📱 WeChat / Mobile: +86 189 7107 8447

💬 WhatsApp: +86 189 7107 8447

✉ engineer.zhao@specvaltech.com

7×24 Service Hotline

Doctor Zhao

info@specvaltech.com

Project Assessment Request

We respond within 1 business day with a module recommendation and accuracy budget estimate.