Model LGA-4000Z

Tunable Diode Laser Gas Analyzer​​​​


Teledyne’s LGA-4000Z series leverages the latest in Tunable Diode Laser Absorption Spectroscopy (TDLAS) to achieve an ultra-fast gas measurement in-line without resorting to extraction and sample conditioning. By tuning the laser to a specific absorption wavelength, based on the gas of interest, the attenuation of the light through a sample cell and the detector can be correlated to the concentration of each g​as, per Beer-Lambert Law.  The laser provides a narrow absorption band which minimizes the effect of interfering compounds in the process.

The System

The LGA-4000Z consists of a transmitter, receiver and connection box. The transmitter drives the tunable diode to emit a laser of a certain wavelength to pass through the environment being measured until it reaches the receiver. The receiver then performs a photo-electrical conversion, signal processing and  spectrum data analysis to obtain the measuring result. The connection box, containing the I/O Interface, makes the connection of the power cable and the signal cable convenient.

Wavelength Modulation Spectroscopy (WMS)

WMS is a method used to significantly increase the sensitivity by reducing the low-frequency noise. The laser light’s intensity is modulated at a high frequency to create a periodic signal to the detector. The signal is then encoded and measured at a high frequency, eliminating the effect of low  frequency noise.​

Gas Detection Parameters


​Min Range

​Max Range

​Detection Limit

​Acetylene (C2H2)

​0-50 ppm


​0.5 ppm

​​Ammonia (NH3)

​0-10 ppm


​0.5 ppm

​Carbon Dioxide (CO2)

​0-1000 ppm


​40 ppm

​Carbon Monoxide (CO)

​0-1000 ppm


​40 ppm

​Ethylene (C2H4)

​0-100 ppm


​1 ppm

​Hydrochloric Acid (HCl)

​0-100 ppm


​0.1 ppm

​Hydrofluoric Acid (HF)

​0-20 ppm


​0.05 ppm

​Hydrogen Sulfide (H2S)

​0-100 ppm


​5 ppm

​Methane (CH4)

​0-200 ppm


​10 ppm

​Oxygen (O2)




​Water/Moisture (H2O)

​0-100 ppm


​​0.1 ppm


  • Flame proof design, IP-66 rated enclosure, ATEX and IECEx Zone 1 IIC T6 Certified

  • Modular design simplifies service and field part replacements​

  • Integral automatic gain control (AGC) algorithm ensure optimal signal integrity

  • Excellent long-term drift characteristics, less than ± 1% FS over 6 months

  • Local OLED display with magnetic buttons to maintain area classification

  • Low power (rated 10W)

  • 2 x 4-20 mA outputs, 2 x alarm relays, RS-485 / RS-232 / GPRS communications



​ATEX and IECEx Zone 1 IIC T6

​Path Length

​Typically 2-65 feet (0.6-20 meters), application-dependent


​± 1% FS


​± 1% FS


​Typically < 1 second (application-dependent)

​Utility Gases

​Air or Nitrogen for purge (application-dependent), 30-115 psig (0.3-0.8 MPa)


​Analog:                      2 x 4-20 mA (isolated), 750 ohm max load
Discrete:                    2 x relay contact, Form-C type, rated 1A @ 24 VDC
Communications:    RS-485 / RS-232


​2 x 4-20 mA (for pressure and temperature compensation)


​24 VDC 10 W


​​-4° to 140°F (-20° to 60°C)