ABB MEASUREMENT & ANALYTICS | DATA SHEET LS4000 Diode laser analyzer

Introduction

Application and design

The LS4000 is an in situ cross-duct analyzer for measuring gas component concentrations. It applies the highly selective optical measuring principle of tunable diode laser (TDL) ab sorption spectroscopy.  

The LS4000 is a stand-alone system which consists of a transmitter unit with a laser light source and a receiver unit with a photodetector.

Both units are mounted opposite each other on the process pipe or stack and are connected by a junction box.

Measuring principle – TDLAS

The LS4000 employs the optical measuring technique of absorption spectroscopy, which utilizes the fact that a specific gas absorbs specific light wavelengths.  

The light beam is emitted from a tunable laser diode located in the transmitter unit. The laser light passes through the process gas and strikes the photodetector in the receiver unit. The measured gas component present in the optical path absorbs the laser light, attenuating the light received.

A sophisticated signal algorithm processes the amount of light attenuation and calculates the gas concentration on the basis of the Beer-Lambert law. The influence of temperature and pressure variations is eliminated by dynamic automatic correction.

Specification

Measurement components and measurement ranges

Measurement range quantity 1 physical measurement range per sample component,   1 x transmission

NOTICE

• The analyzer performance characteristics have been determined according to IEC 61207-1:2010 “Expression of performance of gas analyzers – Part 1: General”. They are based on nitrogen as the associated gas. Compliance with these characteristics when measuring other gas mixtures can only be assured if their composition is known. 

 • All specifications refer to an optical path length (OPL) of 1 meter, tested in ABB’s test and calibration jig. However, application-dependent variations may occur. The specific detection limit, minimum and maximum measurement range for a specific application will depend on the gas conditions (pressure, temperature and gas composition) and optical path length. Minimum measurement range, maximum pressure and maximum temperature cannot necessarily be realized simultaneously under all conditions. • The maximum pressure and maximum temperature given are physical (spectroscopic) limits. 

 • Applications exceeding the above given spectroscopic limitation might be possible on request.

Stability Performance data below is given at standard conditions. Data may vary depending on the specific application.

Influence effects 

 For large variations of process temperature and pressure, LS4000 applies an automatic dynamic correction which requires 4–20 mA inputs. Influence effects and necessity for temperature or pressure sensor depend on the specific application and are defined by ABB.

Dust load Instrument remains operable if transmission loss < 97 %.

Accompanying gases/cross sensitivity No cross sensitivity within normal operation conditions.

Flow effect No effect on the measurement, but the flow will determine the amount of gas needed for process purging.

Ambient temperature In permissible range: no effect

Dynamic response Warm-up time < 5 min Response time Typically 5 sec

Maintenance interval and calibration/validation Maintenance interval Depending on application and dust load

Calibration Single point calibration with test gas and an external off-line calibration cell (see Accessories on page 7).

Calibration/validation interval Depending on application, typically once a year

Process purging   Depending on the application, purging on the process side is typically necessary. It is not required to purge the instrument housing.

Available flange size DN 50 / PN 10, ANSI 2 in.-150 lb, JIS 10K 50A

Material Flanges: AISI 304 (1.4301), standard AISI 316L (1.4404), optional O-rings (process): FPM (standard), FFKM

Weight 3,1 kg

Gas port for purging 1/4 in. Swagelok connectors for tubes with 8 mm outer diameter.

Purging medium Instrument air (dry and oil-free, compliant with standard ISO 8573.1, Class 2–3) or nitrogen (depending on the application)

Electrical interfaces Analog outputs Up to three 4–20 mA outputs (one for each measurement component and transmission), working resistance max. 500 Ω, not isolated

Analog inputs Up to two 4–20 mA inputs for dynamic process temperature and pressure correction, working resistance max. 100 Ω, not isolated

Digital outputs Up to two digital outputs, 1 A at 30 V DC/AC, NO, for error and gas alarm

Service port Ethernet

See page 8 for connection drawing.

Installation location

The measurement gas must be well stirred at the selected location to produce a representative measurement result. Stratification in the measurement gas path results in erroneous measurement.