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LaserDust^TM Monitors

The LaserDust monitors are designed for measurement in stacks and other cross-duct applications. For long distance measurement of dust concentrations refer to the DM4 Open Path Dust Monitor section.

The LaserDust Medium Path (MP), Long Path(LP) and Extra Long Path (XLP) monitors are compact, high performance dust monitors for continuous in-situ measurement of dust concentration or opacity. Based on well-proven diode laser technology the instruments have a number of unique features.

Features

Response time down to one second
Dust pulse detection with 50 ms resolution
Very low detection limit (0.5 mg/Nm3)
High dynamic range
Scattered light detection for low dust levels
Low cost of ownership
Ethernet connection (optional)

The monitors' very compact design comprises a transmitter and receiver unit, only. Both are protection classified to IP66 for outdoor use. Measurement readings are provided through standard 4-20mA current loops, a fibre-optic output or the optional Ethernet connection. The latter enables communication via a local area network or the Internet.

Measuring principle

The LaserDust's optical measuring principle is based on the property of particles to absorb and scatter incident light. Red laser light is transmitted through the process gas and two separate detectors located opposite the laser detect the amount of direct light transmitted and the amount of forward scattered light. Both signals depend on the number of dust particles present. At low dust levels (< 200 mg/Nm3) concentration is calculated from the scattered light signal, which provides a precise measurement down to 0.5 mg/Nm3 and is unaffected by dust depositing on the windows. At high dust levels concentration calculation is based on the light absorption signal, which provides virtually unlimited dynamic range (at least 10 g/Nm3). Alternatively, this signal can be used for measurement of opacity (see Technology for more information).

Installation and Operation

The LaserDust monitors are easy to install and designed to operate in very rough industrial environments. The transmitter and receiver units are mounted directly onto the duct or stack flanges. For installation in hazardous areas an ATEX approved EEx P solution is available. The instrument contains no moving parts, thereby limiting preventive maintenance to visual inspection and cleaning of optical windows. Purging with instrument air prevents dust from fouling the optical windows. Upon installation in-situ calibration against an extractive reference method is important to ensure that different types of dust with different optical properties are measured correctly.

Data sheet for download

LaserDust Medium, Long and Extra Long Path (Acrobat 242933 bytes)(.pdf)

Updated 2007-02-05

NEO Monitors is a subsidiary of Norsk Elektro Optikk A/S