VisGuard - Dust/ Visibility Monitor

Dust/ visibility monitor

The VisGuard measures the scattered light intensity of a sample drawn into the instrument. Filtered purge air is fed through the flow cell, thus enveloping the sample in a protective shroud of clean air. This effectively keeps the optics clean. Installations are either in the tunnel cavity/niches (in-situ) OR alternatively away from the area of measurement extracting the sample from the area through pipes via an external arrangement. An optional sample heater eliminates the influence of any mist effects.


Dust concentration in air, oil mist detection in ship industry, machine & metal industry, visibility monitoring in rail and road tunnels

Features & Benefits

  • Easy to service, high sensitivity, stability and accuracy
  • Easy zero-point checking, even when visibility is poor
  • A special sample flow concept entirely eliminates the danger of flow cell contamination
  • Easy calibration check with checking rod, even at high dust levels
  • Continuous monitoring of visibility using scattered light principle
  • Dual-beam method
  • Operation via local control unit or central multi-channel control unit
  • Installation in tunnel tube or niche
  • Optional sample heater: Choice of measurement with/without fog compensation

  • Nominal range:
    0 .. 100 PLA (Polystyrol-Latex-Aerosols)
    0 .. 3 E/m
  • Scale ranges: 0 .. 15 • 10-3 E/m
  • Protection: IP65
  • Sample temperature: -20 .. +50 °C
  • Sample pressure: max. ±3’000 Pa (±30 mbar)
  • Interfaces:
    RS232 or Profibus DP
    0/4 .. 20 mA
    relay contacts
  • Control unit –
  • Ambient environment:
    Temperature range -20 .. +50°C
    0 .. 100% r.h.
  • Maximum service altitude 3,000 m above sea level
  • Power supply: 85 .. 264 V / 47 .. 440 Hz