Optical Scientific Inc. (OSi)

- Model WSS-300-DS - Tunnel Wind Speed Sensor and Smoke Sensor



OSi's patented Wind Speed and Smoke Sensor (WSS™) makes drift free air flow measurements across the tunnel, calculates true average wind speed, and detects smoke. The WSS-300-DS model is equipped with Automatic Gain Control (AGC) to compensate for variations in opacity caused by particulate matter, smoke, or moisture suspended in tunnel. The WSS-300-DS uses OSi patented optical scintillation technology. The optical scintillation technique relies on advanced Digital Signal Processing (DSP) electronics to 'see' and measure the movement of turbulence found in a tunnel air flow and provides highly accurate, path-averaged wind speed measurements.

Unlike ultrasonic flow sensors the WSS-300-DS measures true average wind speed across the tunnel and detects smoke in the optical path. The WSS-300-DS is perfect for tunnel ventilation monitoring and smoke detection.

The WSS-300-DS consists of DSP / multiprocessor - based control unit teamed with a set of optical transmit and receive heads. The heads are easily installed on opposite sides of a tunnel above the expected height of vehicles. The transmit head sends a visible diverging light beam directly across and perpendicular to the flow.


The control unit processes the scintillation detected by the receiver, displays the flow data locally and transmits it to a PC, PLC, DAS or other data collection device that accepts a serial data link and/or a 4-20 mA current loop. The control unit can be configured from either the local keypad and display, or from a laptop or portable terminal.

Applications Include traffic tunnels, rail tunnels, and mine tunnels.

Performance Specifications

  • Measurement Technique: Optical Scintillation (OSi Patented)
  • Dynamic Ranqe: ±40 m/s
  • Accuracy: ± 0.1 m/s or ± 2% of readinq, whichever is qreater
  • Repeatability: ± 0.1 m/s or ± 1% of reading, whichever is greater
  • Long Term drift: Less than 1 % per year
  • Response Time: 3 to 600 seconds, user selectable
  • Automatic Calibration Check: 2 or 3 point; user selectable interval- or- on external command
  • Sensor Health Monitoring: Continuous self-test of voltages, performance, optics, etc.
  • Smoke Detection: Optical


  • Tunnel Diameter: 30 - 100 ft standard - - consult factory for other ranges
  • Ambient Temperature: -40 to+60 °C (-40 to 140 °F)
  • Humidity: 0-100%

Light Source

  • Liqht Source: Eye safe visible red LED
  • Wave Length: 670 nm
  • Divergent angle: 5°


  • Transmit Head: 9x9x 13 inches; 13 lbs; NEMA 4X
  • Receive Head: 9x9x13 inches; 13 lbs; NEMA 4X
  • Control Unit:
    • Rack Mount Version (standard): 5 x 17 x 20 inches, 13 lbs. (for indoor use)
    • NEMA4 Wall Mount (optional): 12x16x10 inches, 15 lbs. (for outdoor / equipment floor use)

Electrical Specification

  • User Interface:
    • RS-232 serial I/O and / or 4-20 mA optically isolated current loop
    • Relay contacts for fault alarm and calibration check initialization.
  • Power for Transmit Head: Universal 100-240 VAC. 50/60 Hz, 12 VA (fused & surge protected)
  • Power for Control Unit: Universal 100-240 VAC. 50/60 Hz, 40 VA (fused & surge protected)
  • Cable between Control Unit & Receive Head: Up to 300-DS ft (shielded. 10 conductor, 22 AWG)

(Specifications subject to change without notice.)

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