Tunnel safety relies on accurately measuring luminance – the perceived light available for drivers to drive safely – the main control variable for the tunnel lighting.
Features
- The JES Photometer measures luminance in the:
- Access zone L20 (acc. CIE 88:2004)
- Threshold zone Lth
- Interior zone Lin
- Zoom lens to adjust the focus areas
- Sensor with V(λ) filter and silicon photo element
- Temperature compensated and long term stable amplifier for the photoelectric current using live zero
- Heated housing with protection class IP65 either made of poly-carbonate or stainless steel 1.4571
- Electronically controlled heating and temperature monitoring
- Mounting flange to adjust horizontal and vertical angle
- Fault indication by relay isolated contact (NC)
- Optional second output channel for increased resolution at low lighting levels
- Surge protection.
System Set-up
- Photometer in camera housing (Luminance camera) mounted on the tunnel wall or a pole in front of the tunnel portal
- Power supply (230 or 115 VAC)
- Signal outputs connected to lighting control system or tunnel control system
Operation
The requirements for tunnel lighting are determined by the nature of the human eye. How well the eye recognises vehicles and other obstacles in a tunnel depends on the lighting and visibility as well as the reflection characteristics of the road surface and the tunnel walls. Tunnel lighting needs to be adapted to these environmental conditions.
The tunnel lighting must be controlled so that users, both during the day and by night, can approach, pass through and exit the tunnel without changing direction or speed with a degree of safety equal to that on the approach road. Especially the lighting of a tunnel entrance should be adequate to avoid the “black hole effect” when a driver enters the tunnel.
Luminance is the measure representing what a human being perceives as brightness and as such is the main control variable for the tunnel lighting.
The luminance photometer comes with a zoom lens that is focused to measure the relevant area. Light from this area through the lens is directed to the photo element detecting its intensity. The integrated evaluation unit then calculates the luminance and provides it through the analogue output(s).
Advantages
- Specifically developed for application in tunnels
- No control unit required
- Easy configuration
- Corrosion resistant against aggressive tunnel atmosphere
- Sensors can be replaced quickly with no tools and no re-alignment required
- Minimised spare requirements
- Extremely low maintenance requirements.
