TLS-420/S & TLS-420/SW

The Hagner TLS-420 Tunnel Entrance Photometer is designed to measure the average luminance of road tunnel entrance and its surroundings according to CIE recommendations and is used, together with a PLC/computer, to regulate the lighting inside the tunnel. The idea is to control the illumination inside the tunnel to a level corresponding to the degree of light adaptation of an approaching cardriver´s eyes.



The aim of road tunnel lighting is to ensure that traffic, both during daytime and nighttime, can approach, pass through and leave a tunnel, at the designated speed, with a degree of safety and comfort not less than along the adjacent stretches of open road.

In daytime it is essential that appropriate luminance has been provided in the threshold zone (the first stretch of the entrance) of the tunnel to avoid the driver experiencing ”the black hole effect”. A hazardous situation is created if a lack of visibility suddenly causes the driver to reduce speed. The required luminance depends on the luminance to which the approaching car driver’s eyes are adapted. Studies show that to a large extent this adaptation depends on the luminance in and around the tunnel entrance.

According to CIE (Commission Internationale de l’Eclairage) recommendations this luminance can be measured as the luminances contained in a conical field of view, subtending an angle of 20° It is normally recommended that the measurement is made at a distance from the tunnel entrance which is equivalent to the stopping distance for a vehicle approaching the tunnel.

(I.e. the distance depends on factors such as the speed on the road, its slope, its condition etc). Other factors can also influence the measuring distance. (For further information see CIE publications No 61 (1984) and No 88 (1990).)

The Hagner TLS-420 Tunnel Entrance Photometer is designed to measure the average luminance of a tunnel entrance and its surroundings as to CIE recommendations. The photometer measures the average luminance within a cone with a top angle of 20°(other measuring angles can be provided on request), by means of a detector carefully filtered to give a spectral response close to that of the human eye, as defined in CIE standards.

The photometer has an output of 4 - 20 mA DC for a luminance range 0 - L cd/m² where ”L” is chosen by the customer when ordering the photometer. A common value of ”L” is 6,500 cd/m²

The 4 - 20 mA output makes the TLS-420 suitable for computerized systems and also makes it possible for the output signal to be transmitted over great distances. (Max external resistance is 800 ohm.)

As an important part of the system B Hagner AB offers a ready programmed PLC computer for regulating the tunnel lighting, with switching levels (up to 10 levels each for 2 separate Tunnel Photometers plus 2 alarm levels) and time delays set according to the customers requirements. When delivered with a Display Panel the customer can easily change the preset values, if required.

The Photometer is mounted in a waterproof, thermostated housing made in stainless steel. The front glass can be provided with automatic cleaning equipment. The power supply is 220 - 240V AC.


When delivered the photometers are carefully calibrated to the measuring range specified with the order. The basic light sensitive component in the Tunnel Photometers is a very long time stable silicon photo diode. Under normal use a calibration interval of several years should be quite sufficent. (Please see also ”Maintenance” below.) Calibration can be made by the manufacturer, B Hagner AB in Sweden, or by official test laboratories, equipped for calibration of luminance meters.


When provided without washer and wiper:

- As measurements are taken through the front window of the photometer, the outside of the window should be regularly cleaned. How often this must be done depends on the position of the photometer and the surrounding environment, i.e. how soon the window becomes dirty. Empiric studies at sight are recommended.

When provided with washer and wiper:

- The water tank shall be filled at regular intervals. The length of the intervals depends on how often the washer is used and for how long each time.

- The wiper blade (the rubber) should be regularly checked so that it is not worn out. Control intervals depend on climate and environment but even in fairly rough environments an initial interval of 2-3 years is normally sufficient. Eventually the length of the intervals may be reduced until the wiper blade has been exchanged.

Overvoltage protection

In certain areas where the Hagner Tunnel Entrance Photometers are mounted there is risks from overvoltage and/or transients on the power net and transients on the signal cable; Over-voltage, for instance due to an unstable power supply and transients, mostly due to lightning strikes in the surrounding area. Both incidents can, if they are powerful, damage the electronics in a Photometer. (The instruments are provided with VDRs but these give only a very limited protection.) It is therefore recommended that Photometers, mounted in such areas, are con-nected to overvoltage protection which will greatly reduce the risk for damage.

For further information, see separate leaflet Hagner OVP-02 Overvoltage Protection

Technical data

Detector: Silicon photo diode, Vλ-filtered.
Measuring angle: 20°(as standard), spectral angles on request
Measuring range: Specified with order, e.g. 0 - 6,500 cd/m²
Accuracy: Better than +/-3%
Spectral deviation f'1: Better than 5%
Output signal: 4 - 20 mA DC
External resistance: max 800 ohm
Temperature range: -30ºC / +70ºC
Housing: Stainless steel type 316 (SS2348) powder coated
Protection rate IP 65
Power supply: 220 - 240V AC 24VA
Heater: 6W (PTC heating)
Dimensions: 460 x 155 x 170 (220) mm
Weight: 6.0 kgs - 6,6 kgs with built-in wiper
Mounting: On adjustable mount or wall bracket.
Models: TLS-420/S Without wiper
TLS-420/SW With built-in wiper
Accessories: WP10 Windscreen washer
SW/S Adjustable mount
CSS-1 Wall bracket
OVP-02 Over voltage protection
EH-150 PLC computer inclusive of program
Sight 400 for TLS-420/S and TLS-420/SW

Modbus option

The TLS420 can be ordered with RS-485 Modbus option. Digital measurement value can be obtained on the RS-485 bus. Extra optional abitity to control washer, wiper and washer fluid level. Contact hagner customer service for additional digtal order form.

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