Fog Signal

Operation of Fog Signal at Point of Ayre since 1992

Fog signal discontinued 14:15 hours 12th. August 2005

Fog
Thick mist or cloud of minute water droplets suspended in atmosphere at or near earth's surface
Visibility Detector 2002 Visibility Detector
A pulsed beam is emitted and the back scatter caused by droplets is measured and a signal proportional to droplet density is produced giving a measure of visibility.
When visibility drops below 2 1/2 miles for more then six minutes the fog signal is operated and when visibilty is 2 1/2+ miles for more than six minutes the fog signal is switched off.

Visibility Sensor 2003 Visibility Sensor VF-500-110T
Replaced Visibilty Detector September 2003
An infrared beam is emitted and foward scatter is measured.
When visibility drops below 2 1/2 miles for more then six minutes the fog signal is operated and when visibilty is 2 1/2+ miles for more than six minutes the fog signal is switched off.

Fog Signal Emitter 2002
AGA ELG 300 Emitters.
A coil fed with AC current at 150 Hz.vibrates steel diaphragms to give a 300 Hz.tone.
Two emitters units mounted one above the other,give a nominal range of 4 miles
Showing Visibility Sensor from ground.
Tower-Equipment 2002
Showing front and position of Emitters

Control panels contain equipment to convert 240 Volt AC at 50 Hz.to 150 Hz.
The AC is converted to DC and fed to a transformer where two high current thyristers switch to give a square wave output.This is then taken through a variable transformer to adjust the output level and through a series of power factor correction capacitors to give the optium sound.
Control panels 2008

Two switches.
1-Off/On
2-Automatic/Manual operation
Two meters give Input and Output currents
Two control units for the two emitters which are run as Master and Slave to ensure emitters are synchronised in operation.

Emitter 2002 _________ Emitter diagram 2009

Emitter 2008

Emitter diaphram 2008
Emitter Diaphram 6mm thick Emitter coils 2008
Emitter Coils

Ballast Units 2008 Ballast Units
Used to maintain a steady load to assist circuit stabalisation during non sounding period.

Operation of Fog detector and Fog signal is monitored at NLB's monitoring center.
Technicians visit at least annually to check,modify and update equipment as required.

Northern Lighthouse Board are gradually phasing out Fog Signals the remaining ones due to be discontinued in August 2005
Calf of Man used the Visibility Sensor VF-500-110T operation was similar to Point of Ayre
Fog signal discontinued 14:15 hours 12th. August 2005
Point of Ayre fog signal discontinued 13:15hrs 17th August 2005
Last fog signal Skerryvore discontinued 4th.October 2005

Fog Thick mist or cloud of minute water droplets suspended in atmosphere at or near earth's surface Visibility Detector A pulsed beam is emitted and the back scatter caused by droplets is measured and a signal proportional to droplet density is produced giving a measure of visibility. When visibility drops below 2 1/2 miles for more then six minutes the fog signal is operated and when visibilty is 2 1/2+ miles for more than six minutes the fog signal is switched off.
Visibility Sensor VF-500-110T Replaced Visibilty Detector September 2003 An infrared beam is emitted and foward scatter is measured. When visibility drops below 2 1/2 miles for more then six minutes the fog signal is operated and when visibilty is 2 1/2+ miles for more than six minutes the fog signal is switched off.
AGA ELG 300 Emitters. A coil fed with AC current at 150 Hz.vibrates steel diaphragms to give a 300 Hz.tone. Two emitters units mounted one above the other,give a nominal range of 4 miles	Showing Visibility Sensor from ground. Showing front and position of Emitters
Control panels contain equipment to convert 240 Volt AC at 50 Hz.to 150 Hz. The AC is converted to DC and fed to a transformer where two high current thyristers switch to give a square wave output.This is then taken through a variable transformer to adjust the output level and through a series of power factor correction capacitors to give the optium sound. Two switches. 1-Off/On 2-Automatic/Manual operation Two meters give Input and Output currents Two control units for the two emitters which are run as Master and Slave to ensure emitters are synchronised in operation. _________

Emitter Diaphram 6mm thick	Emitter Coils
Ballast Units Used to maintain a steady load to assist circuit stabalisation during non sounding period.
Operation of Fog detector and Fog signal is monitored at NLB's monitoring center. Technicians visit at least annually to check,modify and update equipment as required. Northern Lighthouse Board are gradually phasing out Fog Signals the remaining ones due to be discontinued in August 2005 Calf of Man used the Visibility Sensor VF-500-110T operation was similar to Point of Ayre Fog signal discontinued 14:15 hours 12th. August 2005 Point of Ayre fog signal discontinued 13:15hrs 17th August 2005 Last fog signal Skerryvore discontinued 4th.October 2005