Lightning is an ongoing concern in regards to personnel safety in the workplace. This is especially true in a work environment such as the open structure of the GBT. During the Spring and Summer months in our area of the United States fast moving thunderstorms can present such a hazard. While it is part of the operator's duties to maintain a watchful eye on the weather, it is difficult to know when a thunderstorm will directly impact ongoing maintenance. For this reason three different lightning detection systems are being used during maintenance days at the telescope. This document will provide basic knowledge of the three systems. For detailed operating instructions refer to the Operations Procedures part of this manual.
There is a detector in the warehouse at the GBT that was built by "in-house" engineers and technicians. This design was based on readily available circuits and components. The function of the detector is to measure static electric potential in the nearby atmosphere. It does this with the aid of an antenna mounted on top of the tower outside of the warehouse.
Currently the control box resides in the operator's office at the warehouse. Over time some of the controls have been disabled. The "ON" switch should always be in the on position. The operator can check functionality by pressing the "Test" button and once an alarm sounds it can be silenced with the appropriate button.
StrikeAlert is a lightning detector that provides an early warning of approaching lightning strikes from as far away as 40 miles and lets you know if the storm is coming your way. Its designed for personal and portable use.
An audible alarm sounds when there's a strike and a corresponding LED light illuminates accordingly at lightning distances of 20-40 miles, 12-24 miles, 6-12 miles and within 6 miles.
The detector is housed in a small pager-like casing that can be clipped on a belt loop and runs on a single AA battery up to 100 hours.
The Boltek LD-250 Lightning Detector puts a live lightning map on your laptop or desktop computer. Within milliseconds of a lightning strike the detector beeps and your computer displays the strike location. The LD-250's direction-finding antenna measures lightning strike direction while the LD-250's receiver estimates distance from received signal strength. Advanced signal processing in software improves distance accuracy, reducing the effects of strike-to-strike variations in strike energy.
The LD-250 display is resizable like any other Windows application. A small graph depicting strikes / noises per minute is selectable through the "Display option on the menu bar.
The parameters of how strikes are displayed and handled are changed through the "Configure" menu option on the menu bar. Under this selection the following parameters can be configured:
Strike Display
Strike persistence
New Strike Flags
New Strike Flag Persistence
Looping Display
Loop Duration
Loop Speed
Close Alarm
The software will notify you if a strike occurs within a predefined distance. On gbtops it will display a warning box along with a predefined sound (if configured) and if it is being viewed remotely one will only get the warning box.
Enabled / Disabled
Mute
Popup Notification Window
Alarm At (miles)
Enable Software Alarm (configured in number of strikes in number of minutes)
Severe Storm Alarm
Enabled / Disabled
Mute
Popup Notification Window
Enable Software Alarm (configured in number of strikes in number of minutes)
100 Mile Screen (These same parameters are configurable for the 200 and 300 mile maps)
Distance Rings (option)
Label Rings (option)
Crosshairs (option)
Heading Indicator (option)
Invert BMP Colors (Allows inversion of the colors of the background map)
Number of Range Rings
Miles / Kilometers selection
Map file directory location
Strike Processing
Receiver Squelch (to reduce the number of noise strikes)
Log Limit (to set a top number of strikes per minute to reduce lags in the strike display)
Receiver Enabled On (to choose which Com port the receiver feeds in to)
Keep Data Files (Optional to keep old log files or not)
Sound
This panel has areas for selecting sounds for various events. It also presents the options for beeping the computer speaker and what volume level you wish for it to beep at.
The LD-250 can warn of both close and severe thunderstorms. If a storm is detected closer than a preset distance or the strike rate exceeds a preset limit, the LD-250 sounds its internal alarm and activates the computers alarm tone or WAV file notification if enabled.
Strike rates, both Close Strikes per Minute and Total Strikes per Minute are shown for the previous hour on the Strike Rate Trend Graph letting you easily see if storms are increasing in severity or dying off.
Three display ranges, 100, 200 and 300 miles (160, 320 and 480 km) allow you to zoom into the region of interest. Zoom out to the maximum range of 300 miles (600 miles across) or zoom in to 100 miles to see only the nearby storms.
www.boltek.com
www.strikealert.com
Prepared by: Eric Knapp, Operator
Last Modified: 25MAR03