Sensor Technology

Advanced Lightning Sensor

The LPS-200 Advanced Lightning Sensor with Digital Signal Processing is designed to bring the latest technology and precision to the market today. Offering LF/VHF dual-band operation, the LPS-200 processes lightning strokes from both cloud-to-ground (CG) and cloud lightning (CL) simultaneously.

Utilizing a high sensitivity, low noise wide-band receiver, state-of-the-art digital filters and equalizers, along with precision GPS time reference, the sensor is able to characterize and categorize the lightning stroke. Once identified, the LPS-200 initiates a TCP/IP message to the Central Analyser Processor (CAPTM) where the precise lightning location is calculated.

The LPS has enormous advantages over other lightning sensor designs, in particular those based on magnetic direction finding (MDF) which suffers from significant site introduced errors and consequent high siting costs. Precision lightning sensors used by GPATS do not monitor magnetic field signals as do Direction Finding (MDF) based sensors, therefore sensors have liberal siting criteria.

The LPS can be installed on existing structures, towers, and buildings where access to electric power and communications is readily at hand. TOA also offers remote site installation utilizing solar power. The LPS is also extremely adaptable in terms of communications; its design allows it to transmit data by telephone, network, internet, or radio as is deemed best suited to the requirement.

Lightning Detector

The detector part of the sensor is a broadband receiver. This picks up a substantial amount of the lightning energy that allows the system to distinguish between ground lightning and cloud lightning. With a broadband detector the different characteristics of ground strokes and cloud strokes can be identified. This allows classification of the detected strokes by the LPS sensors.

In a time-of-arrival based system, timing is an important part of the receiver. The LPS receiver uses commercial GPS timing as a reference. The sensor uses a high frequency timing source that makes the timing more stable, accurate and increases the resolution. The timing is constantly monitored and corrected. This results in more accurate lightning locations.

An on-board processor handles communications and monitors the over-all operation of the sensor. It keeps track of the timing system. The sensor is designed for remote configuration of the hardware. This is accomplished using Field Programmable Gate Array (FPGA) technology. This allows remote configuration of the hardware using bit patterns. Upgrades can be performed without visiting the site.

The sensor is also designed for remote configuration of the software. Software is downloadable over the communications link. The programs are stored in non-volatile memory on the board. It is not affected by power glitches, losses, or outages.

Cloud Lightning Detection

Cloud lightning generates much higher short-term energy at higher frequencies than cloud-ground strokes, which the sensor identifies. The precise timing of a cloud pulse of a certain magnitude will allow the accurate location of that pulse using time-of-arrival mathematics. Due to their very high sensitivity, LPS sensors have no problem detecting cloud stroke signatures; because of the comparatively weaker peak voltages received at the antenna and the effects of propagation delays over longer distances, signal strength thresholds will also be lower than for ground strokes.

Flexible Communications

The sensor supports various communications methods. It has an on-board 10-Base-T network controller that allows TPC/IP communications over a network. There is also a standard serial communication circuit for modem or satellite communications.

Rugged & Reliable Antenna System

The LPS has two antennas; the first is an active GPS antenna used for the timing reference. The second is used for stroke detection and is typically ~ 1 meter in length, with the precise length determined by network performance requirements. Both antennas are small and light weight, have a small wind resistance, and are easily mounted on existing structures without requirements of extensive civil works. They are designed for easy maintenance; and since there are no sensitive electronics mounted outdoors, site selection is simplified and reliability enhanced.

Comprehensive Diagnostic Capabilities

Built-in diagnostics monitor the system and allow remote diagnostics as long as the communications software is running. Sensitivity and other system settings are user adjustable depending upon the needs of system.

Performance Verification

The characteristics of ground lightning are well known and the LPS sensors are programmed to look for these characteristics. The sensors discriminate ground strokes by monitoring the characteristics of the radiated energy at the lower frequencies. The engineers of TOA as well as many other scientists, engineers and operators around the world have measured the detection efficiency and location accuracy of time-of-arrival lightning location systems. To achieve this understanding, one can monitor high towers which receive many lightning strikes. Investigations using three 1000-foot and larger towers located in Florida were performed, allowing for accuracy and consistency to be validated.