The LPV Transmissometer has been the standard for measuring long-path transmittance for over 20 years.
The Model LPV-3 Long Path Visibility Transmissometer consists of a constant output light source transmitter and a computer controlled photometer receiver. The irradiance from the transmitter at a wavelength of 550nm can be measured to a high degree of accuracy both day and night, and over a path length of up to 20 km. Path length is chosen based on the expected extinction values to be measured. A long path of greater than 3 km is used to measure extinction near Rayleigh and a short path of less than 3 km can be used to measure very hazy or foggy conditions.
Both the receiver and transmitter operate from a 13.8-volt battery source and use 4 and 20 watts of power respectively. The output results can be read as a voltage proportional to extinction or visual range. In addition, a separate serial data interface outputs a string of data items in ASCII format that includes all the calculated extinction values, visual range, raw instrument values and time. The units can operate for long periods of time unattended in a continuous or timed cycle mode. The self-resetting and backup systems ensure continued operation even after power blackouts or computer lockup. Both units can be synchronized, programmed and calibrated at the home station and installed in the field ready for operation.
The Model LPV-3 Transmitter is an upgraded version of the Model LPV-2 Transmitter, which was discontinued in 2003. Instead of two units connected by a cable, the LPV-3 transmitter is contained in one unit with only a low voltage power cable needed. An improved user interface using two buttons with a 4-character display allows for easy control over the expanded LPV-3 features. As of September 2004, the LPV-2 Receiver has been upgraded to the Model LPV-3 Receiver. The large computer control box with thumb switches, rotary switch and analog display has been replaced with a much smaller unit featuring a two-line forty character digital matrix display. All configuration settings are now selectable through a 4-button interface and simple menu system. The LPV-2 Receiver computer controller can be replaced directly with the LPV-3 Receiver controller with no change in cables or operational methods. An improved PC interface allows for complete configuration of the LPV-3 Receiver, testing certain important functions and data capture.
Download and print the Model LPV 3 & LPV-4 Technical Manual for Theory of Operation and Operating Procedures.