Design allows for a direct electrical connection to shutter
Large electric fields associated with the hazardous separation of charge occur during thunderstorms. Therefore, knowledge of the atmospheric electric field at ground level is useful for thunderstorm research and lightning warning. The graph above depicts the chronology of a local thunderstorm from the onset of hazardous electrification, to lightning discharges, to returning to fair weather conditions. There is not a universally accepted lightning warning criteria that is based on electric field measurements. However, the graph demonstrates that the local electric field provides critical warning information, especially for developing thunderstorms.
The traditional instrument for measuring the atmospheric electric field at ground level is the rotating-vane field mill, so named because a rotating vane "chops up" or modulates the electric field seen by sensing electrodes. Field mills employ a continuously rotating vane that is electrically connected to earth ground through a rotating electrical contact.
In contrast, the CS110 uses a stepper motor to open and close a reciprocating shutter to alternately shield and expose a sensing electrode from external electric fields. The reciprocating approach allows for a direct electrical connection to the shutter instead of a problematic rotating contact. The fully closed shutter position on the CS110 also provides a zero-field reference for each measurement cycle, allowing for DC error correction. Additionally, deenergizing the stepper-motor coils between shutter movements results in reduced power consumption and measurement noise.
The CS110 includes an embedded datalogger to control the reciprocating shutter and measure the output voltage from a charge amplifier. A versatile programming language, CRBasic, provides flexibility in choosing measurement rates, onboard data processing, digital control, and alarm thresholds. Along with electric field, the CS110 system can measure wind speed, wind direction, air temperature, relative humidity, solar radiation or barometric pressure, and rainfall with the addition of external sensors. LoggerNet Datalogger Support Software provides comprehensive monitoring, data collection, and networking capability for the CS110.