Design of a simple low cost tethersonde data acquisition system for meteorological measurements

Abstract

A tethersonde instrument for vertical sounding in the lowest height region of the atmosphere designed using commercially available solid state sensors is presented. This instrumentation which was developed for high-resolution measurements of the vertical profiles of atmospheric temperature, humidity, and pressure to study the evolution of radiation fog in winter over Delhi, measures the pressure (800–1100milli-bar), temperature (0–35°C), and relative humidity (0–100% RH) and includes an eight-channel 12bit data acquisition unit and a low-power digital, FM telemetry system operating at 173MHz and uses a PC printer port connection for real-time data logging and operates from a single 9V supply. It is capable of providing data to high resolutions of better than 0.01°C for temperature, 0.07mb for pressure, 0.1% for the relative humidity, and the system has a response time of ∼50s. The sonde can accommodate up to six different sensors according to sounding requirements. The data are serially streamed into the PC and the identification of data from the different sensors is accomplished by using a sync word which is included as a part of the data stream. The sonde has been flown quite successfully a number of times and the flights made thus far have shown excellent performance. The design implementation facilitates easy recalibrations of the individual sensors and their replacement upon failure.