The details of the present experiment have earlier been described by Pant & Sagar (1998). For recording the microthermal fluctuations at a level, pair of thermal sensors made of thin (25 in diameter) Nickel wire is used. The horizontal separation between the two sensors is one metre. They are mounted at heights of 6, 12 and 18 m above the ground on the mast. Thus, the inter-spacing between the microthermal sensors is m. The length of a sensor-wire is chosen in such a way that its effective resistance comes out to be ohm at room temperature. This yields a temperature resolution of C for the system. For recording the instantaneous ambient temperature around the microthermal sensors with an accuracy of C, Pt-100 RTD temperature sensor and ADAM-4013 analog input module are used. Analog input module ADAM-4013 uses a microprocessor controlled integrating A/D converter to convert RTD signals into digital format. The data are recorded in a PC with the help of the ADAM series of analog input modules and immediately processed in the PC. The ADAM series is a set of intelligent sensor-to-computer interface modules, containing built in micro-controller yielding 16-bit resolution in A/D conversion. They are remotely controlled. The commands are transmitted in RS-485 protocol. The signals from the sensors and RTDs are connected to the electronic circuit inside the observing room by cables. A DC current is fed through these sensors whose resistance changes according to microthermal fluctuations and consequently, produces variable voltage signal for differential amplifier. The amplifier output is sent to a signal processing equipment. The GENIE software package was used for data acquisition, processing and control. Atmospheric pressure is almost the same within a height of 18 m. Its observed value at Devasthal is mb which has been used in our further data analysis.
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