Over two years of 1-minute accumulations from each of three wires in a Geonor gauge installed in a pit located on the north campus of the University of Oklahoma, Norman (not part of the USCRN) have been analyzed to answer the following questions: (1) what is the sensitivity of the output of a vibrating-wire to temperature on the time scale of a daily cycle? (2) is this temperature sensitivity related to bucket accumulation and/or mean daily temperature and, if so, how? (3) what is the effect of wind speed on the resonant frequency of a vibrating wire? (4) with regard to estimating accumulation, is there any advantage in using the method that counts the number of cycles over a fixed time interval compared to the method that measures the time for a fixed number of cycles to occur (instructions P3 and P27, respectively, in the CSI data logger)? (5) what is the lowest 1-minute rain rate that can be measured before system noise overwhelms the signal?
The results of the analysis show that the temperature sensitivity is negative and its magnitude depends on a particular vibrating-wire and accumulation in the bucket. Further results show that the noise in the output generated by wind speed is in proportion to the speed and, for determining 1-minute rain rates, it is advantageous to measure the time for a fixed number of cycles to occur (instruction P27). Examples of 1-minute rain rates in light drizzle will be shown.