Data loggers for geophysical research

Two types of data loggers, developed from generally off shelf components, are described. The loggers use the same recording system, a digital cassette recorder with 4 track, 800 bpi capability. Digital operation with COS-MOS electronics makes for low power, essential in many geophysical studies. The first type of logger is used for long term averages. Pre-amplifiers interface various sensors to low frequency VCO´s which drive ripple counters. The counters are periodically written to tape and cleared for a new count. The unit is flexible in that channels may easily be added, and the sample period, VCO frequencies, and word size are easily adjusted. The second type of recorder produces a burst of data at selected times as is desirable for ocean wave studies. A control system allows one to accurately set start, stop, and sampling times. Both period and cycle counting sampling can be employed depending on the measurement accuracy desired. The units are used in the Coastal Upwelling Experiments and a brief statement of performance is given.