Digitization of optical lever instruments

Some classical old-fashioned instruments (such as the Wood-Anderson seismometers), as well as some modern instruments (like the all-quartz made Verbaandert-Melchior tiltmeters), conventionally require an impractical recording system obtained by a photographic drum recorder in a darkroom. Simple electronic equipment (made by readily available, low cost electronics) may help in using such kind of instruments allowing a useful digital recording. This will reduce the time-hour in data acquisition and storage (and the manual error), and will increase the accuracy. The theory of operations and some results obtained using the described equipment are shown.