Commercial digital audio recorders: a new life for portable Lennartz PCM 5800 seismic stations

Abstract

In the last two decades the use of mobile digital seismic stations has become more and more widespread both for active and passive seismological studies. Many industries have designed and realized seismic stations suitable for portable use and characterized by small dimension and low power consumptions. The modern portable seismic instruments are generally provided with 24 bit AD converter, GPS time code and acquisition on high capacity hard disk and/or continuous data stream for telemetry. These data loggers are generally equipped with high sensibility broad-band seismometers. The PCM 5800 Digital Seismological System has been produced by LENNARTZ ELECTRONIC GmbH (Tubingen, D) since the middle Eighties. It became the first digital seismic equipment for many european and worldwide seismological institutions and laboratories, in many of which it is still in operation. This instrumentation, however, suffers of a weak point which is the acquisition based on a UHER magnetic tape recorder (13cm wheels) with low capacity (about 8 MB; 90 minutes of continuous recording at 4.75 cm/sec speed). This UHER recorder has high maintenance costs and it often needs expensive repairs. We propose to replace the UHER recorders with an easy and cheap solution based on commercial digital recorders with removable media in order to continue to use the high number of instruments (Encoder and Decoder) still held by the seismological community, without any modification to the existing hardware and software.