Microprocessor-based system for collection and storage of the equine vectorcardiogram

To evaluate the clinical application of a semiorthogonal lead system for use in the horse, an inexpensive means of recording and storing the ECG was required which would allow the subsequent vectorcardiographic analysis to be computerized. In investigating the various options for the system the basic requirements for the digitization of analogue data were reviewed and previous studies examined. The system subsequently developed used an 8080 microprocessor and a multichannel 8-bit analogue to digital converter. This unit was signal-level compatible with the laboratory recorder used in the study and was capable of functioning as a remote terminal. Storage was achieved through the use of a dual-drive task storage system. Programs were written in machine language, both to control the data acquisition procedure and subsequent storage and to facilitate the transfer of data from the microprocessor to a central computing facility for analysis. Data were collected with 8-bit accuracy at a sampling rate of 2,702 samples/s/ channel for 3 channels of data with a system frequency response before digitization of 0.05 to 2,500 Hz. Preliminary analysis indicated that for accurate reproduction, the frequency response of the system before digitization should be a minimum of direct current, to 1,300 Hz, dictating a sampling rate of at least 2,000 samples/s.