High Speed Digital Data Inputs for Thermal Array Chart Recorders

Abstract

Many telemetry stations would like to convert from using digital-to analog converters (DAC's) to using direct digital inputs to their chart recorders but can't find a suitable recorder interface. These stations often have hundreds or even thousands of channels of information being bussed around at very high speeds on propriatary real-time computer systems. The lack of standardization has naturally presented recorder manufacturers with problems in selecting the appropriate interface hardware. Standard parallel interfaces, such as SCSI and GPIB, are usually too slow and not really suited for real-time transfer, although they can be used in some circumstances which will be described. The best choice seems to be a general purpose parallel port of at least 16 data bits which can support a large number of addresses. Such an interface can be used with a high speed network like SCRAMNet as well as with a general purpose computer or workstation. This paper will describe several available parallel ports using both TTL and RS-485 (long-line) hardware and some practical implementations of thermal array recorder use with SCRAMNet, GPIB, and general purpose parallel busses.