Cable characteristics for FieldBus

FieldBus, an emerging instrument standard, provides data communication among low-power field instruments. The standard specifies a low-speed data rate, under 100 kb/s using single- and multiple-twisted-pair cables at distances up to 1900 m. The intent is to allow FieldBus instruments to be retrofitted to installed cable currently used with low-frequency, analog-signaling instruments. FieldBus represents a new application for this cable. The cable parameters of importance to data communication, attenuation and phase constants, characteristic impedance, and crosstalk, have been measured in the range of 1 kHz to 100 kHz for a group of 15 representative cables, and the results are presented. A compromise terminator that approximates the cable characteristic impedance in the measured frequency range is proposed.<
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