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Glossary
890USE19600 April 2004 65
RTD resistive temperature detect. An RTD device is a temperature transducer composed
of conductive wire elements typically made of platinum, nickel, copper, or nickel-
iron. An RTD device provides a variable resistance across a specified temperature
range.
Rx reception. For example, in a CAN-based network, a PDO is described as an RxPDO
of the device that receives it.
SAP service access point. The point at which the services of one communications layer,
as defined by the ISO OSI reference model, is made available to the next layer.
SCADA supervisory control and data acquisition. Typically accomplished in industrial
settings by means of microcomputers.
SDO service data object. In CAN-based networks, SDO messages are used by the
fieldbus master to access (read/write) the object directories of network nodes.
segment A group of interconnected I/O and power modules on an island bus. An island must
have at least one segment and, depending on the type of NIM used, may have as
many as seven segments. The first (leftmost) module in a segment needs to provide
logic power and island bus communications to the I/O modules on its right. In the
primary or basic segment, that function is filled by a NIM. In an extension segment,
that function is filled by an STB XBE 1200 BOS module. (An island running with a
basic NIM does not support extension segments.)
SELV safety extra low voltage. A secondary circuit designed and protected so that the
voltage between any two accessible parts (or between one accessible part and the
PE terminal for Class 1 equipment) does not exceed a specified value under normal
conditions or under single-fault conditions.
SIM subscriber identification module. Originally intended for authenticating users of
mobile communications, SIMs now have multiple applications. In Advantys STB,
configuration data created or modified with the Advantys configuration software can
be stored on a SIM and then written to the NIM’s Flash memory.
single-ended
inputs
An analog input design technique whereby a wire from each signal source is
connected to the data acquisition interface, and the difference between the signal
and ground is measured. Two conditions are imperative to the success of this design
technique—the signal source must be grounded, and the signal ground and data
acquisition interface ground (the PDM lead) must have the same potential.
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