Appendix A Glossary

Page A.1

Appendix A Glossary A
ADC See Analogue to digital converter
Address A number which uniquely identifies a location.
Alarm An indicator which shows when a failure has occurred. Alarms are
classified as System, Input or Limit.
API American Petroleum Institute
Analogue input An input where information is received in analogue form.
Analogue output An output from which information is transmitted in analogue form.
Analogue to digital converter A circuit that converts analogue voltages or currents into digital (usually
binary) numbers which can then be processed by computers. The
digital signal gives the amplitude of the analogue signal at a particular
instant. See also Digital to analogue converter.
AUI Short for AttachmentUnit Interface, the porti on of the Ethernet standard
that specifies how a cable is to be connected to a transceiver that plugs
into a 15-pin socket
B
Bar A unit of pressure. 1 bar = 105 Nm2.
Base condition Base or Standard Conditions give the volume which would have been
transferred if the temperature were at a pre-defined figure. The actual
values for base temperature and pressure vary from country to country.
Base density Density of a fluid measured under base conditions.
British Thermal Unit The energy required to raise the temperature of one pound of water
through one degree Fahrenheit.
BTU See British Thermal Unit.
C
Calibrate To assess the performance of an item of equipment against that of
another one whose accuracy is known.