Pressure measurement because atmospheric pressure is always changing and the reference in this case is fixed at 1 bar. To produce an absolute pressure sensor, the manufacturer seals a high vacuum behind the sensing diaphragm. If the process-pressure connection of an absolute-pressure transmitter is open to the air, it will read the actual barometric pressure. The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N·m or kg·m·s). This special name for the unit was added in 1971; before that, pressure in SI was expressed in units such as N·m. When indicated, the zero reference is
Comparison of Pascal and Delphi does not go into Delphi-specific extensions to the language, which are numerous and still increasing. 1. The way procedures and functions can be passed as parameters differs: Delphi requires explicit procedural types to be declared where Standard Pascal does not. 2. Delphi does not support so called 'extraprocedural gotos', in which goto statements may reference targets outside the current procedure/function body. 3. Standard Pascal has file 'buffer variables', together with 'get' and 'put' standard procedures that operate on them. Neither are supported in Delphi. 4. Given a variant record in Standard Pascal, the size of a particular variant can be