For example, to measure pressure, an air or oil hose runs 3 or 4 metres from the engine to a pressure transducer. The transducer has a diaphragm that converts the pressure into an electrical signal we can measure. Temperatures are often measured with K-type thermocouples. These are robust and cheap, and sufficiently accurate for the task. For a discussion of thermocouples see Issue 5 of Monitor .
Speed is measured in revolutions per minute by a tachometer.
This produces either a voltage output, or a pulse output. You need a counter interface module to handle the pulse output. You wire the transducers to the data acquisition interface. This is often remote from the computer and connected to it over an RS485 cable. It also lets you distribute several data acquisition devices around the site, connecting them all to one cable and computer.