Final answer:
0-10 VDC, 4-20 mA, and 3-15 psi are examples of analog signals commonly used in instrumentation and process control. These signals convey continuous information from sensors to control systems and are standardized for compatibility and ease of use in various applications.
Step-by-step explanation:
The signals 0-10 VDC, 4-20 mA, and 3-15 psi are examples of standardized analog signals used in process control and instrumentation. These signals are used in various industries for transmitting information from field sensors and transducers to control systems or display panels. Devices like pressure gauges result in a direct physical force which is then transduced, or converted, into an electrical signal. This electrical signal can be in the form of a voltage or current and is often used because it can be easily manipulated, transmitted over long distances, and interfaced with electronic equipment.
For example, in a 4-20 mA current loop, the current is directly proportional to the physical quantity it represents. If the pressure, for instance, falls between 3-15 psi, the transmitter might be set up such that 3 psi corresponds to 4 mA (the loop's minimum current signal), and 15 psi corresponds to 20 mA (the maximum signal). As analog signals, these represent continuous values rather than discrete steps, unlike digital signals which have been encoded into a binary form with specified voltage cut-off values for recording or computation in digital devices.