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To allow the construction of hybrid systems, where the 4–20 mA is generated by the controller, but allows the use of pneumatic valves, a range of current to pressure (I to P) converters are available from manufacturers. These are usually local to the control valve and convert 4–20 mA to 3–15 psi (or 0.2–1.0 bar).
The HART Communication Protocol (Highway Addressable Remote Transducer) is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems.
Older teleprinters used a 60 mA current loop. Later machines, such as the Teletype Model 33, operated on a lower 20 mA current level and most early minicomputers featured a 20 mA current loop interface, with an RS-232 port generally available as a more expensive option. The original IBM PC serial port card had provisions for a 20 mA current ...
A remote terminal unit (RTU) is a microprocessor-controlled electronic device that interfaces objects in the physical world to a distributed control system or SCADA (supervisory control and data acquisition) system by transmitting telemetry data to a master system, and by using messages from the master supervisory system to control connected objects. [1]
An analogue switch: Maxim MAX313. An analogue switch, also called a bilateral switch, is an electronic component that behaves in a similar way to a relay, but has no moving parts. The switching element is normally a pair of MOSFET transistors, one an N-channel device, the other a P-channel device. The device can conduct analog or digital ...
LM3914 driving an LED bargraph display LM3915 IC in DIP-18 package. The LM3914 is an integrated circuit (IC), designed by National Semiconductor in the late 1970s, used to operate displays that visually show the magnitude of an analog signal. [1] It can drive up to 10 LEDs, LCDs, or vacuum fluorescent displays on its outputs. The linear scaling ...
A 20×4-character display. In 8-bit mode, all transfers happen in one cycle of the enable pin (E) with all 8 bits on the data bus and the RS and R/ W pins stable. In 4-bit mode, data are transferred as pairs of 4-bit "nibbles" on the upper data pins, D7–D4, with two enable pulses and the RS and R/ W pins stable. The four most significant bits ...
Analogue electronics (American English: analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term analogue describes the proportional relationship between a signal and a voltage or current that represents the signal.