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Control valve with pneumatic diaphragm actuator and "smart" 4–20 mA positioner which will also feed back the actual valve position and status over the current loop. The 4–20 mA convention was born in the 1950s out of the earlier highly successful 3–15 psi pneumatic control signal standard, when electronics became cheap and reliable enough ...
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 ...
Closed-loop regulator circuits using the TL431 are always designed to operate in high transconductance mode, with I CA no less than 1 mA (point D on the current-voltage curve). [8] [7] [2] For better control loop stability, optimal I CA should be set at around 5 mA, although this may compromise overall efficiency. [30] [7]
In the 1950s, when high gain electronic amplifiers became cheap and reliable, electronic PID controllers became popular, and the pneumatic standard was emulated by 10-50 mA and 4–20 mA current loop signals (the latter became the industry standard). Pneumatic field actuators are still widely used because of the advantages of pneumatic energy ...
Different test standards apply for consumer electronics, military electrical devices, high-voltage cables, switchgear and other apparatus. [2] Typical hipot equipment leakage current trip limit settings range between 0.1 and 20 mA [3] and are set by the user according to test object characteristics and rate of voltage application. The objective ...
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