Why 4 20ma standard

The voltage from the sensor is sent to the transmitter to convert in a standard form of the current output signal. Live Zero i. It is easy to detect that the signal wire is not broken. If the range zero were truly zero mA, then there would be no current, and therefore no power to drive the field instrument.

Field instrument would require 3 or 4 wire devices. Additional wiring costs come into account. Another reason for choosing 4 mA is when the transmitter was first introduced, it was working on pneumatic pressure signal for transmission. Later, electronics chips were introduced those require a minimum of 3 mA of current to function.

Different type of standard signals are used in Industrial Instrumentation. The measuring device has ohm resistor. As for current signals,they are converted to voltage signals like this. If instrument is faulty,it can be easily identified. More Articles. Instrumentation Design.

Why mA Standard is so popular? Send this to a friend. Send Cancel. Furthermore, using multiple loops can lead to ground loops problems if the individual loops are not isolated. One other advantage of mA current loops is safety. Also, the mA current loop is intrinsically safe for hazardous areas that may include dangerous levels of dust or vapor because the low power consumption does not cause combustion if normal operating or fault conditions are in play.

Of course, if the use of wireless sensors continues to grow, the mA input loop distance of 1, meters will not be as impressive as it was in the s.