How does the 4-20 mA Receiver works?

The sensor is an input device that provides a suitable output to respond to the input measure. The sensor is also called the primary sensor, sensor or initial detector. The measure is the physical benchmark to measure.

The Input Power Adapter produces an electric output to measure the input. Its product is conditioned and ready to be used by receiving electronic devices such as plc or dcs.

Receiving Electronics can serve as an indicator, console, computer, PLC, DCS ETC. The term “sender”, as is commonly used with industrial process controls, has a more narrow definition of sensors or Power Adapter:

4-20 mA transmission

The transmission is a power adapter that responds to the size of a sensor and turn it into a standard transmission signal (such as 4-20 ma) and is a function only for the size size.

The Radios can contain any of the multiple electrical delivery plans. The most common and easy to use is the dual-wire connection. This is generally the basic basis for industrial process control systems when digital communication is not required. As shown in the figure below, two baskets are used only to accommodate both the power of the sender and the output reference from the sending.

To facilitate the closed loop control system, you need to get information from the process before the control unit can determine which action the control might require. Some common names of sensors that provide information are sensors, energy adapters and / or radios.

The current standard ring is usually from 4 to 20 mah. Important calibration teachers with current ring are zero, full range, and range. With a range of 4 to 20 mah, the ring current is usually 4 Mah when the measurement or process variable is at zero level, and 20 mah when the measurement or process variable is wide. The difference between zero and full size, 16 mah, extension. Thus, the range is compatible with the specific range of measure or process variable.

When considering the flow receiver, for example, the measuring range or process variable range from 0.0 to 100.0 M3 / H, equivalent to a loop current from 4 to 20 Mah (the output period extends to 16 mah; the output reduction factor is 0.16 Mah / (M3 / HR 16 ma).

4-20 ma working transmission
Assumption: Standard + 24 v DC with 20 ma

In the year PLC / DCS provides more than 20 ma current to run the ring.

Status 1: Operation Variable @ 0 %
PLC / DCS Analog Input Card + 24 v continuous current and 20 mah to operate the receiver.

One Pair Cable is used to operate the receiver and uses the same cable to receive data in the current 4-20 ma range.

The Sender + 24 v DC, receives more than 20 ma signal in the ring. Minimum + 5 V DC, 20 ma signal is required for good operation in transmission. In Practical application there will be reduced effort in the ring.

The sender has the function of an effort organizer which is used to organize a current ring. The transmission will be formed with lrv, urv and other process variable details. The ring stream will be changed / changed by the sender according to the process change.

4-20 ma current will be transformed into a 1-5 v DC standard using 250 Ohm Precision Resistance. The Analog to digital adapter will be used to convert the effort into a digital signal which is used to indicate the practical variable value in the DCS / PLC HMI.

4-20 mA Receiver works

Example: a transmission flow with a set of 0 to 100 M3 / h. The sender indicates 0 M3 / hr for no flow in the line. DCS / PLC power transmission with + 24 v DC, 20 ma. Since process extensions is 0 M3 / hr, the receiver organizes the ring stream to 4 ma and effort.