The transmitter is the heart of the 4-20mA signalling system. It changes a physical property such as temperature, humidity, or pressure into an electrical signal. The signal is a current proportional ...

Although several ranges are used, the most popular is still the 4- to 20-mA standard. Loop accuracy depends on the transmitter’s ability to transform the sensor signal to a current.

It’s based on pulse-width modulation to implement a cheap but accurate current-loop transmitter. A dual-channel isolator (E1-E2-Q1-Q2) provides galvanic isolation of the PWM input.

Specific applications for true RMS current transmitters include monitoring VFD controlled loads and accurately measuring phase angle- or burst-fired, time-proportioned SCR controlled loads.

To eliminate errors introduced by possible spurious current paths, the signal must be DC-coupled with full galvanic isolation, yet inserted with accuracy. The circuit of Figure 1 comprises a ...

Current high-speed transmitters and receivers in telecommunication are dependent on power-hungry digital signal processing according to Payam Heydari, senior author and professor of electrical ...