Implemented in the industrial process monitoring and control using a variety of automated instruments, control systems and actuators, the weak Millivolt signal transmission between them, MA-class small-signal
multipoint earthing form a "ground loop" effect
System connection of grounding for various reasons, this device signals between electrical potential difference may exist between reference points, to form a "ground loop" causing distortion in the signal transmission
To solve the "ground loops" signal distortion, according to the analysis of theory and practice, there are three ways: a
First: all the devices are not grounded, this loop has only one point, unable to form a loop, this approach may seem simple, but in practice, it is difficult to achieve, because some devices must be grounded in order to guarantee the measuring accuracy or ensure the security of the person, there are some devices may corrode because of the long and wear or climate impact caused by insulation down to form a new grounding point.
Second: try to make two locations have the same potential, but because of the grounding resistance of geological conditions and the influence of many factors such as climate change, which in fact are not fully able to do in practice.
Third: the methods used in the process loop signal isolation, disconnected process loops, while not affecting the normal transmission of signals, thus thoroughly solving ground loop problems
signal power conflict
Some receive the signal input terminal of the device with a 24V power supply (loop powered input), and field for four-wire transmitter output signal is active and the signal. At this time, such as signal directly to the receiving device, four-wire system transmitter signal with two-wire power signal from the receiving device will conflict solving the problem would require the use of isolators, current input, you can use similar (dual-channel) isolator; for voltage input, you can use similar (single channel)