Handheld terminal issues
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This post was last edited by zhoudingshengs on 2023-12-14 09:46. 1. The diagram below shows the wiring diagram for the handheld communicator and the smart transmitter; the handheld communicator is indicated at three locations in the diagram (A, B, and C respectively). Can communication take place at all three of these locations?
Locations A and B can communicate normally, while location C cannot.
Location B can communicate, Location A can usually communicate, while Location C generally cannot communicate. The instrument communication signal is an AC ripple superimposed on a DC current; the handheld terminal receives voltage pulses. A current-to-voltage conversion resistor is required for this purpose, and such a resistor can be one that is connected specifically for this purpose (such as the B terminal), or it can be the output/input impedance of the transmitter/submeter. Normally, the output/input impedance of the transmitter/secondary meter is greater than the required 250Ω (in practice, it is sufficient as long as conversion is possible; the numerical value requirement is not very strict), while the internal resistance of the power supply is less than 250Ω. The switching resistances at different positions are the result of the series and parallel combination of the resistances at each position.
If it’s the HART protocol, I think it should be possible