The Measurement Station Of Electrical Parameters

This text introduces a design of the measurement station of electrical power parameters. The system adopts three kinds of technologies: electric measurement technology, FB technology, and communication technology. It realizes quick, accurate and real-time measure. The whole system is composed of mainframe, concentrators and acquisition units. Acquisition unit samples real-time electric power parameters and has RS-485 communication interface. So concentrator can sample data from acquisition unit and transmit command to acquisition unit. Concentrator can transmit data from acquisition unit to mainframe to realize assaying and transacting real-time measurement messages.Acquisition unit also can be named as intellectualized sensor. Electric parameters can be acquired by it. This text adopts a sampling method based on frequency multiplication phase-locked to detect harmonics and can avoid spectrum leakage. It can reach high precision and can anti-alias by taking FAFT algorithm to analysis sampling.RS-485 bus adopts principal and subordinate mode to communicate. Concentrator is a Host. Acquisition unit is a subordinate. It can't send forwardly out orders or datum. Everything is controlled by the host. And subordinates can't communicate each other. In course of RS-485 circuit design, I choose SN65LBC184. This chip has the immunity to instantaneous noises coupling on the data bus. Thereby the dependability of data communication has material improvement.CAN is a kind of serial communication bus whose working is multi-host. Any node of the network can momentarily and forwardly send message to other nodes. So the mode of communication is more flexible. Each concentrator is a unattached CAN-bus node. And each node is composed of CAN controller, CAN-bus transceiver and photoelectric coupling isolation circuit.This text also introduces the main point of the design on CAN-bus node in detail. Some weak points and the aspects of needing improvements are brought forward.