Absolute encoder signal output are: parallel output, serial output, bus output, integrated transmitter output.
1) parallel output:
Absolute encoder output is the number of digital (or Gray code pure binary code), output parallel interface that is how high and low output point to represent a digital 1 or 0, not high for the median absolute encoder general digital output directly in this form, with direct access to the host computer or PLC I / O interface, the output in time, the connection is simple. But the parallel output with the following questions:
1. must be Gray code, as in the case of pure binary code, there may be a number of changes in the data refresh, reading the wrong code will result in a short time.
2. All interfaces must ensure that the connection is good, because if individual bad connection point that potential is always 0, resulting in the wrong code can not judge.
3. The transmission distance is not far away, usually in one to two meters, the complex environment, preferably with isolation.
4. For more digits, to many-core cable, and to ensure good connection, and the resulting difficulty of the project, the same for the encoder to output at the same time there are many nodes, increase the failure rate of the encoder is damaged.
2) Serial SSI output:
Serial output is by agreement, in time there have data output, this convention is called communication protocol, which is connected physical form has RS232, RS422 (TTL), RS485 and so on. Less serial output cable, transmission distance, the encoder protection and reliability is greatly increased. Usually high number of absolute encoders are used serial output.
3) Fieldbus output
Fieldbus encoder is a plurality of encoders each with a pair of signal lines are connected together by setting the address, the receiving device transmits communication signals, the signal just one interface, you can read a plurality of encoder signals. Bus encoder signals follow RS485 physical format, the presentation of its signal is called communication protocol, currently the world there are multiple communication protocols have their advantages, yet unified, encoder communication protocol commonly used in the following categories: PROFIBUS -DP; CAN; DeviceNet; Interbus like.
Bus encoder can save cable, the receiving device interface, transmission distance, but also can greatly reduce costs in the case of multiple encoders centralized control.
4) integrated transmitter output
For some manufacturers of absolute encoders, which has been in the encoder signal transmitter output directly after conversion, it has an analog 4-20mA output, RS485 digital output, 14-bit parallel output.
7, the signal connection
1. Connect the PLC or PC
2. Connect the dedicated display switching instruments
1) If the parallel encoder output can be directly connected to PLC or PC input output contact I / O, its mathematical signal format should be a Gray code. Encoder How many will take up the PLC how many contacts, if it is a 24 volt push-pull output, active high 1, a low level of 0; if it is an open-collector NPN output, the connection contacts must It is NPN type, the active-low, low level of 1.
2) If the encoder is a serial output, due to limitations of the communication protocol, followed by electrical equipment must have a corresponding interface.
3) the encoder output bus case, the receiving device to be equipped with a dedicated bus modules, such as PROFIBUS-DP.
However, if the bus select output of the encoder, in the middle of the encoder and the receiving device PLC, you can not add other display devices, for live shows, the signal will be transferred out of the match to give the signal indicator from the PLC.
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