12/15/2011 5:01 AM | |
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Hello.... Check this infrormations....my be useful.... Regards, Prakash AttachmentEncoders.pdf (2407 Downloads) |
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12/15/2011 3:32 PM | |
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The selection of the encoder is a combination of cost & accuracy needed for the application. Resolver is magnetic based device measuring device that produces one sine wave per motor revolution. Drive/encoder electronics scan the signal and produce a single motor turn absolute position output. This technology is cheaper then others and fairs better in harsh operating environment (temperature, vibration). Resolvers are usually used to keep costs down in applications where speed or positioning tolerances are not too critical or important. HTL, TTL performance is very similar: the only difference between the two is the type of electronics used and, as a result, different operating voltage. Typical counts of pulse encoders are 2,048 or 4,096, but there are lower and higher count devices available. Unlike other encoder types, the device produces a discrete output pulses on two tracks, A and B, at a single voltage level. A and B tracks are offset by 90 degrees. A combination of two tracks allows control electronics to determine the motor direction and, by counting rising and falling edges of each pulse, to attain a resolution 4x the pulse count. A third channel, Z pulse, is commonly utilized to indicate the zero mark. TTL (5V) electronics can be considered to have better immunity to electronic noise, because each track has two signals, A and A not, which are inverted with respect to each other. By transmitting a differential signal like that allows control electronics to reject the noise that may be present on both signals at the same time. Sin/Cos incremental encoder is an optical scanning device that utilizes a glass disc and a optical scanner to produce 2,048 (typically) sin waves per motor revolution. This is the highest resolution and precision position measuring device.Bacause of the glass disk and plastic gears inside the encoder, it can be more susceptible to vibrations and temperature variations. Although a higher priced device, sin/cos encoder is the preferred measuring device for high precision applications (CNC machines, printing machines, robots, etc) An absolute sin/cos encoder operates the same way as the incremental one, but in addition it has optical tracks and gears to allow the encoder to capture the position across multiple motor revolutions. Attached pdf has a good visual pictures of the basis of operation of each encoder and precision/accuracy specifications. AttachmentEncoder Types.pdf (1518 Downloads) |
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11/6/2014 3:56 PM | |
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