The encoder application in gravity meter

Into a electrical signal; Rotary photoelectric encoder is divided into two kinds, absolute encoder and incremental encoder.

Incremental encoder pulse output of the sensor, the encoder is much simpler than absolute encoder encoder and higher resolution. Typically require

To three bar code, the code has in fact do not have absolute encoder code word meaning, but the count pulse is produced. The encoder heretics

And the way you have the same number of evenly distributed among transmission and opaque sector (grating), but the two sectors on staggered half of the area. When the code

Disc rotates, the output signal is the phase difference of 90 ° of the A and B phase pulse signals, and there is only one way of pervious to light 3 yards of the slit

Pulse signal (as the benchmark position encoder, for counting system to provide an initial zero signal). From A, B two output signal

Phase relationship (lead or lag) can determine the direction of rotation. When the encoder is turned, A channel pulse waveform than the road ahead of PI / 2 B, and reverse,

A channel pulse than B lagging of PI / 2. A practical circuit, with A plastic wave of down along the trigger is produced by the monostable pulse and B plastic wave phase '

And, when the encoder is to turn only positive pulse output, on the other hand, only in reverse pulse output. Therefore, the incremental encoder is according to the output

Pulse source and pulse count to determine the rotation direction of the encoder and the relative angular displacement. Usually, if the encoder is N (code word) output signal, its

Phase difference of PI/N, can count pulse is 2 N times the number of grating, N = 2 now. Circuit fault is sometimes error, mistake pulse generated it

Case occurs when a signal in a 'high' or 'low' level, and the other a signal is in between "high" and "low"

To change state, the encoder while not produce displacement, but single direction of the output pulse is produced. For example, code disc is shaking or manually

Alignment position (you can see below, will have this kind of situation when gravimeter measurements).

Is a can not only prevent pulse but also improve the frequency resolution is four times the subdivision circuit. Here, the memory function and type D flip-flop

The clock generating circuit. Each have two concatenated D flip-flop, in this way, at the interval of the clock pulse, the two Q end (such as 74 ls175 corresponding B way

2, 7 pins) to keep the first two clock period input status, if both are the same, say the clock interval that no change; Otherwise, you can root

According to the relationship between tell it to changes in the party, resulting in a 'forward' or 'reverse' output pulse. When a certain way due to vibration in the 'high',

'low' reciprocation between change, will have a "positive" and "reverse" alternating pulse, it replaces on two counter number and when you can eliminate it

The influence of the (instrument readings will also be involved in this below). Thus, the frequency of the clock generator should be greater than the greatest possibility of vibration frequency

Value. By figure 4 can also see that in the original a pulse signal cycle, four count pulse are obtained. For example, each lap pulse count to 1000

The encoder can produce four times the frequency of pulse number is 4000, the resolution is 0.09 °. In fact, at present this kind of sensor products are photosensitive yuan

An output signal amplification circuit and sensor detecting element such as plastic packaging together, so just add segmentation and counting circuit of a

An angular displacement measurement system (74159-16 4 decoder).