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Table 7-2. frequency measurement method comparison, Position measurement, Measurements using quadrature encoders – National Instruments Network Device DAQ S User Manual

Page 86: Position measurement -14, Measurements using quadrature encoders -14

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Chapter 7

Counters

NI 6124/6154 User Manual

7-14

ni.com

Table 7-2 summarizes some of the differences in methods of measuring
frequency.

For information about connecting counter signals, refer to the

Default

Counter/Timer Pinouts

section.

Position Measurement

You can use the counters to perform position measurements with
quadrature encoders or two-pulse encoders. You can measure angular
position with X1, X2, and X4 angular encoders. Linear position can be
measured with two-pulse encoders. You can choose to do either a single
point (on-demand) position measurement or a buffered (sample clock)
position measurement. You must arm a counter to begin position
measurements.

Measurements Using Quadrature Encoders

The counters can perform measurements of quadrature encoders that use
X1, X2, or X4 encoding. A quadrature encoder can have up to three
channels—channels A, B, and Z.

X1 Encoding—When channel A leads channel B in a quadrature
cycle, the counter increments. When channel B leads channel A in a
quadrature cycle, the counter decrements. The amount of increments
and decrements per cycle depends on the type of encoding—X1, X2,
or X4.

Table 7-2. Frequency Measurement Method Comparison

Method

Number of

Counters

Used

Number of

Measurements

Returned

Measures High

Frequency

Signals

Accurately

Measures Low

Frequency

Signals

Accurately

1

1

1

Poor

Good

1b

1

Many

Fair

Good

2

1 or 2

1

Good

Poor

3

2

1

Good

Good