Page 23 - Keubler Motion Sensors

Basics

Encoders Incremental encoders

Multiplication of pulses The resolution of a two channel encoder can be An encoder with physically 5000 pulses per revolu-
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multiplied by two or four using special edge tion can generate 20000 pulses per revolution using
Product overview
detection circuitry. this technique.
Inverted signals When used in environments, with a lot of electrical These signals are always available with output Basics
noise and/or if very long cable distances are re- circuits of the RS422 type and sine wave outputs or
quired, we recommend using encoders with inverted optionally with push-pull outputs.
(complementary) signals.

Resolution The required angular or linear resolution of a given: • Circumference of the measuring
application determines the number of pulses per wheel = 200 mm
revolution. Linear movements must first be convert- • Accuracy of the system = 0.1 mm
ed into rotary, for example by means of a spindle. wanted: • Resolution of the encoder [ppr] 1)
Example:
An encoder is equipped with a measuring wheel. Circumference
Resolution =
Every revolution corresponds to a distance of Accuracy
200 mm (circumference). The accuracy should be
1)
0.1 mm. What is the required resolution (ppr)? The required resolution would be 2000 ppr .

Pulse frequency The required pulse frequency can be calculated as Example:
a result of the number of pulses per revolution (ppr) given: • Speed = 3000 min -1
and the maximum speed (rpm). The maximum pulse • Resolution of the encoder= 1000 ppr 1)
frequency is shown in the data sheet specifications wanted: • Required pulse frequency of the
for each encoder. encoder
Generally this is 300 KHz, but can be up to 800 KHz
with high-resolution encoders. Speed x Resolution
Pulse frequency =
60
The required pulse frequency is thus 50 KHz. This
can now be compared with the maximum possible
pulse frequency of the desired encoder.

This diagram can be used to estimate the required pulse frequency
ppr = 5000 ppr = 2500
350
required pulse frequency [kHz] 300 ppr = 1024

250

200

150

ppr = 512
100

50 ppr = 250

0 2000 4000 6000 8000 10000 12000
–1
speed [min ]

1) ppr = Pulses per revolution
© Fritz Kübler GmbH, subject to errors and changes. 02/2015 www.kuebler.com 21