Cognex MVS-8000 Series, Руководство по оборудованию

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3 Using Encoders with Line Scan Cameras
MVS-8600 Hardware Manual 83
200mV range with some small margin). Putting all this information together it is then
possible to calculate the resistor value required to provide the correct signal voltage
with minimum current draw.
For the scenario of a 0 V to +12 V differential voltage signal pair (V+ minus V- = +12 V),
the resistor value is determined as shown.
Refer to Table 28 below for the various recommended resistor values, depending on the
encoder’s signal. It is important to note that, if necessary, line voltage regulators such
as a passive decoupling capacitor can be added to the circuitry to bring the common
mode voltage into the acceptable range, as given by the absolute range requirement of
0 V to +5 V (referenced to ground).
Table 28. Recommended series resistor values
Connecting Encoders
If your application will use encoder-triggered image acquisition, then you must set up
your Cognex software package to be aware of the characteristics of your encoder
hardware. Your encoder vendor’s documentation provides your encoder’s basic
characteristics, such as the number of encoder cycles per revolution. Your Cognex
software package’s documentation includes formulas and examples for translating the
encoder’s cycles per revolution into the number of encoder steps for each line of image
acquired by the line scan camera.
 
  



 
2300
5
5 . 11
100
5 . 0
5 . 0 12
1
mA
V
V
V V
R
R I V
Encoder Output Absolute Voltage Range
Interface option 0 V … +5 V 0 V … +12 V 0 V ... +28 V(max)
Series resistors (R
1
, R
2
) None needed
2.3k

(kOhms) 5.5k

(kOhms)