flex_configure_encoder_filter |
Configure Encoder Filter
Usage
status = flex_configure_encoder_filter(u8 boardID, u8 axisOrEncoder, u16 frequency);
Purpose
Selects the maximum count frequency for an encoder channel by configuring its digital filter.
Parameters
| Name | Type | Description |
|---|---|---|
| boardID | u8 | assigned by Measurement & Automation Explorer (MAX) |
| axisOrEncoder | u8 | axis or encoder to configure |
| frequency | u16 | maximum count frequency selector |
Parameter Discussion
axisOrEncoder is the axis or encoder to configure. Valid values are NIMC_AXIS1 through NIMC_AXIS30 or NIMC_ENCODER1 through NIMC_ENCODER30. On motion controllers that support fewer than thirty axes, configuring non-existent axes or encoders returns error 70006 (NIMC_badResourceIDOrAxisError). For configuring encoders mapped to axes, you can call this function on the axis or directly on its mapped encoder. Refer to Axes and Encoders for axis and encoder resource IDs.
frequency selects the maximum count frequency for the specified encoder.
| frequency Value | Maximum Count Frequency | Max Count Frequency Constant |
|---|---|---|
| 0 | 25.6 MHz | NIMC_ENCODER_FILTER_25_6MHz |
| 1 | 12.8 MHz | NIMC_ENCODER_FILTER_12_8MHz |
| 2 | 6.4 MHz | NIMC_ENCODER_FILTER_6_4MHz |
| 3 | 3.2 MHz | NIMC_ENCODER_FILTER_3_2MHz |
| 4 | 1.6 MHz (default) | NIMC_ENCODER_FILTER_1_6MHz |
| 5 | 800 kHz | NIMC_ENCODER_FILTER_800KHz |
| 6 | 400 kHz | NIMC_ENCODER_FILTER_400KHz |
| 7 | 200 kHz | NIMC_ENCODER_FILTER_200KHz |
| 8 | 100 kHz | NIMC_ENCODER_FILTER_100KHz |
| 9 | 50 kHz | NIMC_ENCODER_FILTER_50KHz |
| 10 | 25 Hz | NIMC_ENCODER_FILTER_25KHz |
Using This Function
Setting the maximum allowable count frequency for an encoder is useful for reducing the effect of noise on the encoder lines. Noise on the encoder lines can be interpreted as extra encoder counts. By setting the frequency to the lowest possible setting required for the motion application, you can ensure the highest degree of accuracy in positioning. In choosing the appropriate value, you must take into account the counts per revolution of the encoder and the maximum velocity for the axis in question.
For example, with a 20,000 counts per revolution encoder and a maximum velocity of 3,000 RPM (50 revolutions per second), the encoder signal could be as high as 1,000,000 counts per second. A frequency value of 4, which would correspond to a maximum count frequency of 1.6 MHz would be appropriate in this case.
If you never call this function, a default value of 4 (1.6 MHz) is used.
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Tip When the encoder filter is changed, reset the position to prevent an erroneous count. |