Home

Previous

Up

Next

MultiCam Boards Documentation > MultiCam Documentation > MultiCam User Guide > The Channel Class > Understanding the Rate Converter > Programming the Rate Converter > Setting the Rate Conversion Ratio in the MultiCam Environment

Setting the Rate Conversion Ratio in the MultiCam Environment

MultiCam proposes two integer parameters to program the rate conversion ratio, namely LinePitch and EncoderPitch

LinePitch declares the distance between two successively scanned lines on the moving web. The LinePitch parameter must be expressed in the same length unit used with EncoderPitch.

EncoderPitch declares the distance traveled by the web between two successive pulses provided by the encoder.

We recall the formula to evaluate the web axial pitch for a desired aspect ratio:

The two pitches should be scaled to some integer values in such a way the ratio is as accurate as possible. Those MultiCam parameters should have an integer contents in the range 1 to 10000.

To make this clear, consider the representative example.

The encoder pitch is 0.75 mm, as imposed by the mechanics.

The web axial pitch for a unitary aspect ratio is 0.391 mm.

Enter the figures in an arbitrary unit that will bring the pitches to an integer value while maintaining their ratio.

In this case, correct settings are:

LinePitch=391

EncoderPitch=750

This is equivalent to entering the pitches in micrometers.

The rate conversion ratio will be programmed to:

In the representative application, RateConversionRatio = 1.918

This procedure is merely a means to enter a programmable ratio into the MultiCam system with an accuracy in the order of magnitude of 1/1000.