Delta CS24D User Manual download pdf (Page 26)

8.5 Averaging and Response Time

Since the internal signals used by CS24D can be fairly weak (especially with dark target colors), they

are subject to a variety of electrical and optical noise sources. The CS24D uses an exponential moving

averaging allowing up to 4096 readings to be averaged to reduce noise. In many applications,

averaging provides significant performance improvements, and we generally recommend setting the

averaging as high as is practical. The limiting factor is the response time.

The chart below shows the CS24D response time for various conditions:

Sort Outputs

Used

Averaging

Output Update*

Response Time

Minimum

Response Time

Maximum*

1 to 4

2ms

3ms

1 to 4

Yes

2ms

Readings Averaged

+ 4ms

(Readings Averaged x2)

+ 2ms

5 to 8

3ms

4ms

5 to 8

Yes

3ms

Readings Averaged

+ 4ms

(Readings Averaged x2)

+ 4ms

9 to 16

4ms

6ms

9 to 16

Yes

4ms

Readings Averaged

+ 4ms

(Readings Averaged x2)

+ 4ms

*Serial communications over the RS232 port can add up to 7ms to the Update and response times

depending on data transfer activity. The CS24D color sensor is not intended to be operated with the

RS232 Serial port in use.

The CS24D reads all four LED colors once per millisecond. The output update time depends on the

setup, in particular the number of Sort Outputs used and the number of readings averaged. Readings

are averaged using a sliding window number of milliseconds worth of readings. Each millisecond a

new reading is added to the window and the oldest reading is removed. The outputs are continuously

updated at the Output Update rate.

The total response time, from when an object is placed under the sensor to the time the outputs are

updated to reflect the color of the object, is dominated by the Averaging parameter for settings of 4 or

above. The exponential moving average takes 1 to 2 milliseconds per reading averaged to reach the

new reading, depending on the difference between the readings.

Note that during the time that the sensor is averaging the data from a new object, the outputs may

temporarily show an incorrect value based on the average of the new color and the previous color. To

prevent this, the host system should delay for a period of time at least equal to the Maximum Response

time before using the CS24D outputs after a new object is placed in the sensing area.

An additional parameter that can affect response time is the Pulse Stretch parameter. This parameter

causes the CS24D to make sure that any binary Output is maintained for at least the number of

milliseconds specified by the Pulse Stretch parameter. For maximum response, set the Pulse Stretch

parameter to 0.

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Delta CS24D User Manual Page 26

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