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Filter Issue

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Filter Issue

Posted: Tue Jan 30, 2007 7:20 pm

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I have an array of 5 sensors. I am trying to filter it while I get it from the ADC. As in I am trying to make sure that the new value is not greater than the old value by more than10 %. I need to have the final array as an array of 16bit values.

Here is what I tried:

New Value = ((1-0.10)*(Old Value)) + (0.10*(New Value))

Here is what I did in the code:

Code:

int16 Sensor1[5];
int16 Sensor2[5];
double e =0.10;
int i;

I update all the values in Sensor2[5] by reading the 5 sensors with the ADC.

Then I do the following:

Code:

i=0;
for(i=0;i<5;i++) // Initialize Sensor1 Array.
{
Sensor1[i]=0;
}

for(;;)
{

//I update all the values in SensorOld[5] by reading the 5 sensors with the ADC.

i=0;
for(i=0;i<5;i++)
{
Sensor1[i]=((1-e)*(Sensor1[i]))+(e*(Sensor2[i]));
}

}

I would appreciate it if someone could find whats wrong with this code!

Thank you.

kender

Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley

Re: Filter Issue

Posted: Tue Jan 30, 2007 8:11 pm

Reply with quote

Anonymous wrote:

... As in I am trying to make sure that the new value is not greater than the old value by more than 10%. ...

Here is what I tried:

New Value = ((1-0.10)*(Old Value)) + (0.10*(New Value))

You formula alone (which, I think, is an FIR filter) doesn't guarantee that the new value will be within 10% of the old value. Imagine a case, when the new value is more than 10 times bigger than the old value.

Anonymous wrote:

I would appreciate it if someone could find whats wrong with this code!

What's wrong with the output that the present code produces?

Neutone

Joined: 08 Sep 2003
Posts: 839
Location: Houston

Re: Filter Issue

Posted: Wed Jan 31, 2007 10:48 am

Reply with quote

Anonymous wrote:

I have an array of 5 sensors. I am trying to filter it while I get it from the ADC. As in I am trying to make sure that the new value is not greater than the old value by more than10 %. I need to have the final array as an array of 16bit values.

Here is what I tried:

New Value = ((1-0.10)*(Old Value)) + (0.10*(New Value))

Here is what I did in the code:

Code:

int16 Sensor1[5];
int16 Sensor2[5];
double e =0.10;
int i;

I update all the values in Sensor2[5] by reading the 5 sensors with the ADC.

Then I do the following:

Code:

i=0;
for(i=0;i<5;i++) // Initialize Sensor1 Array.
{
Sensor1[i]=0;
}

for(;;)
{

//I update all the values in SensorOld[5] by reading the 5 sensors with the ADC.

i=0;
for(i=0;i<5;i++)
{
Sensor1[i]=((1-e)*(Sensor1[i]))+(e*(Sensor2[i]));
}

}

I would appreciate it if someone could find whats wrong with this code!

Thank you.

That code looks like it was written to run on a PC with the extensive use of floating point and use of ambiguous variable types. It's faster to just filter by a binary fraction such as 1/8 or 1/16 and do all the math in Int16.

http://www.ccsinfo.com/forum/viewtopic.php?t=19509

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