Mode averaging

[sipower]

Hello again

The data we get back from an accoustic transducer measuring tank levels is quite accurate but has occasional glitches probably caused by external noise. I can implement a mode filter in software on the modbus slave device but its slows everthing down, is it possible within DAQFactory to say take the last 25 readings from a channel and add the value of the reading that occured most to a test channel without resorting to sequences(apart from the Addvalue part).

Your support is really appreciated.

Many thanks

Steve Lawrence

[AzeoTech]

First, you probably should figure out the source of your noise rather than just covering it up. That said....:

Yes. You'll probably want it in the Event on your input channel. Basically you'll use the histogram function:

private histo = histogram(myChannel[0,24], seqAdd(-10,1,20))

The second part of this function defines the bins, in this case the bins go from -10 to +10 in increments of 1. You can do it much finer if you want and of course a different range. Then, you'll need to use a trick to determine which index is the max:

histo = insertTime(histo, -10, 1)

-10 matches the first value in seqAdd(), and 1 the second value. Then you can do:

private maxvalue = getTime(max(histo))

This works because max() will set the time component of its result to the the time stamp of the max data point. We made the time = to the bin, so this gives us the bin. Finally:

maxvalue.time = systime()

myOtherChannel.addValue(maxvalue)

That all said, also consider using the smooth() function. That may clean up your data as well.