On Tue, 3 Feb 1998, Lawrence Lile wrote:

> > I have a meter to measure the fuel level of a tank 0=empty 255=full.
> > I want to use software to provide a buffer so that the slosh of the
> > fuel is not seen on the fuel gauge.
PTM: Q&D solution:
TEMP = (TEMP + NW)/2
This needs 8 bit + carry to handle 0..255 values.
This function works if the sloshing makes small differences to both sides
of the right one and the time period is rather short, about 1/20 sek.

If this still give odd values, you can make even:
TEMP = (TEMP + NV - TEMP/D)
VAL =TEMP / D
There   TEMP is a 16 bit register for the summ
        NV = nev measured value (0..255)
        D is 2,4,8,16... (2^n) static
        VAL is the value that is shown in the display.
This gives you totally wrong values from the first D*5 times (I tried
this) but after that you get every time a bit better approximation.
D is selected as a 2^n to get the program easier.

You can even make a try with QBasic:

'--------------------------------------------------
'PTMUSTA@UTU.FI
'Demonstrating running averages
'shareware ;)
'--------------------------------------------------
CLS
NV = 3
D = 4
FOR i = 1 TO D * 6
    'here we simulate random slosh
    NVU = NV + (RND(1) - .5) / 10
    'running average value
    TEMP = (TEMP + NVU - TEMP / D)
    DISPLAY = TEMP / D
    PRINT i;"New=";NVU;"Displ=";DISPLAY;"err=";(DISPLAY-NV)/NV;"%"
NEXT



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PTM, pasi.mustalahti@utu.fi, ptmusta@utu.fi, http://www.utu.fi/~ptmusta
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Lab.engineer (PC support) Computer Center                       OI7234
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