Math channel formulas

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volrem
TwoWaves
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Joined: Fri Jan 03, 2014 3:43 pm
Location: Estonia

Math channel formulas

Post by volrem » Sat Sep 27, 2014 9:08 am

Hi


I'm trying to create math channel to display wheel speed in km/h.

My sensor trigger wheel has 48 teeth so with freq(A)/48*60 i get rounds per minute and that function works.

But to put it into km/h I need to multiply that with wheel circumference which for 205/55R16 tyre is 1985mm.

Result will be in mm/minutes but i need to convert it to km/h. 1985mm/minutes equals 0.1191 km/h.

So my formula should look like this: freq(A)/48*60*0,1191 but that doesn't work for me. I get this result:
1.PNG
Also tried this one: freq(A)/48*7,146 (60*0,1191=7,146) and this gives bit different results but still not ok.

If i use integer [ freq(A)/48*7 ] then i get correct results but since it's rounded i can't get accurate enough.
2.PNG
I tried using . instead of , but get red error or pico crashes. Also tried parentheses in several ways but no success. What i'm doing wrong and is it possible to use numbers with . or , ?

Also tried formula listed in http://www.picotech.com/picoscope6-maths-channels.html but get red X.

Image

volrem
TwoWaves
TwoWaves
Posts: 231
Joined: Fri Jan 03, 2014 3:43 pm
Location: Estonia

Re: Math channel formulas

Post by volrem » Sat Sep 27, 2014 12:15 pm

Today is "answer your own question day" but perhaps helps someone else also.


Anyway i got it sorted after reading picotech forum. Noticed thread there about "Comma as decimal point".
My system also uses comma as decimal point so that's why i have had troubles with math channels from the beginning.

I followed instructions in this thread and now use . as decimal point. Everything works now.

http://www.picotech.com/support/topic14379.html

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Robski
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Location: Yorkshire

Re: Math channel formulas

Post by Robski » Sat Sep 27, 2014 2:14 pm

I read that post a while ago & if it wasn't for that you would be doubting yourself & your formula just for yet another bug in the software..............it proper twists my melons :x

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