INTP:
Think of it as an investment.If you charge 3 people $5 to use whatever it is you're building, it will have paid for itself.
$15 for 'exactly what you need' sounds pretty cheap.
for 15$ I wil get over that that I will get plot after I make full log. For this that i building real-time graph is only a "luxury". I build it for myself there is no charge to anyone, and I am student so every cent is valuable
RoMZERO:
Do you need a real-time plot?Do you have any experience with the python language?
Yes I need real-time plot and i don't have experience with python, but I learn fast and have will to learn somethnig new.
mrburnette:
A "shareware" version is still available as a free download:
http://stampplot-lite.software.informer.comfull speed of arduino to measure RPM,
100mS is a very long time even at the old 8-bit Arduino 16MHz clock. Newer 32-bit arduinos are much faster. STM32 clones (about $4 USD) are 72MHz and fhe $3 ESP8266 can run upto 160MHz.
Ray
Thank you very much, now I must make sketch and try this program...