digital electronics

Discussion in 'General Electronics Chat' started by james7701, Mar 3, 2016.

  1. james7701

    Thread Starter New Member

    Jan 5, 2016
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    how can i use this formula to calculate the frequency in the correct manner?
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    f=1/T=1/10 ms=1/0.01=100 Hz
     
    Last edited: Mar 3, 2016
  3. james7701

    Thread Starter New Member

    Jan 5, 2016
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    milliseconds are smaller than seconds so, it needs to be converted?
     
  4. ISB123

    Well-Known Member

    May 21, 2014
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    Yes,1000ms is 1sec.
     
  5. james7701

    Thread Starter New Member

    Jan 5, 2016
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    so, from the last zero u count 3 times to the right <--- to get 0.01? or do u have a chart to show the conversions?
     
  6. ISB123

    Well-Known Member

    May 21, 2014
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    if 1ms=0.001 than 10ms=0.01 .
    I just know the conversion in my head didn't really do anything mathematical.
    You just need to know that 1s is 1000ms.
     
  7. Veracohr

    Well-Known Member

    Jan 3, 2011
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    When dividing by powers of 10 move the decimal one place to the left for every 0.

    So 1/10 is 0.1
    1/100 is 0.01
    1/1000 is 0.001

    Etc.
     
  8. james7701

    Thread Starter New Member

    Jan 5, 2016
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    so 1÷10000= 0.0001?
     
  9. ISB123

    Well-Known Member

    May 21, 2014
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    One second is made out of 1000 milliseconds. So its 1/1000=0.001
     
  10. james7701

    Thread Starter New Member

    Jan 5, 2016
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    so ,when it's stated that the frequency of a pulse waveform is the reciprocal of the period, that means that the time (in some form of seconds)must be converted to get the correct frequency?
     
  11. james7701

    Thread Starter New Member

    Jan 5, 2016
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    okay yes got it... thanks :)
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    Let's take it in two steps.

    First, do you know that 1 second is the same as 1000 milliseconds?

    If not, then you first need to get comfortable with unit prefixes in the SI system.

    http://physics.nist.gov/cuu/Units/prefixes.html

    https://en.wikipedia.org/wiki/Metric_prefix

    For the most part, the only ones you really need to be fluent with are the powers of 10^3, which are

    10^12 pico
    10^-9 nano
    10^-6 micro
    10^-3 milli
    10^3 kilo
    10^6 mega
    10^9 giga

    You also want to be comfortable with 10^-2, which is centi, because of the widespread use of "centimeter", though it isn't used for much else these days (at least not directly).

    Once you have that down, the second part can be handle by just remember that if you multiply anything by 1 then you don't change it's value and that if you divide 'a' by 'b' and if 'a' and 'b' are equal then the result is 1.

    So if

    <br />
f \; = \; \frac{1}{T}<br />

    The T isn't just some time, it is the amount of time for one cycle of the waveform. So if one cycle takes 10 ms, T is not equal to 10 ms, it is equal to 10 ms-per-cycle, or 10 ms/cycle.

    <br />
f \; = \; \frac{1}{T} \; = \; \frac{1}{10 \frac{ms}{cycle}} \; = \; \0.1 \, \frac{cycle}{ms}<br />

    Now, since 1 s is equal to 1000 ms, if we divide one by the other we just have 1, which we can multiply our equation with and not change the value.

    <br />
f \; = \; \( \0.1 \, \frac{cycle}{\strike{ms}} \) \( \frac{1000 \, \strike{ms}}{1 \, s}\) = \; 100 \, \frac{cycle}{s}<br />

    Finally,

    <br />
1 \, Hz \; = \; 1 \, \frac{cycle}{s}<br />

    So we can do this again (multiply our equation by the ratio of two things that are equal) to get

    <br />
f \; = \; \( 100 \, \frac{cycle}{s} \) \( \frac{1 \, Hz}{1 \, \frac{cycle}{s}} \) \; = \; \( 100 \, \frac{\strike{cycle}}{\strike{s}} \) \( 1 \, \frac{Hz \, \strike{s}}{\strike{cycle}} \) \; = \; 100 \, Hz<br />
     
  13. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The International System of Units (abbreviated SI) is the system that describes quantities and numerical relationships in science and engineering. These are the guys that define that 1/1000 of a second is called a millisecond, and is abbreviated ms, and one billion gigabytes is called an Exabyte, and is abbreviated EB. It started out as the metric system, and has expanded to cover all weights, measures, quantities, etc.

    https://en.wikipedia.org/wiki/International_System_of_Units

    ak
     
  14. Veracohr

    Well-Known Member

    Jan 3, 2011
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    Perhaps you should look at the definition of frequency: the number of cycles per second. 100Hz = 100 cycles/second. The period (T) is the time one cycle takes, so divide 1 second by 100 cycles (1/100) = .01 seconds per cycle.

    1/100 = .01
    1/.01 = 100

    So the period T=1/f, and the frequency f=1/T.
     
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