just would like to ask

Discussion in 'General Electronics Chat' started by blue6x, Apr 15, 2005.

  1. blue6x

    Thread Starter Active Member

    Apr 6, 2005
    38
    0
    If I have a tachometer or rate meter, and I applied a relatively known frequency of 50Hz as signal input, what can I expect in the output to be read by the display, assuming that the reading is in pulse per revolution.

    I am asking because in one set of tachometer that I tried to use, the reading is about 3000 more or less, but that is in revolutions per minute or cm/min.

    Can anyone here please answer my question. I've use a digital tachometer to measure the speed of 50Hz iand the result is somewhat in between 7000 and 8000 pulse per revolution. I just don't know why it happened.

    Anyone please. Thanks. The tachometer I used is F90 from line seiki co. Thanks again ang more power...
     
  2. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1
    I couldn't find anything on the web about Seiki tachs. However, most tachs are field programmable / calibratable. This means that you can set up what you want your output to be based on a given input. Check any literature you have on your instrument and see if there are dip-switches that need to be set, or perhaps pots that can be tuned.

    Remember too, that you're trying to use a tachometer to measure frequency. Speed and frequency are not the same thing, and the tach meter may never work for this application.
     
  3. blue6x

    Thread Starter Active Member

    Apr 6, 2005
    38
    0
    there is relly dip switches present in the circuit, for an open collector input, this switches are off, there is lso a set of combination for magnetic sensor input and voltage input, I'm trying to look for connections with any formula that would lead me to the answer. The input is actually fed up to a microprocessor, and whatever my input for the dip switches, the frequency that I measure is still 5o Hz, but the reading changes...

    That formula that I applied before using other tachometer use the formula f = 1/t and then iI multiplied it to 60 to get a value in rev per min, The output I obtained is near to this value. But using this rate meter or tachometer F-90 series, applying a frequency of 50 resulted to a value more than the doubled the value I was expecting using the said formula.

    Can anyone give their thoughts again.

    Thanks....
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Hi blue6x,

    Are you feeding your 50 Hz input into the relay input? If so then that may be your problem. I have some information that indicates that the relay input can only take input pulses as high as 25Hz. The relay is probably experiencing contact bounce that introduces additional pulses that will result in a higher than actual count.

    If you are using the relay input, then switch over to the voltage input and see if you get a more accurate rpm count. The voltage input should take a signal that swings from a low voltage level of +1.9V to a high level of between +3.5v and +30v.

    Good Luck.

    hgmjr
     
  5. blue6x

    Thread Starter Active Member

    Apr 6, 2005
    38
    0
    I have tried using the voltage input, one is 3.5V and the other is around 30V, the reading using 3.5V is around 11000 while 30V is around 4000-5000, how could you possibly relate this two readings. Thanks...
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    It is probably worth examining the characteristics of the signal you are using to test the tachometer. What are you using as the source of the 50 Hz input signal?

    hgmjr
     
  7. blue6x

    Thread Starter Active Member

    Apr 6, 2005
    38
    0
    It was a signl generator i think, it has a different inputs of .11 Hz, 25 Hz 50 Hz and 20kHz. I choose the 50 Hz for both the contact type nd voltage input, 3.5 V and 30 V.
     
  8. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Have you made sure that the output from the signal generator is a signal that is not swiinging negative with respect to ground? The F90 appears to want to see an input that is positive with respect to ground. If it is fed a voltage that is negative with respect to ground it may get cranky.

    hgmjr
     
  9. blue6x

    Thread Starter Active Member

    Apr 6, 2005
    38
    0
    All necessary precautions, I think, where observed. I just don't know if there was really a significant difference between a digital tachometer or perhaps I call it as rate meter, on the handheld tachometer. I've been trying to look for answers on the net if there were any computations or design parameters which could be an additional factor why I can't solve the problem, but I can't find any so far...
     
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