Real world testing with a frequency-pulse tester?

Discussion in 'General Electronics Chat' started by steward, Oct 21, 2014.

  1. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Its seems like one step below an oscilloscope meter is a multimeter that that has a Frequency Counter ability.

    Can anyone share some real world experiences with a Frequency Counter? I just ordered online a Fluke 325 which has the Frequency Counting ability. VFDs & current quality verification are two that come to mind but practical examples of where it actually helped in real world situations would be nice. The below coin mech pulse verification is also a priority for wanting to understand more about the frequency & pulse counting capabilities of a meter such as the Fluke 325.

    I do work with a variety of coin & bill acceptance devices so I am hoping there is a way to use it to verify the length & number of the pulses being emitted. Coin mechs have 2 different methods for pulsing. I am pretty sure that the pulse detection will be no problem with the Class C relay style of pulsing but not so sure on the type of pulse that just uses one output wire & where the receiving circuit detects a momentary short to ground of the current.

    Mike
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    my fluke would have been helpfull wo9rking on bill acceptors.the frequency test function on the model 87 reads audio type frequencies quickly. older counters would have to count for a while to read the frequencies form 1's and 5's.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    The 325 is a clamp-on meter that has a "frequency" function from 5Hz to 500Hz. It does not have a "count" function.

    Ken
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Counters measure frequency, and some measure time interval. An oscilloscope can measure that, along with pulse shape, duration, voltage, missing pulses, etc. A scope (particularly a digital scope) is much more useful than a frequency counter for general electronics use.
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    I made a 9.99999Mhz frequency counter and expanding to 90Mhz, I borrowed a 500Mhz frequency counter from a friend, and bought an IWATSU 100Mhz oscilloscope also can be measure the frequency.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    My DMM has frequency measurement.
    I cannot recall when I have ever made use of it.
    Instead, I would use an oscilloscope or a frequency meter if I really needed to know the frequency.
     
  7. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken & others,

    It seems like that lack of a counter feature would be more of an issue for someone verifying continuous count from a sensor on the output from some of the modern extra fast coin or bill counting machines. I agree that a full featured oscilloscope would give a lot more information than just a meter with just the limited range more basic frequency measuring function. I suppose an oscilloscope could be improvised ??? to work with the totally non invasive approach like the Fluke 325 clamp on meter.

    Someone correct me if I am wrong but it seems like I will gain the ability to observe the frequency change as each 50-150 millisecond pulse occurs. I know with my Fluke 12 that I used for basic testing for over 20 years ... it would not show a response on the meter because of too short of a duration of the pulse when I was attempting to observe a change on its display. Another factor could have been the fact that the Fluke 12 was not a True RMS meter ... I am not sure.

    I have not received the Fluke 325 that I bought online yet; but it seems like it will at least show a quick display of 500Hz when a 50 millisecond pulse occurs. I am hoping that it will go to a momentary OL on the display when each 150 millisecond (1500 Hz) occurs.

    I appreciate the dialog on this.

    Mike
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    A frequency meter displays the frequency of a continuous repetitive signal.

    If the meter receives a single 50ms pulse the meter will display zero.

    If the meter receives repetitive pulses 50ms apart the meter will show
    1/0.050Hz = 20Hz.

    A frequency function on a handheld meter would not be useful for counting coins in a coin operated machine.
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    some counters have a period function, that measures the length of pulses. a lot of dedicated counters, while they will go to very small increments, will take quite a while counting to get to even .01 hz resolution. the counter in my fluke has a sort of prescaler in it that multiplies the incoming signal so it can display in real time, instead of taking 100 seconds to dis;play to .01 hz resolution. that is usefull when measuring audio frequencies when you dont have all day. like testing private line tone codes on radios.
     
  10. steward

    Thread Starter Active Member

    Jan 21, 2011
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    MrChips & others,

    I won't know until I physically test the new Fluke 325 meter after I actually get it. The above information is actually encouraging since all of the very numerous coin & bill validators that I work with have multiple pulse outputs per coin. So it appears that the basic (albeit limited) information wanted in terms of a consistent reading per pulse will possibly show on the display. The very few coin & bill validators that I have that are set on the MDB output are less likely to show a reading ... I am not sure ... some of those specific ones have ribbon cables which could hamper the "more noninvasive" clamp on ability.

    Thirty five seconds into the following 3 minute YouTube somewhat depicts the quick continuous 4 pulses from a dollar coin. In the case of larger denomination coins such as a Toonie or a larger denomination bill ... there could be an even more helpful longer duration display of continuous individual pulses. Maybe dividing the time duration could show the actual number of the consistent change that occurs within the switch leg wire???

    I am hoping there is a work around with the "frequency function" or another function so a "counter function" won't be critically needed. It seems like there are tricks such as more physical wire loops when it comes to clamp on meters.

    Mike

     
    Last edited: Oct 23, 2014
  11. steward

    Thread Starter Active Member

    Jan 21, 2011
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    I received my new Fluke 325 & Ken is right ... the display did not show any Hz frequency when I clamped over the wire from the bill validator to the input for the pulse output wire of the validator. I even put in a $20 bill to maximize the number of pulses that were carried by that specific wire.

    So I if it is important enough to me ... I guess I will have to buy an oscilloscope or at minimum use some type of a clamp on a wire counter that will be compatible with those types of pulse outputs that I previously described. Whether AlfaCliff's Fluke 87 would be the best fit for the counting purpose ... I would have to study what is involved more. On some of the equipment that I work with the pulses are 5vdc & since I invested in a calibrated Fluke 771 for detecting minute amounts of current ... that could turn out to be something quick to use ... but still not as good as an oscilloscope.

    I mostly bought the Fluke 325 meter because it has the functions I use the most & my 20+ yr old Fluke 12 quit working. Also, the meter amp ac/dc range was what I needed to verify some milliamp verification for our O-3 that showed on the previously posted 3 minute preliminary visualization. The OPTO relay that we planned on using & that would fit on the PCB was rated too low at only 300ma. The tests showed as high as 660ma passing through. So it probably makes the most sense to just go with an external relay with O-3 being a 24vac output for the external relay instead of the OPTO relay.

    Mike
     
  12. MrChips

    Moderator

    Oct 2, 2009
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    If you simply want to display the number of counts going by, you can build a simple counter circuit operating off a 9V battery.
    This would make an excellent exercise and project in digital logic theory and construction. Total cost is under $10.
     
  13. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    There are a lot of counter kits out there for less then $25.

    Ken
     
  14. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Thanks for the replies but I was really hoping to see if any clamp on meter has the ability to counts pulses that would allow a troubleshooter to avoid the use of probes &/or having to put a multimeter in series. That seems like the inability to clamp on would also be a disadvantage of using an oscilloscope.

    I will say this: I went to the workbench this morning & I did learn that my Fluke 771 would at least show between 1 & 3 milliamps for the duration of pulsing ... which I guess some information could prove to be better than nothing. The Fluke 771 was not quick enough to show just one pulse though. It seemed like the time duration for the 1-3 milliamps on the display was in proportion to the number of pulses. I tried $20, $10, & $5 bills along with $1 coin to generate the multiple pulses. With one quarter there was just one pulse & there was no response because apparently the 50ms to 150ms was too quick for the meter when it was just a singular pulse & not continuous pulsing.

    I see by some of the reviews on the Fluke 902 with its micro amp capability that it could possibly show each individual pulsed blip of current. I wonder if the Fluke 902 micro amp capability would also be able to detect stray current on a POORLY designed OEM printed circuit board? That is the main reason why I bought the Fluke 771. Anybody have experience with detecting minute amounts of stray current on POORLY designed OEM printed circuit boards? I know there are grounding technicalities but sometimes I really wonder once those appear to be verified with ohms testing etc. It seems like a clamp on meter capable of detecting minute amounts of stray voltages could help in correcting the problem of some control boards. This might be a whole new topic & possibly has been covered in depth before???

    Mike
     
  15. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Last edited: Oct 27, 2014
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