What Frequency Counter Should I Buy?

Discussion in 'Test & Measurement Forum' started by erictech7, May 12, 2019.

  1. erictech7

    Thread Starter New Member

    Mar 23, 2015
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    I am looking for a frequency counter but am not sure what features I should look for, or type, etc.

    I am a hobbyist, not a pro, and want it for general purpose use. One is checking RF freq's such as IF oscillators. Another would be logic and other digital chips. Audio, synthesizer circuits. Name it, I'll look at it.

    Should I get several different ones?

    If someone could give me a basic guide on frequency counters, such as whether there is a difference between RF and audio frequency counters that would be great.

    I have tried googling this information, but a lot of it is surprisingly hard to find.
     
  2. joeqsmith

    Member

    Oct 15, 2016
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    Depends what you need it for really. If you are just looking for a simple counter that can read frequency, some of the handheld meters I have looked at could read above 100MHz. I think there was one that made it to 200MHz! Not real accurate and not much resolution, but low cost.

    Do you need to read a pulse width, period, ratios, events? Do you need an interface to a PC? If you need some thing fairly accurate, you may need some sort of reference.
     
  3. erictech7

    Thread Starter New Member

    Mar 23, 2015
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    Most likely, yes.
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    I think you should be careful on choosing a frequency counter. Most frequency counters rely on an input signal that is well shaped and of strong amplitude. Connecting a frequency counter to an RF source will likely load the circuit and either shift the frequency or kill it altogether.

    An oscilloscope is a superior test instrument for checking AF and RF signals. It can also give you frequency information.

    Use a frequency counter when you want high accuracy, such as 8-decimal place precision.
     
  5. erictech7

    Thread Starter New Member

    Mar 23, 2015
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    Yes, I have seen some ads for RF frequency counters, which is one reason I posted this. So is it possible to use an RF frequency counter for non-RF freq's?

    I also have seen references to "universal counters". Is there a real difference between these and counters in general?
     
  6. crutschow

    Expert

    Mar 14, 2008
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    I agree with MrChips.
    An oscilloscope is likely better for your requirements unless you need higher precision and accuracy of the frequency.
     
  7. erictech7

    Thread Starter New Member

    Mar 23, 2015
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    I know you want to save me money, but I want a frequency counter.

    Help me, don't hinder me.

    And I have an oscope.
     
  8. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    It sounds like you either did not read o-scope manual or you need a well written one (some of them are so dry that they would put person to sleep so quality of writing is important).
     
  9. SamR

    Member

    Mar 19, 2019
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  10. joeqsmith

    Member

    Oct 15, 2016
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    Well, if it works, it will certainly do what the manual claims. I have two dedicated counters for my hobby work. One is for sub GHz. The other for higher. The lower frequency unit has the features I mentioned. It has multiple channels that can be locked together or used independently. For example, it can trigger on the rising edge of channel 1 and the falling edge of channel 2 then measure the time between these two edges. These two edges could be the same signal or not. If it is the same signal, you can select this rather than route cables to both channels. The low speed channels on both of my counters can be selected for 1Meg or 50ohms. The higher speed counter can go up to 500MHz with the 1Meg input selected. I will use them from time to time with a 10X or a FET probe. Both are tied to a GPS that is used for their reference.

    Having these features makes it more useful. Here you can see me using it characterize my camera's trigger.


    You can find old name brand equipment like this fairly cheap, if you like referbing vintage equipment and have the skills needed. Pretty much all of my test equipment is what I would consider vintage.
     
  11. eetech00

    Senior Member

    Jun 8, 2013
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    Hi

    I’m in market for a counter as well.
    From what I’ve seen is the cost goes up as the lower frequency limit goes down. A scope is an obvious alternative but some won’t measure really low frequencies. An example is to measure the output period of a Long timer..

    eT
     
  12. crutschow

    Expert

    Mar 14, 2008
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    Then buy one that will measure the maximum frequency you need.

    For RF you will either need a dedicated RF counter, or a buffer amp that will take the low level RF signal and amplify to what the counter needs.
    Does your oscilloscope have a amplified vertical output signal port? (What oscilloscope do you have?)
     
  13. bertus

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    Apr 5, 2008
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  14. erictech7

    Thread Starter New Member

    Mar 23, 2015
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    I know I can read freq's on an oscope. Or do the math to figure it out.

    I bought a Rigol MSO, and the manuals are basic, don't go too deep into the use of the scope. They are not like Tektronix manuals (I have an old manual for an 454 or something like that) which includes schematics for each part of the scope, how the circuits work, etc. Rigol is nowhere even close to that. It has the most basic instructions, turn on, use for class 1 or 2 measurements, use these probes for this, these logic probes for that, and not much more than that. Onboard help menu is ok, but they are not going to show you how to setup for testing. So on and on. I am not worried about that. I can figure it out.

    I am not a complete newb. I am familiar with test equipment, I was a tech in the Navy, went through BEE. That was 20 + years ago, I was not a radio tech, I was a sonar tech. I hardly got to use test equip, most testing was setting controls, see what I get. Push a button, make sure system cycles through all audio transmit beams, push another button , look for error codes, . Etc,. I know enough to know what I want, just not the subtle differences. Not to mention oscope technology has changed a LOT.

    I don't know why I have to qualify myself before I get a straight up answer.
    So now... freq counters.

    I know I will need one eventually, It has taken a long time to find out about them as it is, when I need greater accuracy than my scope can give me, I'd like to have one on hand.
    I do not want to wait too long while I do my research then to buy one.

    Please... If you don't have a helpful answer, that is OK, just don't post.

    Please, no clutter. I have to wade through the replies.

    I saw that that someone further down posted something useful. I just wanted to make very clear what I want on this thread.
     
  15. Yaakov

    Well-Known Member

    Jan 27, 2019
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    to understand better why you want a frequency counter, could you explain what your oscilloscope lacks that you hope to add with a counter?

    EDIT: Please ignore this question. Thanks.
     
  16. crutschow

    Expert

    Mar 14, 2008
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    The Rigol MSO oscilloscopes apparently have a source output that could be used as a preamp for RF signals to the counter, as shown below:

    upload_2019-5-12_12-47-13.png
     
  17. joeqsmith

    Member

    Oct 15, 2016
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    I don't know what a long timer would be to you but my counter can easily read periods in the minutes. Funny thing is a few years ago, I saw a several of these counters get tossed out. They were free and still there were very few takers. My guess, people just wanted new equipment.

    Sensitivity is 25 mV rms for DC -40MHz and 50mV for 40MHz to 100MHz. The higher frequency input's sensitivity is 15mV for 5MHz to 512MHz and 20mV for 90MHz to 1.3GHz. These numbers are conservative. Attached, I measured the threshold where the counter would just start to read at 100 and 1000MHz. Then again, the noise floor of my scopes are in this range..

    100M_4p63.JPG 1G_21p4.JPG
     
  18. MrChips

    Moderator

    Oct 2, 2009
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  19. SamR

    Member

    Mar 19, 2019
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    Do you have a digital signal generator and does it have an external input? If so what are the specs on it?
     
  20. Reloadron

    Distinguished Member

    Jan 15, 2015
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    With a focus on a Frequency Counter and only a frequency counter I would sit down with a blank sheet of paper and a pencil with a good eraser and start listing the features you are wanting or need. Measure RF is too general so I would start with measure RF to what frequency? What functions would you like? Things like Freq, Ratio, Time Interval, Period, and others. How about Resolution? Then we also have the uncertainty or accuracy. There is a heck of a list and don't forget sensitivity.

    On the bench I use an old Fluke 7250A Universal Counter/Timer and while old and limited to 80 MHz it is a good little general purpose counter timer. I also have an HP 5334 which sits on a shelf in the basement. While the HP is by far the better counter the little Fluke 7250A fulfills just about all of my basic bench needs.

    Once you have a good handle on the features you need or want I would look around on Ebay and similar at used test equipment as I see has been mentioned. Many can be had pretty inexpensive, I see the little Fluke unit I mentioned for about $80 or less on flea bay.

    Ron
     
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