Frequency measurement instrument - Electronic Circuits Projects Diagrams Free

whiz115 · 16th February 2008, 05:50 PM

I found online two multimeters in very good price that can measure frequency too... i got attracted enough, because i don't have oscilloscope. The problem is that the first one was a simple multimeter capable of measuring frequency up to 10MHz and the other it had almost everything!
auto-ranging and capacitance meter up to 200uF however the frequency meter was hardly 100KHz...
So because i don't own a good multimeter and i can't afford buying a very good and expensive, i should buy this here...

http://www.uni-trend.com/UT10A.html

and i'll try to build a simple frequency meter however with bigger bandwidth around 100MHz or less.

i find it important the design to have a PCB layout... also i want an opinion for the above multimeter, it would interesting in case it can measure AC voltage in higher frequency than the very simple digital ones...

thank you!

mvs sarma · 16th February 2008, 06:21 PM

You may try to study the Frequency counter that almost touches 50MHz, from IK3OIL
the article copy is attached, and it is for personal use as per the author. this again uses PIC16F84A. I feel you need not be scary of micro-controller. Perhaps you can get a local HAM operator or any electronic component seller who could program a chip and give you. This is especially because, without a controller, one can use chips like ICL7216 etc but construction cost will boost with bulk of components needed. all those jobs are done in software in case of Micro-controller.

he has provided PCB layout and the HEX file is available. It is working fine For me. but it gives a minimum count of 10Hz
thus if you try to measure 60Hz you are likely to get 6 or +/- one count.

if our interest is low frequency like public mains frequency and audio range, we need to count up to 2 decimal points of a Hz.(1/100Hz).

Rolf · 16th February 2008, 06:39 PM

Quote:

Originally Posted by whiz115

I found online two multimeters in very good price that can measure frequency too... i got attracted enough, because i don't have oscilloscope. The problem is that the first one was a simple multimeter capable of measuring frequency up to 10MHz and the other it had almost everything!
auto-ranging and capacitance meter up to 200uF however the frequency meter was hardly 100KHz...
So because i don't own a good multimeter and i can't afford buying a very good and expensive, i should buy this here...

http://www.uni-trend.com/UT10A.html

and i'll try to build a simple frequency meter however with bigger bandwidth around 100MHz or less. When I say simple I mean if it is possible to use components that i already own (like a LCD from an old multimeter..maybe a schmitt trigger 74HC14N) then it would be great! also i'm interested to find something without microcontroler! is that possible?

i find it important the design to have a PCB layout... also i want an opinion for the above multimeter, it would interesting in case it can measure AC voltage in higher frequency than the very simple digital ones...

thank you!

The meter looks good and for only 10URO it is a bargain.
You can easily extend the range of 100khz to 10mhz by building a simple prescaler from two divide by 10 counter chips. granted it will not give you the one digit resolution but for most hobby work it should be close enough.

mvs sarma · 16th February 2008, 06:54 PM

Quote:

Originally Posted by Rolf

The meter looks good and for only 10URO it is a bargain.
You can easily extend the range of 100khz to 10mhz by building a simple scaler from two divide by 10 counter chips. granted it will not give you the one digit resolution but for most hobby work it should be close enough.

If whiz115 has already a DMM, it may perhaps be better that he assembles a counter exclusively.It may be of help if he wants to enter electronics and RF hobby .

whiz115 · 16th February 2008, 08:59 PM

guys thanks for your answers!

i'm not ready yet to mess with uCs....

the idea of a small device that can be connected with the above
multimeter looks quite interesting! mostly i care about frequencies of few MHz but i would like it if i could measure up to the FM band range, although i don't care so much for that option.

can you give me directions? PCB layouts etc?!

whiz115 · 19th February 2008, 06:25 PM

second thought... i don't understand how i can measure higher frequencies if i connect an external device on that multimeter! still the multimeter's frequency point has a limit how we suppose to overcome it by connecting something externaly?!

anyway! if it is possible i'm still interested, or at least for something else that has no uC and there is a PCB layout for it.

thanks!

Leftyretro · 19th February 2008, 07:05 PM

Quote:

Originally Posted by whiz115

second thought... i don't understand how i can measure higher frequencies if i connect an external device on that multimeter! still the multimeter's frequency point has a limit how we suppose to overcome it by connecting something externaly?!

anyway! if it is possible i'm still interested, or at least for something else that has no uC and there is a PCB layout for it.

thanks!

A simple external frequency divider (series of digital flip-flop circuits) would be able to divide the measured frequency and supply the DVM with a divide by 10 (or 100 or 1000) signal that it would then display. You then manual multiply the displayed frequency by the divide factor of the external divider. It trades off frequency resolution for frequency range. Such external dividers were very popular accessories for the early frequency counters made in the 70s and 80s. I'm sure that there are many published circuits avalible on the web.

That make sense?

Lefty

mvs sarma · 19th February 2008, 08:03 PM

Quote:

Originally Posted by Leftyretro

A simple external frequency divider (series of digital flip-flop circuits) would be able to divide the measured frequency and supply the DVM with a divide by 10 (or 100 or 1000) signal that it would then display. You then manual multiply the displayed frequency by the divide factor of the external divider. It trades off frequency resolution for frequency range. Such external dividers were very popular accessories for the early frequency counters made in the 70s and 80s. I'm sure that there are many published circuits avalible on the web.

That make sense?

Lefty

You are right. But implementing division by 10 ,100, at frequencies around and above above 100MHz( Op wants FM band frequencies)would not be cheap either.
prescalar chips and are costly. While anyhow one has to afford a prescalar chip, he could well implement a kit for frequency measurement.

wah, I have a fresh Idea. there are cheap digital scale radios from china. they are sold very cheap in dollar / pound shops. see link below.

http://www.hanssummers.com/radio/superdrg/index.htm
one can recover the display part carefully and use it as a good frequency meter, of course with an offset of 455KHz in AM bands and 10.7MHz in FM bands.

mvs sarma · 19th February 2008, 08:05 PM

Quote:

Originally Posted by Leftyretro

A simple external frequency divider (series of digital flip-flop circuits) would be able to divide the measured frequency and supply the DVM with a divide by 10 (or 100 or 1000) signal that it would then display. You then manual multiply the displayed frequency by the divide factor of the external divider. It trades off frequency resolution for frequency range. Such external dividers were very popular accessories for the early frequency counters made in the 70s and 80s. I'm sure that there are many published circuits avalible on the web.

That make sense?

Lefty

You are right. But implementing division by 10 ,100, at frequencies around and above above 100MHz( Op wants FM band frequencies)would not be cheap either.Prescalar chips are costly either. While anyhow one has to afford a prescalar chip, he could well implement a kit for frequency measurement.

I have a fresh Idea. there are cheap digital scale radios from china like kchiboo. they are sold very cheap in dollar / pound shops. and one can salvage the display part carefully and use it as a good frequency meter, of course with an offset of 455KHz in AM bands and 10.7MHz in FM bands.

whiz115 · 20th February 2008, 12:36 AM

Quote:

Originally Posted by Leftyretro

A simple external frequency divider (series of digital flip-flop circuits) would be able to divide the measured frequency and supply the DVM with a divide by 10 (or 100 or 1000) signal that it would then display. You then manual multiply the displayed frequency by the divide factor of the external divider. It trades off frequency resolution for frequency range. Lefty

is that what i want? few 74HC390 in series?

http://hobby_elec.piclist.com/e_clock4.htm

If that's the case can somebody tell me what to modify on the schematic so it can fit to my needs?

@mvs_Sarma do you find it good idea?

Leftyretro · 20th February 2008, 03:03 AM

Quote:

Originally Posted by whiz115

is that what i want? few 74HC390 in series?

http://hobby_elec.piclist.com/e_clock4.htm

If that's the case can somebody tell me what to modify on the schematic so it can fit to my needs?

@mvs_Sarma do you find it good idea?

Yes, those would work. However they need a valid logic level voltage input to work and you want general purpose frequency input capability, so a preamp circuit will have to drive the external logic divider chips to give good performance. Keep searching the web, I'm sure you will find a decent prescaler project.

Lefty

whiz115 · 17th March 2008, 03:06 PM

i'm still interested on this project but i didn't managed to find something, can somebody help me here?

i got the multimeter i'm talking about in my first post and now i want to connect something to it so i can extend the frequency measurement close to 100 MHz (recently i've made my start with microcontrolers so i don't mind if the design includes them)

btw i've noticed that the multimeter i bought is able to measure sine wave! is it possible to measure square too?

thanks!

Rolf · 17th March 2008, 04:25 PM

Quote:

Originally Posted by whiz115

i'm still interested on this project but i didn't managed to find something, can somebody help me here?

i got the multimeter i'm talking about in my first post and now i want to connect something to it so i can extend the frequency measurement close to 100 MHz (recently i've made my start with microcontrolers so i don't mind if the design includes them)

btw i've noticed that the multimeter i bought is able to measure sine wave! is it possible to measure square too?

thanks!

Here is a >50MHz counter kit for about $35. The specifications will answer your last question, I hope.
You can later add a scaler to take you as high as you can afford.

http://www.norcalqrp.org/fcc1.htm

Super_voip · 17th March 2008, 08:03 PM

The real problem with using prescalers to measure VHF is that on a multimeter you will only get a very course freq indication eg at 136.145MHz the meter will show 136.1 or maybe 136.2 so the actual freq could be anywhere in the 136.5 to 137.5 region. Check ebay I found a new meter that goes from 50MHz to 2.4GHz for $30(+post)

Rolf · 18th March 2008, 02:43 AM

Quote:

Originally Posted by Super_voip

The real problem with using prescalers to measure VHF is that on a multimeter you will only get a very course freq indication eg at 136.145MHz the meter will show 136.1 or maybe 136.2 so the actual freq could be anywhere in the 136.5 to 137.5 region. Check ebay I found a new meter that goes from 50MHz to 2.4GHz for $30(+post)

So that leaves the OP with a gap between 100KHz and 50MHz. Besides if I am looking at the correct meter they are hand held with an antenna pickup and not meant for bench work.

There is nothing wrong with scalers but in this case were the meter only counts to 3999 it would not be practical, I overlooked that in my original post. I am sure there are old Heath or B&K meters on ebay that has 7 or 8 digits and can be bought for less than $50. And if they don't go to 100MHz a divide by 10 is all that is needed.

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16th February 2008, 05:50 PM	(permalink)
whiz115	Frequency measurement instrument I found online two multimeters in very good price that can measure frequency too... i got attracted enough, because i don't have oscilloscope. The problem is that the first one was a simple multimeter capable of measuring frequency up to 10MHz and the other it had almost everything! auto-ranging and capacitance meter up to 200uF however the frequency meter was hardly 100KHz... So because i don't own a good multimeter and i can't afford buying a very good and expensive, i should buy this here... http://www.uni-trend.com/UT10A.html and i'll try to build a simple frequency meter however with bigger bandwidth around 100MHz or less. i find it important the design to have a PCB layout... also i want an opinion for the above multimeter, it would interesting in case it can measure AC voltage in higher frequency than the very simple digital ones... thank you! Last edited by whiz115; 17th March 2008 at 03:01 PM.

16th February 2008, 06:21 PM	(permalink)
mvs sarma	You may try to study the Frequency counter that almost touches 50MHz, from IK3OIL the article copy is attached, and it is for personal use as per the author. this again uses PIC16F84A. I feel you need not be scary of micro-controller. Perhaps you can get a local HAM operator or any electronic component seller who could program a chip and give you. This is especially because, without a controller, one can use chips like ICL7216 etc but construction cost will boost with bulk of components needed. all those jobs are done in software in case of Micro-controller. he has provided PCB layout and the HEX file is available. It is working fine For me. but it gives a minimum count of 10Hz thus if you try to measure 60Hz you are likely to get 6 or +/- one count. if our interest is low frequency like public mains frequency and audio range, we need to count up to 2 decimal points of a Hz.(1/100Hz). __________________ Regards, Sarma. Last edited by mvs sarma; 7th July 2008 at 01:15 PM.

16th February 2008, 08:59 PM	(permalink)
whiz115	guys thanks for your answers! i'm not ready yet to mess with uCs.... the idea of a small device that can be connected with the above multimeter looks quite interesting! mostly i care about frequencies of few MHz but i would like it if i could measure up to the FM band range, although i don't care so much for that option. can you give me directions? PCB layouts etc?!

19th February 2008, 06:25 PM	(permalink)
whiz115	second thought... i don't understand how i can measure higher frequencies if i connect an external device on that multimeter! still the multimeter's frequency point has a limit how we suppose to overcome it by connecting something externaly?! anyway! if it is possible i'm still interested, or at least for something else that has no uC and there is a PCB layout for it. thanks!

17th March 2008, 03:06 PM	(permalink)
whiz115	i'm still interested on this project but i didn't managed to find something, can somebody help me here? i got the multimeter i'm talking about in my first post and now i want to connect something to it so i can extend the frequency measurement close to 100 MHz (recently i've made my start with microcontrolers so i don't mind if the design includes them) btw i've noticed that the multimeter i bought is able to measure sine wave! is it possible to measure square too? thanks! Last edited by whiz115; 17th March 2008 at 03:12 PM.

17th March 2008, 08:03 PM	(permalink)
Super_voip	The real problem with using prescalers to measure VHF is that on a multimeter you will only get a very course freq indication eg at 136.145MHz the meter will show 136.1 or maybe 136.2 so the actual freq could be anywhere in the 136.5 to 137.5 region. Check ebay I found a new meter that goes from 50MHz to 2.4GHz for $30(+post)