How do I test an oscillator?

Thread Starter

Circuits123

Joined Dec 7, 2012
93
I need to test a 5V, 1MHz oscillator 14-DIP. I don't have an oscilloscope. Can I do it with a PC-based/sound card oscilloscope? And, if so, how?

EDIT: Here's a link to the part:
https://www.digikey.com/products/en?keywords=ctx775-nd

I'm trying to make an AM transmitter with tubes but I'm concerned that I accidentally fried it. The only test equipment I have is a multimeter (digital and analog). I Googled diode probes and it looks like they can't handle more than 50V (at least the ones I found). I think that means it won't work on my circuit, unless there's an easy alternative I could build just for testing purposes.
 
Last edited:

dendad

Joined Feb 20, 2016
4,451
Some real detail will help.
Is this just a chip or a module? Circuit? Photo????
What is the expected output level?
What test gear do you have?
Do you need to test frequency, stability, waveform, level???

A simple test for output level is to use a Diode Probe on your multimeter.
Google "Diode Probe" for a very simple add on to make.
Then you could tune an AM radio to 1Mhz to listen for it.
 

spinnaker

Joined Oct 29, 2009
7,830
Depends on what you mean by test. 1 MHz is dead center in the middle of the AM broadcast band. Any AM radio will tell you if the part is awake.

ak

Wow that is bringing a flash back to my memory. I am trying to recall where I have used an AM radio in the past for troubleshooting. I seem to recall using one fairly regularly. Perhaps it was to troubleshoot oscillators in other radios? Or maybe television?? But I just can't recall for sure.
 

bushrat

Joined Nov 29, 2014
209
Last time I used AM radio was for testing AN/TRN-30(V)1 beacons. Granted, the output frequency was only half of am freqs, but it was enough to hear the morse code....and that was still in 2005.
 

Dodgydave

Joined Jun 22, 2012
11,284
If you have an AM radio , tune it to 999Khz, and hold the oscillator near to the radio , it should emit a 1Khz tone if your oscillator is working.
 

LesJones

Joined Jan 8, 2017
4,174
Dave,
That would not work with an AM receiver (Unless there was a radio station on 999Khz or 1001Khz.) It would work with an SSB receiver.
Many years ago there were quite a few standard frequency transmitters on frequencies such as 5.000000 Mhz that you could beat with a frequency source that you were testing using an AM radio to check it's accuracy. If these transmiters still exist the TS could check the accuracy of his 1 Mhz oscillator as it gives a square wave output which would contain many odd harmonics. As he would be looking for a zero frequency he would need to connect a mulimeter to the AGC line of the AM receiver and watch the voltage varying at the beat frequency.

Les
 

takao21203

Joined Apr 28, 2012
3,702
If you have an AM radio , tune it to 999Khz, and hold the oscillator near to the radio , it should emit a 1Khz tone if your oscillator is working.
that would be pretty bad bcz youd get low frequency noise all the time unless you tune exacctly to 1 MHz. Am I wrong or is it the HF is modulated out? Maybe you could get a very weak tone somehow.

Isnt it when using AM, the strength of the carrier is modulated with the LF, the HF is modulated out?
How can you get beat frequency without a local oscillator I dont know.

An alternative would be just any PIC microcontroller with a simple blinking LED but guess the TS would know already.

These are handy to make AM transmitter only point is they are quite expensive.

i made AM transmitter some day with 500 KHz resonator and it was quite bad, used a wire antenna and could get a metre at best. But it worked wireless with 2xAAA batteries and several transistor.

So TS I suggest, you build a proper AM transmitter with 500 KHz resonator, and then instead, inject the 1 MHz signal somehow, could remove a few parts perhaps since amplifier for oscillation not needed.

Or get some 16F5X my favourite the 16F59, theyre quite basic parts not much to learn but highly useful and dont need to become anxious about hundreds of configuration bits and registers. Then youll be equipped to test crystals and crystal oscillators if they work (LED blinks or not).
 

dendad

Joined Feb 20, 2016
4,451
As you tune across the 1Mhz on an AM radio, you will hear the background noise go to zero. You may hear a beet depending on near by stations. Turn the 1Mhz osc on and off to make sure it is going and that is what you are listening to.
 

Reloadron

Joined Jan 15, 2015
7,501
While I don't have what you have I do have an old Dale Manufactured (now Vishay) XO-43B Clock Oscillator 1 MHz version. With 5 VDC applied I get out a 4 V peak to peak square wave which is what these things are designed for. Less a scope or other test equipment, using an AM radio in real close proximity you can pick the signal up as mentioned. I hung about 30 cm of wire on the output to serve as an antenna. About all this will tell you is if it is working (oscillating). Keep in mind these things are designed to work into a very high impedance.

I'm trying to make an AM transmitter with tubes but I'm concerned that I accidentally fried it.
Again, the output of these devices is a square wave, they are commonly called clock oscillators. If you want to look at your signal on a scope I suggest a circuit as Danko suggest in post #8 or do a Google of RF Probe Circuits. I also suggest using germanium diodes like the old 1N34 if you can find some. Anyway, remember you have a square wave and not a nice sine wave output of your oscillator.

Ron
 

danadak

Joined Mar 10, 2018
4,057
Can I do it with a PC-based/sound card oscilloscope? And, if so, how?
Unfortunately no, sound card sample rate simply not high enough.

But the sound card scopes still useful around audio frequencies, plus
spectrum analyzer and signal generation.

https://www.zeitnitz.eu/scope_en



http://www.instructables.com/id/Use-Your-Laptop-as-Oscilloscope/

http://www.zelscope.com/

http://www.ledametrix.com/oscope/

http://www.virtins.com/downloads.shtml


But first build a simple circuit to protect sound card inputs so you do not
ruin from transients, overvoltage. Google "protect sound card input".


For example http://makezine.com/projects/sound-card-oscilloscope/


Sound card impedance bridge -

http://www.marucchi.it/ZRLC_web/ZRLC/Steber_An_LMS_Impedance_Bridge.pdf

http://www.sillanumsoft.org/ZRLC.htm


Regards, Dana.
 
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