oscilloscope calibration

Hi Bob,

That definitely does sound like a good project. If I could do it myself, I'd rather not pay someone else. One of the sellers I came across says that the frequency of the calibration is 975mhz, and the book actually calls it a

1khz signal. Is that true? Is it bad if the person modifies the internal circuitry to reflect closer to 1khz?

I have zero experience with scopes... please excuse the ignorance.

Thanks. Mike

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Great idea... thanks.

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I assume you are talking about the voltage and frequency ranges. If so, you can probably make your own calibrator. Many scopes have a simple calibrator built in, just a square wave at 1 volt and 1 kHz or some such. You can use a crystal and some frequency dividers to get a whole range of frequencies. Use them to chop the output of a precision voltage reference. You can also make a precision divider by matching a series of resistors, or you can use digital PWM to produce a high-frequency pulse train with a duty cycle that you can set in steps.

Not only is this a good project, it's a handy thing to have around the lab.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Hi, Mike. You might want to call the local junior college or trade school and ask them where they go for calibration services.

Good luck Chris

I don't think the built-in scope calibrators should be relied on too much for frequency. Their primary purpose is to provide a nice square wave that you can use when setting the probe compensation on a 10X probe.

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Hi Mike,

I cobbled one together some years back.

If I were to do it again I would probably chop the reference voltage as suggested by Bob.

Yes, I meant 975hz -- doh.

Thanks for the input. I wouldn't think of modifying any of the scope circuitry; I was just baffled by someone else doing it.

Cheers, Mike

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I'm not sure what device the 975 Hz (probably not milliHertz) refers to. I don't advise messing with the internal circuitry of the scope, but of course if you build your own it will be as accurate as the reference crystal you use. Since scopes are usually just for visual comparisons (unless you have one of those fancy ones with counter circuitry built in), you only need to make is as good as you can resolve on the scope face. The raw accuracy of any crystal you find will probably be much better than that.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Thanks.