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2247A Is this normal?


Tim / N8TIM
 

Hello All
I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak the cursers are not touching the peaks of the wave form. Is this normal or do i need to get the service manual out?

https://groups.io/g/TekScopes/photo/259345/0?p=Created,,,20,2,0,0

Thanks


Dan G
 

On Wed, Jan 13, 2021 at 03:10 PM, Tim / N8TIM wrote:

I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak
the cursers are not touching the peaks of the wave form. Is this normal or do
i need to get the service manual out?
Hi Tim,

The signal you are measuring seems to be close to 110 MHz, which is at the
BW limit of the 2247A. The exact vertical deflection bandwidth of the
scope is unlikely to be exactly the same as the bandwidth of the peak-to-peak
detector, which may be somewhat higher.

I have a 2246 Mod A (well-calibrated to the best of my knowledge), which
shows similar results when measuring a 110 MHz signal from the SG503.
In reality, the signal amplitude is somewhat greater than indicated even by the
p-p detector.

Do you know the actual amplitude of the signal you are observing? (A 100 MHz
scope cannot be used to accurately measure the amplitude of a 100 MHz signal)
At 100 MHz, one would expect a measurement error close to -3dB.

By itself, your photo is not necessarily an indication of any problems with your scope.
Are the cursors closer to the waveform peaks when you measure a 25 MHz sine wave?


dan


Tom Lee
 

Hi Tim,

Have you read the fabulous manual? [Who reads manuals??]

The peak-to-peak function of the voltmeter in the 2247A is spec'd to 25MHz, according to Tek. Try making a measurement within that bandwidth and see what you get.

When it comes to using an instrument you intend to rely on, it's a good idea to study the specs to see where, and where not, it is going to be reliable. That way, you'll know what to expect, and know when there's a real problem.

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/13/2021 09:39, Tim / N8TIM via groups.io wrote:
Hello All
I have a 2247a and when I put it in the voltmeter mode and pick Peak to Peak the cursers are not touching the peaks of the wave form. Is this normal or do i need to get the service manual out?

https://groups.io/g/TekScopes/photo/259345/0?p=Created,,,20,2,0,0

Thanks




Tim / N8TIM
 

You are correct. It was at 110Mhz. I had just had my SG at that Freq for something else when I hook it to the scope and noticed the Peak to Peak reading. I attached a link to the two screen shots at 25Mhz. It looks to be correct. The curser are just off a little. Thanks all for you help.

https://groups.io/g/TekScopes/photo/259345/0?p=Created,,,20,2,0,0


tekscopegroup@...
 

When that happens to me, I usually increase the screen intensity and then I can see that there was either some pulses or noise on the signal that go beyond the signal and are what actually are defining the position of the cursors, and where invisible under normal intensity conditions. Other than that I find the voltmeter function very accurate and useful.


nielsentelecom@sbcglobal.net
 

Tom,

What is the P-P frequency response spec referred to as? I have a 2246A. I would think it is the same as a 2247A.