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4 votes
Accepted

How to Read Unipolar Square Waves on TRMS Multimeter

262V peak unipolar (0V/262V) square wave will have an RMS value of 262/\$\sqrt{2}\$ = 185V. However the meter may actually be AC-coupling the input and measuring the RMS value of that. So you would ...
Spehro Pefhany's user avatar
1 vote

Driving 50 Ω coax cable for doing measurements with oscilloscope

In you previous question, in bold you wrote: I'm not talking about RF That makes a great deal of difference. If what you are measuring is low frequency or DC, then the transmission line ...
Math Keeps Me Busy's user avatar
4 votes

Using 50 Ω coax cable instead of passive probe

For a good balance of input impedance and capacitive loading, you can use 50 ohm termination and a series resistor at source end. For example 950 Ω resistor gives 1:20 attenuation and a consistent 1 ...
jpa's user avatar
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1 vote

Oscilloscope: when to use coaxial instead of probes?

The cable for an oscilloscope probe (connected to the a high impedance oscilloscope input) is (generally) not a standard coax cable. If it were, say, a standard 50 \$\Omega\$ coax cable, then when a ...
Math Keeps Me Busy's user avatar
3 votes

Using 50 Ω coax cable instead of passive probe

A passive probe is more than just a 9 MΩ resistor and a piece of coax. First of all, since both the input of the scope and the coax have significant capacitance, there is a compensating capacitor in ...
Dave Tweed's user avatar
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8 votes
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Using 50 Ω coax cable instead of passive probe

Yes, you can do it. However.. the capacitive loading is fairly high on small coax cable. Maybe ~100pF per m for 1.13mm⌀ cable. So if you connect it to anything with fast-ish edges it will load the ...
Spehro Pefhany's user avatar
3 votes

Using 50 Ω coax cable instead of passive probe

The DC resistance of a coax cable is usually somewhere between 0 and 5 Ohms per 1000 meter. So yes, when you configure your scope to high input impedance, your proposed setup works out fine.
Stefan Wyss's user avatar
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0 votes

Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?

Various theories/qualified guessing: It kind of looks like noise from mains since it isn't in sync with the PWM signal. You live in North America 60Hz? A crappy power supply could be the culprit. ...
Lundin's user avatar
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0 votes

Why would changes in the impedance of a transducer affect the voltage displayed on the oscilloscope?

Changes in the transducer impedance should be downstream of the oscilloscope, right? When it comes to classical circuit analysis we don't consider the term "downstream" because it is ...
Andy aka's user avatar
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2 votes
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Bridge Tied Load Amplifier Measurement - Oscilloscope Probe Ground Reference

Normally the output of a bench power supply will be "floating" (not referenced to Earth Ground). The Earth terminal on the supply is provided for convenience, in case the user does want the ...
Peter Bennett's user avatar
1 vote

Bridge Tied Load Amplifier Measurement - Oscilloscope Probe Ground Reference

Case of the amp is not earth if only wires you connected to it is the power supply which is does not have earthed output but floating. So your setup 2 cannot work as it does not power the amp. And the ...
Justme's user avatar
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0 votes

Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?

There is a power switching device close by, which interferes here. But the receiver circuit of this encoder signal should be able to deal with this kind of common mode noise, at least if it is a true ...
Jens's user avatar
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1 vote

Why is my encoder showing abnormal spikes on the oscilloscope readings? Any suggestions on what might be causing it?

I would suspect ground connections. I presume the cable between the encoder has "ground" or "common" conductor(s). I would check to see if they are intact and connected at both ...
John Doty's user avatar
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6 votes
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Is there anyway to estimate the time average power without knowing the power factor?

P = Vrms · ​Irms​ · cos(ϕ) The above is true theoretically for sinewaves with no harmonics, no non-linearities and an ability to measure the phase angle between voltage and current. In other words it'...
Andy aka's user avatar
  • 464k
3 votes

Is there anyway to estimate the time average power without knowing the power factor?

The whole point of the power factor is that it's the factor between what the power into a purely ohmic load given the observed sinusoidal voltage (or current) is. So, no. Without the info you'd need ...
Marcus Müller's user avatar

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