Measure DC offset, Hum, DBs gain, Oscillation - Electronic Circuits Projects Diagrams Free

walters · 5th June 2005, 01:53 AM

How do i measure DC offset?

Where is DC offset mostly at on a analog or digital Circuit?

How do i measure DB gain?

How do i measure DB?

How do i measure Oscillation?

How do i measure Hum?

zachtheterrible · 5th June 2005, 02:02 AM

Mostly with an oscilloscope.

walters · 5th June 2005, 02:03 AM

Yea but how do i do it with a oscilloscope what do i do and how do i
do this stuff and measurements?

zachtheterrible · 5th June 2005, 02:08 AM

http://www.electro-tech-online.com/viewtopic.php?t=240

Take a look at that article. It gives explanations as to how to measure basic but important things on your oscilloscope, like frequency and voltage measurements.[/quote]

walters · 5th June 2005, 02:12 AM

Thanks Zach

but it doesn't show how to measure DC offset,DB gain,oscillation,hum

zachtheterrible · 5th June 2005, 02:32 AM

Well, oscillations are measured in frequency, and it shows how to do frequency.

Hum is measured in voltage usually.

DB gain gets measured by comparing the input voltage and the output voltage, or power, or current.

Dunno about DC offset.

Someone will come along shortly who knows more than me :lol:

Morgen · 5th June 2005, 02:50 AM

DC offset can be measured with a DC voltmeter or an oscilloscope. Remember that it isn't unusual, as in the case of op amp inputs, that a DC offset is in the microvolt range.

walters · 5th June 2005, 06:47 AM

Thanks guys

How do i measure overloading the input?

why does it overload the input?

eblc1388 · 5th June 2005, 09:38 AM

Quote:

Originally Posted by Morgen

Remember that it isn't unusual, as in the case of op amp inputs, that a DC offset is in the microvolt range.

Most cheap, non-precision opamps have input offset voltages in the millivolt (mV) range, that's 1000 times higher than microvolt range.

**Nigel Goodwin** · 5th June 2005, 09:56 AM

Quote:

Originally Posted by walters

Thanks guys

How do i measure overloading the input?

You don't really, you measure the output, then adjust the input level until the output starts clipping - you're VERY unlikely to overload the actual input, more likely the later stages instead - and if you DO overload the inpout stage, the later stages will be MASSIVELY overloaded.

Quote:

why does it overload the input?

Take a 5 gallon bucket, fill it with 5 gallons of water - no problem!. Now take the same bucket and fill it with ten gallons of water!, you then have very wet feet - same principle really!.

Morgen · 5th June 2005, 04:20 PM

Quote:

Originally Posted by eblc1388

Quote:

Originally Posted by Morgen

Remember that it isn't unusual, as in the case of op amp inputs, that a DC offset is in the microvolt range.

Most cheap, non-precision opamps have input offset voltages in the millivolt (mV) range, that's 1000 times higher than microvolt range.

The general-purpose uA741 datasheet shows a typical input Vos of about 2mV, whereas the precision OPA27 shows a typical input Vos of about 20uV. A 100x difference, but I get your point.
My point was only that DC offset can be a very small quantity not as easily measured as say, finding the voltage of a dry cell.

eblc1388 · 5th June 2005, 04:28 PM

Quote:

Originally Posted by Morgen

My point was only that DC offset can be a very small quantity not as easily measured as say, finding the voltage of a dry cell.

Point taken. Most often one needs to use the gain of the Opamp itself to amplify the offset voltage by 1000x to get a reasonable reading on a DVM.

walters · 5th June 2005, 06:12 PM

Thanks alot guys for your help

How do i Track down Oscillation in a circuit when im troubleshooting?

When im using the oscilloscople and i see a oscillation frequency
riding on the AC waveform what should i do to try to track down
this oscillation and where its coming from?

**Nigel Goodwin** · 5th June 2005, 07:15 PM

Quote:

Originally Posted by walters

Thanks alot guys for your help

How do i Track down Oscillation in a circuit when im troubleshooting?

When im using the oscilloscople and i see a oscillation frequency
riding on the AC waveform what should i do to try to track down
this oscillation and where its coming from?

There's no 'magic' answers, you track it down by understanding how the circuit works and what might cause it not to work correctly. This applies to pretty well all fault finding.

I would suggest you spend sometime playing with your scope and trying to understand how circuits work - you can't expect to get 5 years education in a few posts on a forum!.

As with everything, start with the basics and work up, make sure you have a good understanding of discrete components before moving on to IC's.

Morgen · 5th June 2005, 07:30 PM

Oscillation requires gain and positive feedback, so that portion of the circuit which provides those should be your focus. It would be helpful to use your scope to determine the frequency of oscillation. That information could assist in pinpointing where the fault lies. I must agree with David and Nigel, though. You seem to be overreaching yourself.
It's not that overreaching is inherently wrong. That is how we learn. But take steps too big and you'll trip up more often than learn.

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5th June 2005, 01:53 AM	(permalink)
walters	Measure DC offset, Hum, DBs gain, Oscillation How do i measure DC offset? Where is DC offset mostly at on a analog or digital Circuit? How do i measure DB gain? How do i measure DB? How do i measure Oscillation? How do i measure Hum?

5th June 2005, 02:02 AM	(permalink)
zachtheterrible	Mostly with an oscilloscope. __________________ I'm no electronics god, i just talk too much.

5th June 2005, 02:03 AM	(permalink)
walters	Yea but how do i do it with a oscilloscope what do i do and how do i do this stuff and measurements?

5th June 2005, 02:08 AM	(permalink)
zachtheterrible	http://www.electro-tech-online.com/viewtopic.php?t=240 Take a look at that article. It gives explanations as to how to measure basic but important things on your oscilloscope, like frequency and voltage measurements.[/quote] __________________ I'm no electronics god, i just talk too much.

5th June 2005, 02:12 AM	(permalink)
walters	Thanks Zach but it doesn't show how to measure DC offset,DB gain,oscillation,hum

5th June 2005, 02:32 AM	(permalink)
zachtheterrible	Well, oscillations are measured in frequency, and it shows how to do frequency. Hum is measured in voltage usually. DB gain gets measured by comparing the input voltage and the output voltage, or power, or current. Dunno about DC offset. Someone will come along shortly who knows more than me :lol: __________________ I'm no electronics god, i just talk too much.

5th June 2005, 02:50 AM	(permalink)
Morgen	DC offset can be measured with a DC voltmeter or an oscilloscope. Remember that it isn't unusual, as in the case of op amp inputs, that a DC offset is in the microvolt range.

5th June 2005, 06:47 AM	(permalink)
walters	Thanks guys How do i measure overloading the input? why does it overload the input?

5th June 2005, 06:12 PM	(permalink)
walters	Thanks alot guys for your help How do i Track down Oscillation in a circuit when im troubleshooting? When im using the oscilloscople and i see a oscillation frequency riding on the AC waveform what should i do to try to track down this oscillation and where its coming from?

5th June 2005, 07:30 PM	(permalink)
Morgen	Oscillation requires gain and positive feedback, so that portion of the circuit which provides those should be your focus. It would be helpful to use your scope to determine the frequency of oscillation. That information could assist in pinpointing where the fault lies. I must agree with David and Nigel, though. You seem to be overreaching yourself. It's not that overreaching is inherently wrong. That is how we learn. But take steps too big and you'll trip up more often than learn.