I know nothing about the scanners being discussed but I will point out the problems with using the part number of the ADC chip to predict the resolution of the scanner. The size of the ADC doesn't necessarily mean the effective number of bits of the whole scanner is the same. It is possible to trade speed for resolution by oversampling. I routinely get a solid 12 bits out of 10-bit microcontroller ADCs, for example. Of course, the opposite is the case as well obviously.
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
It certainly is.Originally Posted by onnect17
The AD9220AR is a 12-bit A-to-D converter.
The entire datasheet from Analog Devices is here: http://www.analog.com/static/importe..._9223_9220.pdf
Also the Integral Nonlinearity error is 0.5LSB, while the Differential Nonlinearity error is 0.3LSB.
This means the entire Least Significant Bit is garbage, so the device is only good for 11 bits in a real circuit, not 16.
- Leigh
If you believe you can, or you believe you can't... you're right.
Oversampling, at least in my book, will never give you a real extra bit of precision. It is more like an accepted method of estimation. But that's a different subject.
Now, if my numbers are correct, a raster line in the premier will demand around 2 Ms/sec. There is so much you can do with a 386sx cpu handling the data.
Your book may be out-of-date. I'm not sure what you are basing your criteria for bit "realness" on. Hopefully you don't ascribe extra levels of realness to bits described in datasheets. The realness of bits can only be determined by how well they describe reality. I assure you that oversampling techniques can return an effective number of "real" bits that is "really truly" in excess of those provided by the hardware. In fact, it's possible to get arbitrarily high precision out of a 1-bit ADC; not for free, but at the cost of bandwidth. And of course it's possible to get an arbitrarily low resolution out of any ADC.Oversampling, at least in my book, will never give you a real extra bit of precision. It is more like an accepted method of estimation.
The entire field of analog-to-digital conversion itself can be described as "accepted methods of estimation".
I know nothing about the Aztek scanners or how they are designed. I'm just pointing out the problems with looking at the ADC chip on the board of a scanner and using that by itself to make any inferences about the effective resolution of the scanner system, which could be lower than, equal to, or greater than the "datasheet resolution" of the ADC chip.
I attached a slide showing how I put oversampled bits to good use in brewing beer. Thanks to oversampling, you can see the cycloid-pattern signal caused by my circulation pump kicking on and off, all happening within the space of the ADC lsb. The extra bits are quite real.
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
That's correct, in any book.
Unfortunately, the digital world is full of techniques that claim to increase the level of accuracy.
It's all smoke and mirrors.
- Leigh
If you believe you can, or you believe you can't... you're right.
That's probably the most bizarre statement I've ever read.
- Leigh
If you believe you can, or you believe you can't... you're right.
It's not bizarre. The person I quoted stated that bits of resolution acquired through oversampling are not "real bits". I believe I understand his meaning perfectly; he means the oversampled bits are not "real" in that they don't add real accuracy or don't describe reality well. But he is wrong to make a blanket statement like that, because extra bits aquired through oversampling techniques can be just as accurate ("real") as those acquired from a hardware ADC. In fact you can create an ADC of arbitrary precision (ignoring bandwidth considerations) with only one bit of hardware resolution. So either the onnect17 is misinformed, or he has a different definition of "real" in mind when he says "oversampling cannot provide real extra bits".That's probably the most bizarre statement I've ever read.
Except any basic textbook on sampling theory or signals.That's correct, in any book.
There is plenty of smoke and mirrors to go around in both analog and digital techniques, but oversampling techniques are hardly smoke and mirrors, just basic sampling and signal theory. Yes, you really can get resolution below the resolution of an ADC via oversampling. I do it all the time, and the data aquired thusly is very "real". Consumer audio devices long ago went to 1-bit DACs run at ~MHz rather than 16-bit DACS run at 22kHz. Delta-sigma modulation (as used by the prized Super Audio CD format) can be called a 1-bit technique as it stores signals in 1-bit pulse frequency modulation, encoding a practically arbitrary amount of bit-depth with single-bit pulses. Is all the resolution of SACD "fake"? You can't say that oversampling is "smoke and mirrors" when the principles are in operation in millions or billions of electronic devices.
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
OK. I certainly agree with that statement.
Manufactured bits are not "real" bits, regardless of the method or technology used to create them.
I apparently misunderstood your previous post. My apologies.
- Leigh
If you believe you can, or you believe you can't... you're right.
What does it mean to "manufacture a bit"?
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
It means to create one or more bits by a technique unrelated to the basic conversion technique.
For example, you can create a bit by taking the average of two consecutive LSBs, and claiming that you have more resolution.
That's total nonsense, since the LSB is not significant in the first place.
- Leigh
If you believe you can, or you believe you can't... you're right.
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