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A newbie question about DSO oscilloscopes with CRT screens
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1
down vote
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To my ignorance I used to think all big CRT scopes were analogue oscilloscopes.
But I found out that there are digital storage oscilloscopes which were built by using CRT screens as well.
Below is an example:
I have two questions:
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
Why is there no FFT on such old scopes which are DSO with CRT screen?
oscilloscope
asked 2 hours ago
newage2000
13819
add a comment |Â
up vote
1
down vote
favorite
To my ignorance I used to think all big CRT scopes were analogue oscilloscopes.
But I found out that there are digital storage oscilloscopes which were built by using CRT screens as well.
Below is an example:
I have two questions:
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
Why is there no FFT on such old scopes which are DSO with CRT screen?
oscilloscope
asked 2 hours ago
newage2000
13819
This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago
add a comment |Â
up vote
1
down vote
favorite
up vote
1
down vote
favorite
To my ignorance I used to think all big CRT scopes were analogue oscilloscopes.
But I found out that there are digital storage oscilloscopes which were built by using CRT screens as well.
Below is an example:
I have two questions:
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
Why is there no FFT on such old scopes which are DSO with CRT screen?
oscilloscope
asked 2 hours ago
newage2000
13819
To my ignorance I used to think all big CRT scopes were analogue oscilloscopes.
But I found out that there are digital storage oscilloscopes which were built by using CRT screens as well.
Below is an example:
I have two questions:
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
Why is there no FFT on such old scopes which are DSO with CRT screen?
oscilloscope
oscilloscope
asked 2 hours ago
newage2000
13819
asked 2 hours ago
newage2000
13819
asked 2 hours ago
newage2000
13819
asked 2 hours ago
newage2000
13819
asked 2 hours ago
newage2000
13819
13819
This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago
add a comment |Â
This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago
This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago
This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago
add a comment |Â
3 Answers
3
active
oldest
votes
up vote
3
down vote
Not all scopes that can display digital information on their screens are DSOs.
A Digital Storage Oscilloscope, by definition, digitizes an analog signal, stores those digitized samples, and then displays it. DSOs could be constructed with LCDs, CRTs, or any other display technology--there are even DSOs that don't have any display at all, and rely on being connected to a PC to display captured data. So if there's no digitizing, and no storage, it's not a DSO.
It is this storage that provides the DSO the ability to perform arbitrary computations on the captured waveform, whether FFT, or integration, or whatever. But just displaying text on the CRT does not mean you have a DSO on your hands.
The sort of thing you see in the picture in the OP is actually not uncommon in analog 'scopes, especially later models. Essentially the CRT can be driven by the analog front end, where the horizontal position is controlled by a ramp generator (the horizontal timebase) and the vertical position is controlled by the channel amplifier, or it can be controlled by perhaps a small microprocessor to draw vector shapes, as you would see in a vector monitor. Essentially, the scope alternates between drawing waveforms and drawing informational text or other information on the screen, presumably doing the vector drawings in between triggers.
Some analog CRT scopes could even take digital measurements of voltage or time, with cursor position readouts and text menus that could be displayed and navigated through. However, it wasn't very long after that when DSOs became viable, and quickly took over the market.
answered 2 hours ago
ajb
1,418514
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
add a comment |Â
up vote
2
down vote
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
You're saying "CRT" when I think you actually mean "vector display".
Digital scopes had CRT's with bitmapped or raster displays were quite common from the first days of digital scopes until the price of LCDs dropped in the early 2000's.
These displayed text the same way any other CRT computer monitor did.
On a vector display, you can still display text. You just need a drawing routine that produces the text by routing the beam around the display and turning it on and off as required. You see this kind of text on things like radar displays going back probably to the 1950's or 1960's.
Why is there no FFT on such old scopes which are DSO with CRT screen?
An FFT takes a fair amount of processing power to perform quickly enough for the display to be responsive to user inputs. This was probably not possible with the microprocessors available at the price point the manufacturer and user wanted before maybe the mid-1990's.
answered 2 hours ago
The Photon
80k394189
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
add a comment |Â
up vote
0
down vote
You can just paint the text by steering the beam.
The X coordinate of the beam is not hardwired to a sawtooth, but also connected to a DAC, like the Y coordinate. The DACs read from sampling RAM, which contains ascending values for the X coordinate next to the sampled values, so the waveform is painted left-to-right. A microprocessor then writes a few extra positions at the end of the sampling RAM, which move the beam to the text area, and paint numbers.
E.g.:
0 0 on
1 4
2 6
3 7
4 6
5 4
6 0
7 -4
8 -6
...
999 -4 off
22 -200 on
21 -200
20 -200
20 -201
20 -202
21 -202
22 -202
22 -203
22 -204
21 -204
20 -204
The first 1000 positions in memory represent the sampled waveform, as X,Y pairs. Then, we turn off the beam, go back to the left, turn the beam back on and paint a 5 to the bottom of the screen.
FFT is a more complex operation that requires computing power, while simple sampling and reproduction of a waveform only require efficient streaming data paths to and from memory.
answered 2 hours ago
Simon Richter
6,24611026
add a comment |Â
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
Not all scopes that can display digital information on their screens are DSOs.
A Digital Storage Oscilloscope, by definition, digitizes an analog signal, stores those digitized samples, and then displays it. DSOs could be constructed with LCDs, CRTs, or any other display technology--there are even DSOs that don't have any display at all, and rely on being connected to a PC to display captured data. So if there's no digitizing, and no storage, it's not a DSO.
It is this storage that provides the DSO the ability to perform arbitrary computations on the captured waveform, whether FFT, or integration, or whatever. But just displaying text on the CRT does not mean you have a DSO on your hands.
The sort of thing you see in the picture in the OP is actually not uncommon in analog 'scopes, especially later models. Essentially the CRT can be driven by the analog front end, where the horizontal position is controlled by a ramp generator (the horizontal timebase) and the vertical position is controlled by the channel amplifier, or it can be controlled by perhaps a small microprocessor to draw vector shapes, as you would see in a vector monitor. Essentially, the scope alternates between drawing waveforms and drawing informational text or other information on the screen, presumably doing the vector drawings in between triggers.
Some analog CRT scopes could even take digital measurements of voltage or time, with cursor position readouts and text menus that could be displayed and navigated through. However, it wasn't very long after that when DSOs became viable, and quickly took over the market.
answered 2 hours ago
ajb
1,418514
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
add a comment |Â
up vote
3
down vote
Not all scopes that can display digital information on their screens are DSOs.
A Digital Storage Oscilloscope, by definition, digitizes an analog signal, stores those digitized samples, and then displays it. DSOs could be constructed with LCDs, CRTs, or any other display technology--there are even DSOs that don't have any display at all, and rely on being connected to a PC to display captured data. So if there's no digitizing, and no storage, it's not a DSO.
It is this storage that provides the DSO the ability to perform arbitrary computations on the captured waveform, whether FFT, or integration, or whatever. But just displaying text on the CRT does not mean you have a DSO on your hands.
The sort of thing you see in the picture in the OP is actually not uncommon in analog 'scopes, especially later models. Essentially the CRT can be driven by the analog front end, where the horizontal position is controlled by a ramp generator (the horizontal timebase) and the vertical position is controlled by the channel amplifier, or it can be controlled by perhaps a small microprocessor to draw vector shapes, as you would see in a vector monitor. Essentially, the scope alternates between drawing waveforms and drawing informational text or other information on the screen, presumably doing the vector drawings in between triggers.
Some analog CRT scopes could even take digital measurements of voltage or time, with cursor position readouts and text menus that could be displayed and navigated through. However, it wasn't very long after that when DSOs became viable, and quickly took over the market.
answered 2 hours ago
ajb
1,418514
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
add a comment |Â
up vote
3
down vote
up vote
3
down vote
Not all scopes that can display digital information on their screens are DSOs.
A Digital Storage Oscilloscope, by definition, digitizes an analog signal, stores those digitized samples, and then displays it. DSOs could be constructed with LCDs, CRTs, or any other display technology--there are even DSOs that don't have any display at all, and rely on being connected to a PC to display captured data. So if there's no digitizing, and no storage, it's not a DSO.
It is this storage that provides the DSO the ability to perform arbitrary computations on the captured waveform, whether FFT, or integration, or whatever. But just displaying text on the CRT does not mean you have a DSO on your hands.
The sort of thing you see in the picture in the OP is actually not uncommon in analog 'scopes, especially later models. Essentially the CRT can be driven by the analog front end, where the horizontal position is controlled by a ramp generator (the horizontal timebase) and the vertical position is controlled by the channel amplifier, or it can be controlled by perhaps a small microprocessor to draw vector shapes, as you would see in a vector monitor. Essentially, the scope alternates between drawing waveforms and drawing informational text or other information on the screen, presumably doing the vector drawings in between triggers.
Some analog CRT scopes could even take digital measurements of voltage or time, with cursor position readouts and text menus that could be displayed and navigated through. However, it wasn't very long after that when DSOs became viable, and quickly took over the market.
answered 2 hours ago
ajb
1,418514
Not all scopes that can display digital information on their screens are DSOs.
A Digital Storage Oscilloscope, by definition, digitizes an analog signal, stores those digitized samples, and then displays it. DSOs could be constructed with LCDs, CRTs, or any other display technology--there are even DSOs that don't have any display at all, and rely on being connected to a PC to display captured data. So if there's no digitizing, and no storage, it's not a DSO.
It is this storage that provides the DSO the ability to perform arbitrary computations on the captured waveform, whether FFT, or integration, or whatever. But just displaying text on the CRT does not mean you have a DSO on your hands.
The sort of thing you see in the picture in the OP is actually not uncommon in analog 'scopes, especially later models. Essentially the CRT can be driven by the analog front end, where the horizontal position is controlled by a ramp generator (the horizontal timebase) and the vertical position is controlled by the channel amplifier, or it can be controlled by perhaps a small microprocessor to draw vector shapes, as you would see in a vector monitor. Essentially, the scope alternates between drawing waveforms and drawing informational text or other information on the screen, presumably doing the vector drawings in between triggers.
Some analog CRT scopes could even take digital measurements of voltage or time, with cursor position readouts and text menus that could be displayed and navigated through. However, it wasn't very long after that when DSOs became viable, and quickly took over the market.
answered 2 hours ago
ajb
1,418514
answered 2 hours ago
ajb
1,418514
answered 2 hours ago
ajb
1,418514
answered 2 hours ago
ajb
1,418514
1,418514
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
add a comment |Â
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
Only one same beam is plotting both the waveform and the text on the CRT?
– newage2000
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
A dedicated DSP engine to drive the CRT display is all it takes. An LCD display saves weight, size and cost, but not so much in technology. It also needs a DSP engine to do FFT's and such. The faster the max sampling rate, the more money it cost.
– Sparky256
1 hour ago
1
1
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
@newage2000. It is easy to trick the eyes. They have data retention built in, about 1/20th second, so anything happening faster than that cannot be seen.
– Sparky256
1 hour ago
add a comment |Â
up vote
2
down vote
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
You're saying "CRT" when I think you actually mean "vector display".
Digital scopes had CRT's with bitmapped or raster displays were quite common from the first days of digital scopes until the price of LCDs dropped in the early 2000's.
These displayed text the same way any other CRT computer monitor did.
On a vector display, you can still display text. You just need a drawing routine that produces the text by routing the beam around the display and turning it on and off as required. You see this kind of text on things like radar displays going back probably to the 1950's or 1960's.
Why is there no FFT on such old scopes which are DSO with CRT screen?
An FFT takes a fair amount of processing power to perform quickly enough for the display to be responsive to user inputs. This was probably not possible with the microprocessors available at the price point the manufacturer and user wanted before maybe the mid-1990's.
answered 2 hours ago
The Photon
80k394189
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
add a comment |Â
up vote
2
down vote
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
You're saying "CRT" when I think you actually mean "vector display".
Digital scopes had CRT's with bitmapped or raster displays were quite common from the first days of digital scopes until the price of LCDs dropped in the early 2000's.
These displayed text the same way any other CRT computer monitor did.
On a vector display, you can still display text. You just need a drawing routine that produces the text by routing the beam around the display and turning it on and off as required. You see this kind of text on things like radar displays going back probably to the 1950's or 1960's.
Why is there no FFT on such old scopes which are DSO with CRT screen?
An FFT takes a fair amount of processing power to perform quickly enough for the display to be responsive to user inputs. This was probably not possible with the microprocessors available at the price point the manufacturer and user wanted before maybe the mid-1990's.
answered 2 hours ago
The Photon
80k394189
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
add a comment |Â
up vote
2
down vote
up vote
2
down vote
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
You're saying "CRT" when I think you actually mean "vector display".
Digital scopes had CRT's with bitmapped or raster displays were quite common from the first days of digital scopes until the price of LCDs dropped in the early 2000's.
These displayed text the same way any other CRT computer monitor did.
On a vector display, you can still display text. You just need a drawing routine that produces the text by routing the beam around the display and turning it on and off as required. You see this kind of text on things like radar displays going back probably to the 1950's or 1960's.
Why is there no FFT on such old scopes which are DSO with CRT screen?
An FFT takes a fair amount of processing power to perform quickly enough for the display to be responsive to user inputs. This was probably not possible with the microprocessors available at the price point the manufacturer and user wanted before maybe the mid-1990's.
answered 2 hours ago
The Photon
80k394189
How come a text like a number can be displayed on a CRT? I can understand how a signal leaves traces on a phosphor screen through electron beam hits on the CRT screen by deflecting rays. But how is a text displayed?
You're saying "CRT" when I think you actually mean "vector display".
Digital scopes had CRT's with bitmapped or raster displays were quite common from the first days of digital scopes until the price of LCDs dropped in the early 2000's.
These displayed text the same way any other CRT computer monitor did.
On a vector display, you can still display text. You just need a drawing routine that produces the text by routing the beam around the display and turning it on and off as required. You see this kind of text on things like radar displays going back probably to the 1950's or 1960's.
Why is there no FFT on such old scopes which are DSO with CRT screen?
An FFT takes a fair amount of processing power to perform quickly enough for the display to be responsive to user inputs. This was probably not possible with the microprocessors available at the price point the manufacturer and user wanted before maybe the mid-1990's.
answered 2 hours ago
The Photon
80k394189
answered 2 hours ago
The Photon
80k394189
answered 2 hours ago
The Photon
80k394189
answered 2 hours ago
The Photon
80k394189
80k394189
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
add a comment |Â
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
Is it the same single beam drawing both the waveform and the text? Is the signal digitized processed and converted back to analog waveform before deflecting the beam on the vector display?
– newage2000
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
@newage2000, AFAIK, the answer to both your questions is yes. But the amount of "processing" in that era was probably very minimal. In spectrum analyzers with similar technology, you might see things like peak hold, averaging, or adding or subtracting two traces, but not much more.
– The Photon
1 hour ago
add a comment |Â
up vote
0
down vote
You can just paint the text by steering the beam.
The X coordinate of the beam is not hardwired to a sawtooth, but also connected to a DAC, like the Y coordinate. The DACs read from sampling RAM, which contains ascending values for the X coordinate next to the sampled values, so the waveform is painted left-to-right. A microprocessor then writes a few extra positions at the end of the sampling RAM, which move the beam to the text area, and paint numbers.
E.g.:
0 0 on
1 4
2 6
3 7
4 6
5 4
6 0
7 -4
8 -6
...
999 -4 off
22 -200 on
21 -200
20 -200
20 -201
20 -202
21 -202
22 -202
22 -203
22 -204
21 -204
20 -204
The first 1000 positions in memory represent the sampled waveform, as X,Y pairs. Then, we turn off the beam, go back to the left, turn the beam back on and paint a 5 to the bottom of the screen.
FFT is a more complex operation that requires computing power, while simple sampling and reproduction of a waveform only require efficient streaming data paths to and from memory.
answered 2 hours ago
Simon Richter
6,24611026
add a comment |Â
up vote
0
down vote
You can just paint the text by steering the beam.
The X coordinate of the beam is not hardwired to a sawtooth, but also connected to a DAC, like the Y coordinate. The DACs read from sampling RAM, which contains ascending values for the X coordinate next to the sampled values, so the waveform is painted left-to-right. A microprocessor then writes a few extra positions at the end of the sampling RAM, which move the beam to the text area, and paint numbers.
E.g.:
0 0 on
1 4
2 6
3 7
4 6
5 4
6 0
7 -4
8 -6
...
999 -4 off
22 -200 on
21 -200
20 -200
20 -201
20 -202
21 -202
22 -202
22 -203
22 -204
21 -204
20 -204
The first 1000 positions in memory represent the sampled waveform, as X,Y pairs. Then, we turn off the beam, go back to the left, turn the beam back on and paint a 5 to the bottom of the screen.
FFT is a more complex operation that requires computing power, while simple sampling and reproduction of a waveform only require efficient streaming data paths to and from memory.
answered 2 hours ago
Simon Richter
6,24611026
add a comment |Â
up vote
0
down vote
up vote
0
down vote
You can just paint the text by steering the beam.
The X coordinate of the beam is not hardwired to a sawtooth, but also connected to a DAC, like the Y coordinate. The DACs read from sampling RAM, which contains ascending values for the X coordinate next to the sampled values, so the waveform is painted left-to-right. A microprocessor then writes a few extra positions at the end of the sampling RAM, which move the beam to the text area, and paint numbers.
E.g.:
0 0 on
1 4
2 6
3 7
4 6
5 4
6 0
7 -4
8 -6
...
999 -4 off
22 -200 on
21 -200
20 -200
20 -201
20 -202
21 -202
22 -202
22 -203
22 -204
21 -204
20 -204
The first 1000 positions in memory represent the sampled waveform, as X,Y pairs. Then, we turn off the beam, go back to the left, turn the beam back on and paint a 5 to the bottom of the screen.
FFT is a more complex operation that requires computing power, while simple sampling and reproduction of a waveform only require efficient streaming data paths to and from memory.
answered 2 hours ago
Simon Richter
6,24611026
You can just paint the text by steering the beam.
The X coordinate of the beam is not hardwired to a sawtooth, but also connected to a DAC, like the Y coordinate. The DACs read from sampling RAM, which contains ascending values for the X coordinate next to the sampled values, so the waveform is painted left-to-right. A microprocessor then writes a few extra positions at the end of the sampling RAM, which move the beam to the text area, and paint numbers.
E.g.:
0 0 on
1 4
2 6
3 7
4 6
5 4
6 0
7 -4
8 -6
...
999 -4 off
22 -200 on
21 -200
20 -200
20 -201
20 -202
21 -202
22 -202
22 -203
22 -204
21 -204
20 -204
The first 1000 positions in memory represent the sampled waveform, as X,Y pairs. Then, we turn off the beam, go back to the left, turn the beam back on and paint a 5 to the bottom of the screen.
FFT is a more complex operation that requires computing power, while simple sampling and reproduction of a waveform only require efficient streaming data paths to and from memory.
answered 2 hours ago
Simon Richter
6,24611026
answered 2 hours ago
Simon Richter
6,24611026
answered 2 hours ago
Simon Richter
6,24611026
answered 2 hours ago
Simon Richter
6,24611026
6,24611026
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This is analog scope with vector text display only.
– Tony EE rocketscientist
1 hour ago