Why is China not a high-end oscilloscope
Some things cannot be continuously studied in depth. Only the continuous demand of the market continues to stimulate technological progress. Just like war, technology can make a huge leap. In addition, advances in some other technologies, such as electronic computers, have also been complemented by the development of instruments, which has also brought about a comprehensive improvement in thinking.
As the most basic comprehensive instrument in the electrical measurement industry, the oscilloscope is also involved in the design and manufacture of a wide range of fields, from semiconductors to specialty materials, from machining to electronic design. This requires a strong and complete industrial system as a support. But did the Soviet Union have all this in the early days? Why did the Soviet Union not do it? In fact, the market is also very crucial. Only relying on the state power, it may be able to focus on solving problems in a short period of time and then invest in other problems. Some things cannot be continuously studied in depth. Only the continuous demand of the market continues to stimulate technological progress. Just like war, technology can make a huge leap. In addition, advances in some other technologies, such as electronic computers, have also been complemented by the development of instruments, which has also brought about a comprehensive improvement in thinking.
Involved in the specific technology related to oscilloscopes, from the 1960s, generally speaking, the gap between China and foreign countries is not particularly large, because everyone uses electronic tubes, this thing has nothing to do with industrial machinery and equipment, mainly stamping and welding, etc. Etc. In addition, the special cathode coating material of the tube is also critical to the performance, but this is not out of reach. In addition, the oscilloscope bandwidth of this period usually does not exceed 40MHz. The difficulty is not particularly large. At this stage, we have not much difference with the technical reserve, mainly because the demand is not too much, resulting in some products falling behind in terms of process and structure. .
Part of the oscilloscope, you can see that there are many text prompts printed on the backplane, which is more elaborate.
By the way, the manufacturing process of this era, because the tube itself is large, and most of the devices with high voltage and high current, the size of the device used is very large, both domestic and foreign are installed components, that is, the components are installed in On the brackets, then connect them to each other with wires. This method is commonly known as scaffolding in China.
In the mid-1960s, some semiconductor devices began to gradually replace the position of the tube, and the bandwidth of the oscilloscope began to reach 100MHz. In this period, the application of electronic computers began to gradually spread, which led to more demand for oscilloscopes. At this time (circa 1965), HP also released the HP-IB bus, which was later standardized as IEEE488 or GPIB in the 1970s. Through this control bus, the computer can control the operation of the electronic instrument, collect the data of the instrument and analyze it. This has brought us to a new level of use and understanding of data, and at the same time gave birth to the concept of automated measurement systems, which brought greater efficiency and better accuracy. At this time, there is still not much progress in China. High-bandwidth oscilloscopes place very high demands on processing technology and design, and electronic computers are not much in the country.
As transistors shrink in size and power consumption, printed circuit board technology is beginning to be promoted, and electronic components can be quickly and orderly mounted through PCB boards while reducing parasitic parameters. Therefore, the manufacturing technology of the circuit board has also followed up development.
This video was taken in 1969 by Tektronix about the entire process from PCB design to production. You can see how it was done at the time. It can be suggested that the elegant curves of the above picture are all drawn manually.
The picture comes from an old predecessor DIY, but at that time the domestic PCB was basically like this. It looks a lot more rough. The main method is to punch and rivet the mounting points of each component, and then solder them on the rivets, and the opposite sides are connected to each other. Such a process is inefficient and has a low installation density. These auxiliary industries also seriously affect the integration of the instrument.
In the 1970s, our catastrophe continued. The microwave semiconductor technology of the United States is advancing by leaps and bounds, and the microelectronic integrated circuit technology is changing with each passing day. The bandwidth of the conventional oscilloscope reaches 350MHz during this period, and the special oscilloscope can reach 1GHz. At the same time, the further development of semiconductor technology makes the oscilloscope fully programmable, and digital acquisition is also possible. For example, the analog oscilloscope of the same era already has a microprocessor, which can intuitively read the measurement parameters on the screen, and can transfer the parameters and waveforms to the computer. It was not until decades later that domestic analog oscilloscopes began to have this capability. At this time, our semiconductor industry has stopped and can only produce ordinary logic gate circuits. Of course, the CPU of the 8086 class is also copied, but think about it, 1 no one will use it, 2 cost is scary, 3 use these things to do measuring instruments, greatly increase the cost and complexity of the instrument, but not enough The computer is matched with it. At this time, the measurement demand mainly depends on the import (the Sino-US relationship is still okay). In this era, due to the needs of the instrument and the military, the United States began to make 4-layer boards and used early computers for EDA-assisted circuit design.
For example... no more than really don’t know how big the gap is.
The 1980s was the era when PCs and bullies took off. In this era, thanks to the demand for ultra-large-scale circuits in many industries, oscilloscopes have followed the light and entered the digital age. Due to special requirements such as radar, GaAs semiconductor technology has grown rapidly and is used in RF measuring instruments such as network analyzers and spectrum analyzers. These other areas of technology have paved the way for high-performance digital oscilloscopes. However, due to the scarcity of related industries in China, there has been a huge technical fault at this time, and it has not been able to catch up until today. If you are interested, you can look at the various American bullies of the 80s, useful for a variety of CPUs, such as Z80, MC6800, MC68000, 6502, and so on. It has to be said that the market has played a huge role. Due to the manufacture of these consumer electronic products, there is also a huge demand for electrical measuring instruments. During this period, the extremely high density of components also promoted the maturity of SMD surface mount technology, which represents the integration of the circuit, stability, and production speed.
In the early 1990s, with the increasing complexity of computers and various network systems, higher requirements were imposed on measuring instruments. At this time, the high-performance digital oscilloscope represented by the HP54600 series and the Tektronix TDS500 series was introduced. After a long period of technical accumulation, the digital oscilloscope at this time incorporates advanced semiconductor technologies such as microcomputers, DSPs, CPLDs, and specially designed ASICs and ADCs that represent core technologies, trigger controllers, and so on. In terms of software, it is also a collection of advanced measurement algorithms. It can be said that no matter which way, in that era, our gap is not a little bit. After all, the parts that make a 286 can't be completely localized. What about more advanced oscilloscopes?
Therefore, the question of the subject is actually very broad in my opinion. He involves many fields. Although it may be limited to a few key devices from the perspective of an instrument itself, it is a long-term solution to make these things by not organizing several national technical breakthroughs. The product of accumulation and progress is also the crystallization of wisdom. It is also the inevitable result of adapting to the development of the times and market demand.
In the following, a more in-depth understanding of the concept of technology accumulation by simply looking at the history of the oscilloscope. Also, look at the brain holes of the predecessors.
Ancient times (before the 90s). HP has not been split, so he also produces electrical instruments, and he is made up of instruments. After the split, the electrical and biochemical measurements are called agilent (now the electrical test is split again called keysight). The semiconductor technology is called avago. Similarly, Tektronix used MAXTEK to design and manufacture special custom parts for the company's instruments.
01: Prehistoric times
The starting point of an electronic oscilloscope is not easy to verify, so the prehistoric era is divided by the operating characteristics of the oscilloscope. The most common feature we use today is the edge-triggered mode, which is often thought of as part of the basic functionality of an oscilloscope. In fact, before the TEK 511, the oscilloscope did not have the ability to trigger. In order to stably display the waveform, the oscilloscope at this time uses a technique called synchronous scanning. The oscilloscope scans freely at a fixed frequency to display the waveform. To stabilize the waveform, he also has simple comparator control to determine when to start scanning. However, due to the uncertainty of the scanning time, the time axis of the oscilloscope is also unstable. Such an oscilloscope cannot perform accurate time measurements or observe aperiodic signals.
In 1947, Tektronix released his first product: the 511 oscilloscope.
The biggest difference with his predecessors is that he has the precise triggering system for the first time, which is actually the edge level trigger that every oscilloscope we can see today. When the input waveform meets the polarity and threshold set by the trigger comparator, the oscilloscope begins a scan at the time set by the time base knob. In this way, the starting level of each scan on the waveform can be determined by adjusting the trigger level, and the time of each scan is known. The time-domain analysis of the measured signal can be performed by the grid on the screen. This is a huge leap, and the simple principle has become a necessary function for every oscilloscope today. It must be said that he is the starting point of modern oscilloscopes.
01: Solid state, miniaturization
In the 1960s, when RF semiconductor technology advanced by leaps and bounds, companies such as HP and TEK urgently needed high-performance solid-state amplifiers and replacement devices for various tubes. Since general-purpose devices companies could not provide these components, they set up their own R&D departments to meet domestic demand. . Since the military also has huge demand, the most important funds are naturally not a problem. In the case of an oscilloscope, to make the bandwidth high, an oscilloscope with higher brightness, more precise focusing, and faster slew rate is required, as well as a high-speed preamplifier/Y-axis amplifier. Since the 1960s, other tubes besides the oscilloscope have been replaced by transistors and integrated circuits.
The Tektronix 555 oscilloscope, which was launched in late 1959, has a bandwidth of 30MHz and is manufactured using a complete tube structure. The power consumption and volume are huge. The bottom layer of the trolley is his power box..... obviously such an oscilloscope seems too So huge that leaving his car is simply impossible to use.
In the early 1960s, as the mass production of transistors was gradually solved, the process of solid state of the instrument began. At this time, Tektronix introduced the Model 321 oscilloscope. He used almost all of the transistors, and some of the tubes in the early models worked in high-voltage areas, and later models replaced them with new transistors. The oscilloscope at this stage is reduced and the weight is reduced. It can finally be taken off the cart, placed on the table, or easily moved to some special measurement site.
Huge market demand spurred them to develop all the accessories they needed, and led to other industrial projects, such as precision machining equipment for glass and metal stamping equipment. In the late 1960s, the American enamel had been able to manufacture precision internal oscilloscopes. That is, the grid on the screen of the waveguide is engraved on the glass surface inside the oscillating tube. This makes the reading error smaller. In the same era, domestic oscilloscopes were all engraved on the acrylic sheet and placed on the front of the screen. There were different errors from different angles. Coupled with no actual demand, it was not until the late 1980s that a small portion of the inner oscillating oscilloscope was produced, mainly for ultrasonic flaw detectors.
The two oscilloscope tubes I have are from the TEK 212 and 2430 oscilloscopes. The two tubes are about 70-80s. They have detailed inner scribe lines and can be clearly seen when there is light (on the oscilloscope). There is a tungsten light bulb backlight).
A very small TEK 212 handheld analog oscilloscope, about the product of the early 1980s, mainly supplies military demand. The bandwidth is 0.5MHz.
The precise and beautiful accelerating electrodes in the oscilloscope tube allow the electron beam to carry a relatively high amount of energy, so that the oscilloscope can still have sufficient brightness for observation at high sweep speeds.
Ok, it’s a bit far. Come back
02: High integration and modularity, automation, data analysis
When the integrated circuit enters the oscilloscope, I did turn a lot of information and it is difficult to determine.
However, our company once had a Tektronix 485 left by the old predecessor. He was born in 1972. The company was produced around 1978. His bandwidth is 350MHz, which was a realm of domestic goods at that time. And the interior is very complicated and the manufacturing process is quite sophisticated. Unfortunately, one day when I was playing with him, suddenly it was black and the fan stopped spinning. Suspected that there is a problem with the switching power supply (yes, in 1972, the switching power supply was used). Then the site was dismantled for maintenance, and it was too complicated to find it. The whole machine was wrapped in PCB inside and outside, the power supply was in the center... So I took some photos and put them back. Return to the warehouse to sleep. Ok, no more nonsense, above:
Still able to boot photos
Beautiful panel, with some buttons for backlighting or tungsten bulbs.
At the rear of the machine port, it can be seen that there have been active probes during this period: he has two active probe power supply interfaces.
Remove the screws on the back and pull out the case. All the densely packed boards
Product inspection signature on the oscilloscope.
A unique integrated circuit that TEK customized at the time.
There are a lot of...
The input channel section is also very complicated.
The individual integrated circuits I received in my spare time, the strange one in the middle is TEK's own custom products. These things are very good for our technical staff at the time, and it is difficult to guess his specific use. The further emergence of integrated circuits and microprocessors has opened up a good way for the automation of oscilloscopes. As the boss of Tektronix, naturally, this opportunity will not be missed.
In the mid-1970s, all aspects were met and the time was ripe. Tektronix introduced the 7000 Series Modular Oscilloscope. A host of display units installed various modules to define various functions of the instrument.
And it has a variety of modules...
You can see it here, it is too much. For example, the horizontal and vertical modules required by the oscilloscope, the TDR module that crosses the frequency domain and the time domain, the frequency meter required for the radio frequency, and the spectrum analyzer module. The logic analyzer module required for digital circuit verification at the time...
Of course, no matter how he changed his magic, he still simulated the oscilloscope. Analog oscilloscopes have many inconveniences, such as low bandwidth and inability to store. In the 1970s, when high-speed digital-to-analog converters were not developed, high-energy physics experiments and microwave and radar system measurements urgently required high-bandwidth, analog oscilloscopes that could be stored. So there are some real black technology products (absolutely different from those of a certain rice promotion). Let's talk about bandwidth, the conventional analog oscilloscope, that is, the kind of screen that looks at the screen with the human eye. The highest record holder is the product of Japan Iwasaki (should also be in the late 80s) (the model I really don't remember), his bandwidth is up to 470MHz! In the 1980s, Tektronix products could only reach 400MHz (2467B). Because the oscilloscope tube of the ordinary desktop oscilloscope has a large display area, the electron beam stroke is long, and the Y-axis driving capability cannot be increased indefinitely, thereby limiting the overall bandwidth of the oscilloscope, so some oscilloscope tubes can reach a bandwidth of 600 MHz. But the driver circuit is difficult to achieve such a level.
Let's talk about storage. Everyone knows that if an analog oscilloscope uses a single trigger, the waveform sweeps away from the screen, and after a few ms of afterglow, it will disappear forever. So technology has two directions, one is an oscilloscope camera. This dedicated camera is mounted on the oscilloscope screen and keeps the shutter open all the time. After the oscilloscope triggers, the shutter is closed and an exposure is completed. This is a clever approach, but every time you want to see the recorded waveform you need to rinse the film.
Two oscilloscopes with dedicated cameras, look a bit strange
Some adjustment options on the side of the camera, such as focus, aperture, shutter speed, film speed, etc.
TEK's 1973 booklet on the use of oscilloscope cameras.
Because of the cumbersome use of the oscilloscope camera, there is another technology, namely the memory oscilloscope. The oscilloscope has a special storage grid mounted behind the screen and a dedicated readout gun inside the oscilloscope. After the main electron gun completes a scan, an electronic gap is left on the gate. Then, the read-out electron gun is turned on, and the electron-emitting screen is uniformly emitted to the storage gate. One part is blocked by the storage gate, and the other part is irradiated onto the screen through the gate, and the stored waveform is reproduced.
To store the schematic diagram of the oscilloscope, it can be seen that he has two more FLOOD GUNS and a set of gates placed behind the screen. However, this oscilloscope can only be stored for a few minutes and then blurred due to electronic leakage. The representative model of the later stage is HP Model 1741A. This special tube is also used in radar displays and RAM memory in early computers. This kind of oscilloscope tube requires more precise mechanical structure, and the tube with low bandwidth can be successfully produced in China.
My 1741A oscilloscope
At this point, the oscilloscope is not connected to the probe, and the waveform just stored is displayed on the screen.
After a few minutes, the waveform begins to blur and eventually turns into a green screen.
The 1741A oscilloscope tube, at this angle, can be seen with a readout electron gun with a white ceramic back cover.
This demonstrates the low-speed scanning process in the storage mode, first full-screen green light, which is the "erase" of the oscilloscope, followed by a scan, the waveform still does not disappear after the first scan.
In China, the SC-7 storage tube produced in 1973, he replaced the phosphor with an electronic target for recording and reading data.
By the mid-1970s, computers were also miniaturized, and they were used more in the field of measurement control and analysis. This requires an electronic instrument to record his measurements and digitize them. This seems to be a problem for oscilloscopes, because at the time it was not possible to produce high-bandwidth, high-sampling ADCs. At this time, the United States has mobilized its brains. This time, Tektronix developed the Model 7912 (circa 1973) Digitizer.
The advertising brochure for this type of device focuses on his ability to connect to a computer.
He still uses an analog oscilloscope with a bandwidth of up to 1 GHz, which is about 2 Gsa if it is equivalent to the sampling rate of a digital oscilloscope. It also provides a digital waveform output with a dynamic range of approximately 12 bits. How did he do it? Tektronix used the Scan conversation tube. This is a wonderful oscilloscope with two heads, one for the oscilloscope and the other for waveform scanning. Camera tube for image recording (the product before CCD has not been used in large quantities). The center of the two tubes is the recording target. The oscilloscope emits a scanning electron beam to the recording target, and then is output by the camera tube and the low-speed AD converter to complete recording of the high-speed signal.
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