DE3302548A1 - ULTRASONIC MISTAKE DETECTOR SIGNAL ANALYZER - Google Patents

Description

The invention relates to an analyzer for the treatment and analysis of the electrical signals transmitted by an ultrasonic flaw detector can be generated, which is used in non-destructive testing of materials, especially for checking turbine disks of gas turbine engines .

Internal defects in workpieces that are essentially based on weakening of the material structure of such workpieces, are formed during the treatment of the raw material, during the production of the workpiece and also during operation. The uncovering Such imperfections are essential, especially in the case of highly stressed components such as turbine disks. If the The location and size of the imperfections is known, then by applying modern methods through fracture mechanics with considerable Accuracy the expected service life of the workpiece can be determined.

A common method of nondestructive testing of turbine disks for internal imperfections is to immerse the disc in a water bath and then turn it and thereby exposing ultrasound pulses emitted by an ultrasound probe that move slowly across the disc is moved away. Each pulse is reflected by the workpiece in a sequence of echoes, with echoes from on the one hand the front and, on the other hand, echoes originate from the rear of the workpiece. In addition, there are echoes with changing Size which are referred to as "grit" (grass) and in the following also referred to as "noise" or "interfering signals" will. They arise from the grain structure of the material of the workpiece and when the pulse is emitted over the flaw there is an echo corresponding to the defect. The size of the defect has a certain relationship the size of the corresponding echo. When the pulse is emitted in the area of a change in cross-section of the workpiece then there are further echoes, which are referred to as "geometry echoes".

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All of these echoes are displayed on a screen and the operator must identify an echo which is above the current noise level when the defect passes under the probe and disappears again. The most critical case is when a flaw is in the area of a jump in cross section and the flaw | echo is masked by the geometry echo, for example; f defects echo instantly on the trailing edge of the ^rela-: {tively large geometry echo signal occur. The visual festival; Positioning such a defect requires considerable concentration over long periods of time and, in addition, a great deal of experience and knowledge of the pattern to be expected is required. Even a momentary decrease in concentration can result in a defect running through it undetected. ;

The invention is based on the object of creating an arrangement by means of which it is possible to handle the signals and analyze resulting from the echoes reflected from the workpiece, that of a non-destructive one Is subjected to ultrasonic material testing in such a way that that a defect echo size and location, especially in loading; shown and recorded when there is a change in cross-section ί without the need to continuously visually observe the echo signals.

The invention is based on a signal analyzer, the meh- _; rere signal processing channels and in this case the object is achieved in that each channel receives the signals to be analyzed via a gate, that the gates can be actuated by a blanking control in order to transfer the signals to be analyzed for each channel one after the other to the signal processing channels, that each channel has a hold circuit which receives the peak value of the signal in the corresponding time blanking interval and holds that

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an average filter receives the output of the hold circuit, that a first comparator receives the outputs from the hold circuit and the average filter, the Output of the first comparator is fed to a second comparator which also receives a threshold value signal and that the output of the second comparator is used to determine whether the signal from the first comparator is meaningful is or not and if it is meaningful the output of the first comparator is recorded.

The output of the second comparator can be an analog-to-digital converter which enables the output of the first comparator to convert it into digital form, when the output of the first comparator is greater than a predetermined threshold value. The converted data can be fed to a data line via a buffer with three states, the data line being connected to a first first-in, First-out memory (FIFO memory) is connected, from which the data is a visual display and a printer and / or can be fed to a computer for the purpose of data analysis.

The signal analyzer can be used in particular to process the echo signals to analyze by an ultrasonic flaw detector can be generated in which regular pulses of ultrasonic energy are directed at a workpiece for testing purposes will. The input to the analyzer includes the echo signals from the workpiece, and these signals are preferred treated by a variable attenuation stage and a logarithmic amplifier before the signals in signal treatment channels are fed via the gates.

The gates can have clock circuits with adjustable cycle times have to deliver blanking pulses of selected width. A shift register is also provided. The clock circuit is activated by an impulse sent by the

position detector is emitted via a delay stage or directly through the front wall echo signal de ;; workpiece to be tested. The clock circuit can blanket pulses of uniform width the width of which can be changed by the operator or the blanking pulses of a second clock, whereby the width of the blanking pulses can be made dependent on the strength of the echo signal so that the geometry echoes can cause the width of the blanking pulses to be reduced so that the Geometry echoes are made more clearly recognizable.

The output of the first comparator represents the signal in decibels (dB) above the noise level and when the signal is above the Then the second comparator recognizes the signal as a fault signal and causes the A / D converter to operate converts the signal into digital form. The vacancy size data are formed together with the vacancy depth a number of pulses from the uniform clock to the FIFO memory and also to the visual Representation and the printer and / or a computer. The visual representation and the printer and / or computer received also data indicating the total number of voids found and the printer and / or the Computers receive data from a mechanical scanning system that indicates the location of the flaw.

Each signal treatment channel can be analog or digital devices have and in analog form, the first and second comparators have a differential amplifier and a Analog comparator and the memory circuit comprises a capacitive circuit which comprises a capacitor and a buffer.

In digital form, both comparators are of digital design and the memory circuit comprises a digital register and a

The only analog-to-digital converter replaces the converters in the signal processing channels and is arranged so that the input signal of the defect detector is converted before it passes through each treatment channel.

Exemplary embodiments of the invention are illustrated below described in the drawing. In the drawing show:

Fig. 1 is a typical echo diagram showing the echo signal amplitude shows as a function of time

2 shows, on a larger scale, part of the echo diagram on a change in cross-section of the workpiece without Presence of a defect signal

3 shows a diagram corresponding to FIG. 2, but with a fault signal being present

Fig. 4 is a block diagram of an embodiment of the signal analyzer according to the invention

FIG. 5 shows a block diagram of one of the analog signal treatment channels of the analyzer according to FIG. 4

Figure 6 shows signal waveforms at various stages along the channel of Figure 5

7 shows a schematic representation of the analyzer according to FIG. 4 coupled with a defect detector and a non-destructive testing system

FIG. 8 shows a block diagram of a digital embodiment of the signal treatment channel according to FIG. 5.

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Figure 1 shows a diagram of the echo signals from an i

Workpiece can be obtained, which has a change in cross-section ί

having. The signals A and B are the echo signals transmitted by |

the front wall or the rear wall of the workpiece received ί

and the signal C is the signal, the cross-section change- f

tion, which · is referred to as a "geometry echo" and it is ί

furthermore a signal D is present, which the background echoes |

represented by the grain structure of the workpiece, which is referred to as "noise" I.

Figure shows the trailing edge of the sequence relatively on a larger scale large damped oscillations of the "geometry echo" C. In known methods for localizing flaws it is required that the operator recognizes the defect as a separate signal that suddenly occurs on this vibration pulse train occurs according to Figure 3. The signal analyzer according to the invention proposes to use the geometry echo signal to test a sequence of gates of variable time width. Figures 2 and 3 together show the effect of using different Gate pulse widths.

In FIG. 2 the peak signal is in a wide gate pulse the duration t is shown as an oscillation of the geometry echo. In Figure 3, the peak signal at a gate is the same duration as in Figure 2 because, although a flaw signal E occurred during the gate transit time is, this is smaller than the neighboring part of the Geometry echoes.

FIG. 2 also shows the mode of operation with a narrow gate pulse of duration t ₂ and the peak signal within this gate is the next lower cycle of the geometry echo. In FIG. 3, the flaw echo Γ rises within the same narrow gate above the value in the narrow gate according to FIG

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Figure 2 and provided that the voids echo exceeds a predetermined threshold level which is the same level above the noise level, the defect becomes recognized and recorded.

As will be described in detail below, the analyzer narrow gate pulses with a duration of about 100 ns in the area of the geometry echo and wider gate pulses otherwise use. The operator can choose to use one of two clock generators to set the gate pulse width to control. A uniform clock or one by echo size controlled clock which generates pulses of a predetermined period unless a substantial echo is received, e.g. a geometry echo is then received. The instantaneous size of the received signal determines the instantaneous ! Duration of the clock pulses and accordingly the gate pulses or the

j blanking pulses that are narrower if echoes with larger

j amplitude occur.

'■ Figure 4 shows in block form the main components of the analysis

tors and recording and reproducing devices, the Analyzer is switched to the simplest operating mode. The main part of the analyzer is carried out by a group of Si

gnalbehandlungskanäle 10 formed, which the echo signals from

\ received the workpiece that has just been tested. The channels will

controlled by a shift register 12, which the blanking pulses and generated by an adjustable clock generator 14 with a uniform pulse width which has a logic "1" signal through the register, the clock being triggered by the top surface of the echo signal of the workpiece. The T, ogisch "1" output signal opens the gate of each PC channels one after the other.

distinct data from the channels 10, i.e. the data that indicate the presence and size of a defect are detected by a data detector circuit 16 and

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causes the data to be sent to a First In First Out (FIFO) memory 18 are fed. At the same time, the data detector circuit causes that the output from a depth counter 20 indicates the depth of each crack or flaw, as a number of time slots from the output of the clock generator 14 in order to input these into the FIFO memory 18.

The data detector stage 16 also sends scanning coordinates into an independent FIFO memory 22. The scanning coordinates are supplied by position transducers which are in the component scanning system are built in. These coordinates are usually binary numbers or binary coded decimal numbers (BCD numbers). If the workpiece is a turbine disk these numbers represent the current position of the ultrasound probe relative to the disk as a distance from the center point (radius) and rotation from a reference mark (angle). The data detector circuit 16 loads not only the FIFO memory, but also transfers a pulse to a flaw counter 26.

The data are transferred from the FIFO memory 18 via data lines 28 and 39 to a display device 32 and a printer 24 and / or a computer 34 which also receives data from the defect counter 26 via a data line 36. The printer and / or the computer also receives data from the FIFO memory 22 via a data line 37. The complete group of data of each defect includes information about the size in dB, about the depth as number of time pulses, about the radius in mm or inches and the angle in degrees and this data is used together with the total defect count by the Printer 24 prints out at a rate of about 1 line per second. When the time for showing up If a different speed is set then the system allows the printer to run on its own Speed can work regardless of the representation.

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The FIFO memory 18 is used as a temporary memory, in order to adapt to a possible rapid acquisition of the local area of the disk with regard to the relative to achieve the low speed required for display and recording. The capacity of the memory is adapted to the likely number of imperfections and in the case of a turbine disk, the memory has j such a capacity that sixteen voids are stored

j, because only one or two missing spots in the bad j the most likely cases are to be expected. So-

] soon entered the flaw data into the FIFO memory

are, they appear on the display 32 during a

Time determined by a presentation timing. At the end of this time, the next group of data will be the FI-. FO memory shown usv /. If the group leads of voids to a rapid succession of voids data from the signal processing channels 10, the groups of data are temporarily stored in the FIFO memory and retrieved for display with a suitable rate of the operating ^is determined ⁱⁿ person. If the FIFO memory is temporarily

'. should be full or if the operator

: place measured on the display screen 30, then the genre can

: total number of defects found due to the defect

j The count reading can be seen on the screen.

The screen display does not show any sampling coordinates because

these are usually represented by the disk scanning system ! but they are recorded in printer 24 and / or computer 34

• drawn.

Reference is made to FIGS. 5, 6 and 7 below. Each signal handling channel 10 includes a gate 38, one pointed key memory 40 with a capacitor and an amplifier with unity gain, an average value filter, a differential amplifier 44, a comparator 46,

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an analog-to-digital converter 48 and a three-state buffer circuit 50, the output of which is connected to a data line is that with the data detector stage 16 and the FIFO memory 18 communicates.

The signal treatment channels 13 are arranged parallel to one another and receive sequentially treated echo signals from the workpiece. The echo signals are first passed through an amplifier 54 attenuated or amplified with a variable gain that adjusts the level of the signals so that it is suitable for a logarithmic amplifier 56 has the appropriate value. The output voltage of amplifier 56 represents the logarithm its input voltage and accordingly it represents the input voltage in decibels. The gates 3 will be 8 of the channels opened one after the other, so that each gate is consecutive Can inspect parts of the echo signal. The gates are controlled by the shift register 12, which in turn by a changeable timer 14 or by a through one Echo size controlled timer 58 is controlled. The timer circuits 14 and 58 have switches to each clock input control and operate the shift register 12. The clock 14, however, continues to work around the 'depth counter 20 to operate when the clock 58 is in use.

Both clock generators can get through the front wall echo via the interface trigger circuit 59 can be triggered. Instead, both clock generators can be triggered by the transmission pulse after a delay which is set by the delay stage 60.

The blanking signal for a special gate, which is from the shift register is fed, also serves to clear the analog-to-digital converter of that gate and the blanking signal from the previous gate is used to clear the peak keypad 40 and the n three-state buffer 50 to

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set. The analyzer receives signals from the defect detector 62, which can also be assigned an oscilloscope 64 and of a position indicator, not shown, which indicates the location of the probe 66 relative to the workpiece 68 that is immersed in the water tank 70.

Each gate 3 8 releases the associated signal processing channel 10 in order to receive the ultrasonic echo signal from a thin horizontal Evaluate section of the turbine disk to be checked. The waveform (i). represents the ultrasound image of the defect detector repeating a few times to show the result of changes in the received echoes, when the disc turns. The time base is compressed for the sake of simplicity.

Waveform (ii) is the blanking pulse waveform shown.

Waveform (iii) shows only one of the blanking pulses, that which the gate in each of the shown in FIG Channels opens.

Waveform (iv) shows the voltage across the capacitor of the tip key memory circuit 40 and it represents the output of the unity amplifier with high input impedance, which acts as a buffer works. When the gate 38 opens, the capacitor charges to the peak voltage of the ultrasonic signal, which occurs during the blanking interval. At point a, the signal has the interference level and temporarily has a lower level Value. The capacitor holds this lower value until the gate in the next repetition period at b again opens. At b the "disturbance" level is higher and this higher level is held until point c. From point c to "to Place d an even higher value is obtained. The falls at d

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Level and a lower value is held up to point e. A flaw echo occurs at point e and this has the effect a much larger value, which is held up to the point f.

The waveform (ν) represents the output of the average value !: il ~ ters 42 is, which has a time constant of about 0.1 seconds and smooths the step changes in the signal level, whereby gives an average value of the level.

The output of differential amplifier 44 represents the difference between the last signal level held by the peak key storage capacitor and the average level. All the signal voltages represent the last signal level as dB above the noise level, so that waveform (vi) is the last Signal level represented as dB above the interference level. The relatively small changes in the signal level of the waveform ■ (iv) cause the dB value to be raised above the interference level and become somewhat more negative or positive. This has no effect on the comparator 46.

An echo signal, which is however large enough to be used as a fault signal being interpreted (e on waveform (iv)), however, causes the "dB noise signal" to be the predetermined The threshold value at the input of the comparator 46 exceeds and the comparator then starts the analog-to-digital converter

The analog-to-digital converter forms the "dB noise level signal" into the corresponding 6-bit binary number and a maximum It takes 80 microseconds to perform this procedure. Waveform (vii) shows that the analog-to-digital converter output to the data line via tristate buffer 50 for the duration of the gate pulse of the previous one Connected in the next repetition period. Then the analog-to-digital converter is available to any Receive input from the next cycle.

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The ultrasound probe moves: only moves slowly across the surface of the turbine disk and the changes in cross-section are slowly detected by the ultrasonic scanning system. Even if the If the turbine disk were eccentric, it would take a full turn to create a new boundary layer under the probe and this takes about a second at the highest test speeds. If a geometry echo in the area of the Signal treatment channel according to Figure 5 occurs, has this Geo-.metrieecho an effect similar to the small changes in noise level as seen in sections a through d of waveform (iv) in FIG Figure 5 is shown. The echo signal strength increases only slowly and the low-pass filter 42 with the time constant of 0.1 see effectively follows the increasing signal strength. Accordingly, the "noise signal" remains too small to reach the threshold value and the geometry echoes are ignored.

The analyzer has two input signals, namely the ultrasonic signal, which is to be treated (VIDEO IN) and a trigger signal · (TRIG IN) and three output signals, two of which support the working of the analyzer. this are the output of the logarithmic amplifier 56 (VIDEO OUT) and the blanking pulses, which are shown as waveform (ii) in FIG are. The third output is the multipath connection to the printer 24 and / or the computer 34.

The signals to be treated are rectified and filtered ultrasonic signals and it is essentially the signals that are shown on the oscilloscope screen of the defect detector.

The TRIG-IN input must be a trigger signal which is synchronous runs with the flaw detector transmitter output pulse or is a fixed period of time away from it. A trigger pulse, which occurs shortly before the transmitter pulse can be adjusted by adjusting the delay control (FIG. 7). A later trigger pulse must occur before the turbine disk top surface echo occurs when the echo-triggered output

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probe pulse mode of operation is used.

The VIDEO-AüS output can be used by the oscilloscope 64 together with the
GATE PULSE output can be shown to monitor proper triggering of the gate pulses relative to the front wall echo of the turbine disk. The blanking pulse width can be adjusted to ensure that the blanking pulse train all
contains ultrasonic signals of interest. The operator can also determine whether the gain settings of the flaw detector and analyzer are such that; the defects in the turbine disk result in an increase in the VIDEO OUTPUT signals in the correct dynamic range.

The analyzer can be used in different ways, depending
according to the task at hand and the way of working
is determined by analyzer control inputs (Figure 7).

In the first operation, just described, the mode control is set to "normal", the blanking pulse width is set uniform, and the blanking pulse trigger is set to echo trigger. The first gate pulse is triggered by the first echo pulse received at the VIDEO-IN input after the trigger pulse occurs at the TRIG-IN input. The blanking pulses all have the same
Duration and width can be controlled by the blanking pulse control stage
between about 100 η see and 1.0 y see.

For reasons of convenience, the GATE-PULSE output should be displayed on the screen of the defect detector 62 together with the ultrasonic signals so that (a) are detected
can determine whether the gate pulses start when the surface echo hits and (b) the uniform width is set so,
that the blanking pulse train includes all ultrasonic echoes of interest; and that the blanking width has a value
which is suitable for depth calibration. Instead of this

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can use the VIDEO OUT and the GATE-PULSE outputs on an oscilloscope 64 so that options (a) and (b) can be carried out.

The head amp switch is used to set the VIDEO OUT signals within the dynamic range of the analyzer. The speed of the workpiece 68 is set so that that the width of the repetition pulse frequency of the defect detector detects a defect at least three times when this passes under the probe.

The size of the flaw echo is expressed as dB above the average noise level provided that this value exceeds the setting of the threshold switch. Each Whenever a flaw is detected, the corresponding flaw depth is displayed and is uniform in this case In operation, the depth is measured in terms of time slots corresponding to the blanking pulses. These

] Defects are also added to the defect count.

adds.

} In normal operation, the blanking pulse triggering can be delayed

j will be so that the first blanking pulse after a delay

triggered, which follows the TRIG-IN trigger pulse. The length the delay is set by the delay control and the start of the blanking pulses can be set against the ultrasonic signals as above checked v / earth.

• Even in the normal operating mode, the blanking pulse width can be controlled by the echo size, the clock 58 controlled by the echo size being used. On which Whenever the first blanking pulse is triggered, the blanking pulse width is then controlled by the echo size Latitude control level within the limits between 100 η see and

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1.0 / tsec is set. The width is also determined by the amplitude which influences ultrasonic signals, whereby large signals cause that the width is reduced while the minimum possible width is still 100 η see.

The sensitivity control and the associated width control are used to adjust the clock pulse train so that all ultrasonic signals of interest are detected, with At the same time, it is guaranteed that narrow blanking pulses are always generated when relatively large geometry echoes appear.

The depth of the imperfections is again expressed in terms of the number of pulses measured from the uniform clock pulses.

The analyzer can be used to measure the ultrasonic signals within a selected blanking period or time slot to check and this is achieved by setting the mode switch to echo signals and by setting the desired blanking number or the desired time slot is selected. The analyzer now only shows defects in a selected one Blanking intervals are present. If the blanking pulse width is the same, then the blanking intervals are identical to that Number of gates so that both are selectable.

If the blanking pulse width is affected by the echo size, then the blanking number circuit can be used to adjust the .f To choose the number of gaps to be displayed. In the case of a defect of a given depth, the blanking number depends on the size the width controlled by the echo size and the sensitivity control. If there is a flaw in this blanking interval occurs, then their depth is again represented in terms of blanking gaps of the uniform clock pulses.

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In the embodiment example I according to FIG. 8, each channel 10 has instead of digital devices, analog devices and thus the analog-to-digital converter 48 can be omitted in each channel. The input signals from the defect detector pass through an analog-to-digital converter 72 before they reach each channel 10, so that the signals fed to the channels are now in digital form.

The components of the channels 10 now comprise a digital register 74 constituting the tip key storage circuit, a digital averaging filter 76, a first digital comparator 78 and a second digital comparator 20.

The first digital comparator corresponds to the differential amplifier 44 and receives signals from register 74 and average filter 76. The output of the first comparator represents the · "dB noise protection level", which is fed to the second comparator 80 which corresponds to the comparator 46. The comparator also receives the threshold signal from device 45.

The "dB- ^f J noise" signal is also fed to the three-state buffer stage 50, which is only set by the output of the AND GATE 82, the inputs of which are formed by the output of the shift register and the preceding gate circuit and the output of the second comparator 80 will. Accordingly, the AND GATE switches the tri-state buffer to receive the "dB noise" signal only when there is an output from the second comparator 80, and this latter output occurs only when the "dB noise" signal exceeds the threshold . Otherwise, the signal analyzer is designed in the same way as described in connection with FIGS. 1 to 7 and operates in the same way.

The signal analyzer was described above in connection with the inspection of a turbine disk of a gas turbine engine

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described. It is clear, however, that the invention can also apply to others Workpieces come into consideration where there is a change in cross-sectional area to be considered.

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Claims (17)

Patent Attorneys.: .. ·. "· \, ~ .: .. '-Dipl.-Ing. Curt WaI laughs -. u β ♦ ». ♦. Dipl.-Ing. Günther Koch European patent representative i ~ » _,, ... Dipl.-Phys. Dr Tino Haibach European patent attorneys rj Dipl.-Ing. Rainer Feldkamp D-8000 Munich 2 Kaufingerstraße 8 Telephone (0 89) 2 60 80 78 Telex 5 29 513 wakai d Rolls-Royce Limited Date: January 26, 1983 Buckingham Gate our sign: London SWlE 6AT / England Ultrasonic Defect Detector Signal Analyzer Patent claims: f IJ Ultrasonic flaw detector signal analyzer with several signal processing channels, characterized in that each channel receives the signals to be analyzed via a gate, that the gates can be actuated by a blanking control in order to sequentially follow the signals to be analyzed for each channel the signal processing channels that each channel has a hold circuit that receives and holds the peak value of the signal in the corresponding time blanking interval, that an average filter receives the output of the hold circuit / that a first comparator receives the outputs of the hold circuit and the average filter, the The output of the first comparator is fed to a second comparator which also receives a threshold signal and that the output of the second comparator is used to determine whether the signal of the first comparator is meaningful or not and, if it is meaningful, the output of the first Comparator recorded. 2. Signal analyzer according to claim 1, characterized in that for analyzing the signals generated by the ultrasonic flaw detector of a workpiece testing machine, the output of each average filter represents the average noise level of the corresponding processing channels, that the output of the first comparator is the difference between the last signal level which is held by the holding stage and represents the average noise level and that the output of the second comparator determines whether the output of the first comparator exceeds the threshold value or not. 3. Signal analyzer according to claim 1, characterized in that the blanking control has at least one clock circuit has, which is actuated by a trigger pulse that the clock blanking pulses a Shift register which opens the gate of each treatment channel in succession and that the time during which each gate is held open is determined by the width of the gate pulses generated by the clock. 4. Signal analyzer according to claim 2, characterized in that at least two clock generators are provided that the blanking pulse gap generated by one of the clock generators is the same for all channel gates and Can be set between limit values depending on the number of channels available and according to the thickness of the workpiece to be checked and also according to the smallest width of the signal which is to be checked is. 5. Signal analyzer according to claim 4, characterized in that the blanking pulse gap generated by one of the clock generators is generated, is controlled by the echo size and depends on the size of the echo signal of the Workpiece changes in such a way that the blanking pulse gap is narrow in the area of the geometry echo, so that each processing channel has a shorter period of time for the echo signal in the region of a sharp change in cross section of the workpiece using the uniform timing to determine the depth to measure the defect via a counter circuit. 6. Signal analyzer according to claim 4, characterized in that the two clock generators are set so that trigger pulses from the transmitted signals of the error detector via a time delay or from the Echo signals are obtained from the defect detector and that the input of the shift register from the outputs the two clock generators is controlled. 7. Signal analyzer according to claim 1, characterized in that the signal from the blanking control to the signal processing channel is designed so that the signal is deleted which is stored in the hold circuit of the next following channel. 8. Signal analyzer according to claim 1, characterized in that the digital data generated in each channel via a three-state buffer after a display device and / or a printer and / or be transmitted to a computer via one or more data lines. 9. Signal analyzer according to claim 8, characterized in that the signal of the gate has the buffer with three states of the next treatment channel. 10. Signal analyzer according to claim 1, characterized in that the holding circuit comprises a capacitor and that the first comparator has a differential amplifier and that the second comparator is an analog comparator is. 11. Signal analyzer according to claim 10, characterized in that the capacitor circuit has a capacitor and a Contains buffer. 12. Signal analyzer according to claim 1, characterized in that the signal processing channel is an analog-to-digital converter which receives the output signals from the first comparator when the converter is through the Output of the second comparator is enabled and that the signal from the gate to the one treatment channel is designed so that the analog-to-digital converter enables the same processing channel will. 13. Signal analyzer according to claim 1, characterized in that the signals to be analyzed by an adjustable Amplifier or attenuator and a logarithmic amplifier are processed before they be checked by each signal processing channel. 14. Signal analyzer according to claim 1, characterized in that the key memory circuit has a digital register and that the first and second comparators are each a digital comparator. 15. Signal analyzer according to claim 14, characterized in that that the output of the second comparator is fed to a logic switching stage, the output of which is a Enables three state buffer to get the output from the first comparator when the Output of the first comparator exceeds the threshold level. 16. Signal analyzer according to claim 15, characterized in that the logic switching stage has an AND gate, one input of which comes from the blanking control of the previous signal processing channel. 17. Signal analyzer according to claim 14, characterized in that the signals to be analyzed by an adjustable Amplifier or attenuator and an analog-to-digital converter are processed before they are checked by each signal processing channel.