DE1908216A1 - Measuring device - Google Patents

Description

Faiarehild Camera &
Instrument Corporation
464 Ellis Street
Mountain View / Calif. 94040

UNITED STATES..

Measuring device. . "'>»,

The invention relates to the measurement of voltage and Time values as well as similar physical quantities.

Periodic measuring instruments are known for measurements of this type. However, these instruments are relatively imprecise when making high frequency measurements, and this is primarily due to non-linearities, drift, and gain errors. The inaccuracies can be partially compensated for by calibrating the system by hand before each reading. Such an approach is inherently time-consuming and costly, and it is practically impracticable when many. Readings are to be taken one after the other. It should also be taken into account that when a single instrument is used which is successively connected to several different active elements or test circuits, these elements, test circuits, etc. introduce a new variable into the operation. The _t inaccuracy of the system is additionally increased. A typical example of a measurement problem requiring repeated readings is the case of examining a transistor or an integrated circuit. Investigations of this kind require repeated high-frequency measurements (e.g. voltage, rise time, distribution delay) via various active elements, test circuits, etc. (e.g. 1 GHz) or a very short time (e.g. 1 nanosecond); permitted;

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1S0821S

According to the invention is a measuring device; vcprgeselieniiiii: one? Calibration circuit for supplying at least one self-signal: a memory for storing signals, waä. for supplying an output variable which indicates the relationship between the stored signals, a measuring device: two measurement of a characteristic variable of an input signal and for supplying a corresponding output signal for storage in the memory, the calibration circuit and the output signal with the memory via the measuring device and the measuring device is in connection with the memory.

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With a similar device, voltage values of impulses and Wecfoselstörom waveforms can be measured, the frequency of which is in the order of 1 KHz to 1 GHz, or time measurements in the order of one janosecond up to a million band, the attainable level being Accuracy; better than -1 % is fc *. A particular advantage is that these measurements can be repeated, carried out without the need for manual calibration. The device hardly has many different elements or test circuits can be used in a multiple position measurement without further calibration being required. The problem of temperature control, drifting disks and non-linearity: is practically solved by the device according to the invention. "

Embodiments of the invention are illustrated with reference to the lines described below. .

Pig. 1 shows jit in a simplified manner of representation .. Bockscha-l ±> - * - image of the overall system of the invention.

Fig. 2 shows a "block diagram of the Eiasriclatiiaggeiafte the invention, with more details of the memory wxä the M © i3 -vorrichtHngr? Shown".

Fig. 3 shows the. Establishment according to the Srfiaduag in fiteren Details. "/,.-." aei ^ '-.

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In the general representation according to FIG. 1, the device according to the invention contains a measuring device or measuring circuit 10 for measuring a characteristic property an input signal and for supplying a representative therefor Output signal. The measuring circuit 10 can with an input terminal 12 are connected via which a to measuring input signal is supplied, and with an input terminal 14, via which a calibration or reference input signal is to be delivered. Switch 16 can be used as a tongue relay or as a Pest body switch be formed. The measuring circuit 10 has a further input 13 which is connected to a calibration circuit 60. The output of the measuring circuit 10 arrives at a memory 20 and to the calibration circuit 60 «memory 20 is available with an output circuit 44 in connection.

As can be seen from FIG. 2, the measuring circuit 10 can contain an active test circuit 15, for example an FET / MOS impedance matching or foiling. The active test circuit 15 is in turn connected to a scanning circuit 17 which, for example, is a Tetronik 3S76 scanning bridge or another may be suitable circuit, for example, as shown in the U.S. Patent 3,124,746 (J. Strathman, issued Oct. March 1964). The Tetrpnik sensing bridge contains a pulse shaper 18, which can be used, for example, as a pulse extension or pulse correction circuit can be formed. The sampling circuit 17 and the active test circuit 15 are high-frequency circuits which supply the terminals 12 and 14 Scan the signal at an extremely high speed and can provide an output signal which the Amplitude of the signal sample at the moment of sampling is proportional. The output of the sampling circuit 17 arrives to the pulse shaper 18 and is there of a duration in the Order of magnitude from microseconds to nanoseconds at a time

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Lent length in the order of milliseconds gastr © ekt. The greater duration of the I & puises is required for the memory 20; which is connected to the output of the measuring circuit 10

In the measuring circuit 10 there is also a generator 19, which is connected to the scanning circuit 17 and this delivers a suitable pulse when it is triggered or triggered by the calibration circuit 60 (FIG. 2). The pulse generator 19 receives input signals over Bingangsklemme 11 which kanrt associated with a clock generator in conjunction> will be described in more detail below _o addition to illustrate provision of a pulse for the operation of the scanning circuit 17 provides the Abtastimpüleerzeuger 19 an output signal for the calibration circuit 60, which for ₄ ensures that the calibration circuit starts another operation. >

The memory 20, which is connected to the output of the measuring circuit 10 (Fig. 1) is connected, stores signals received from the measurement circuit during their connection to the input terminals 12 and 14 are delivered. Memory 20 supplies an output signal, which in a certain proportion to the different stores there are no signals. As can be seen from FIGS. 2 and 3, the memory 20 contains a plurality of memory parts 22, 24 and 26, which selectively with the measuring circuit 10, namely with pulse shaper 18 via a suitable switch 27, in connection stand. The switch 27 is shown schematically as a mechanical switching arrangement, but this switch is preferred as a tongue relay, as an electronic switch, ale solid-state switch or the like. «The output of the memory parts 22, 24 and 26 is associated with a pair of comparators gen or comparison circuits 28 and 29 are connected. As in As shown in FIG. 2, the output of the storage part 22 is

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connected to the comparison circuits 28 and 29, and the off « Gang of the memory part 24 is only available with the comparison circuit 28 in connection, while the output of the memory part 26 with the comparison circuit 29 is connected. These outputs can also be connected or switched in another suitable manner in order to achieve the same results taking into account the particular To achieve properties of the system.

The outputs of the memory parts are switched in such a way that if the stored values in two memory parts (e.g. memory parts 22 and 24) coincide, a comparison circuit (e.g. 28) supplies a suitable signal to a gate circuit 30. Following the actuation of the gate circuit 30, all pulses pass the _# to the storage parts 22, 24 and _r 26 are applied by the memory parts and the comparison circuits for Eichschaitung 60 and to the output 44. "The system can also like this. be designed or operated so that, as shown in FIG. 2, a coincidence can also be taken into account in the case of a second stored fourth. If there is coincidence, a signal is generated and gate 3Q is operated to terminate the passage of signals or pulses. In this connection, it should be noted that the output of the comparison circuit 28 can be used to terminate the passage of pulses through gate circuit 30, while comparison circuit 29 is used to initiate the passage of pulses'.

In the context of the invention it is also possible that the comparison » circuits 28 and 29 under the same coincidence conditions are made to respond at the same time, but one the two comparison circuits deliver a delayed signal, so that the gate is opened for a single pulse. Such a design or mode of operation may be desirable,

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if the measuring circuit is programmed to have a single Searches for a value, for example a peak value or a certain time value, in such a case the passage of a single pulse through the gate circuit 30 indicates that a such value exists. The memory parts 22, 24 and 26 together with the comparison circuits 23 and 29 can be a Deliver a signal (a number of impulses) which correct value which is measured by the measuring circuit 10 is proportional. In connection with the invention this requires *? ort "coincidence" does not necessarily mean the state of equality, that is, "but it is to be understood in a broader sense that several predetermined conditions exist, which a predetermined Achieve an effect, for example an output signal with various characteristic features. This is shown below to be explained in more detail «

In one embodiment of the invention, the memory parts 22, 24 and 26 can be designed as function amplifiers, with an external memory capacity being available which is sufficient to store a signal for a few or many milliseconds. In the context of the invention may auelh be used ander® types of memory devices, for example, _B solid state "memory or magnetic memory.

The output of the memory 20 is connected to an output circuit connected .. In the embodiment of Fig. 2, the output circuit includes an electronic digital counter 46 " its output with a suitable display device 48 for Display of the result of the measurements connected. counter and Display devices of this type are known and are available various execution formats available.

The calibration circuit 60 supplies a reference or self signal Singangsklemme 14, and it also supplies © in For tschalt = or

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Trigger signal to the sampling pulse generator 19. In the embodiment according to FIG. 3, the filter circuit 60 contains a comparison trigger circuit 62, the output of which is connected to the sampling pulse generator 19. The inputs of this circuit lead to a digital-to-analog converter 64 and a function generator or " fast ramp * generator 66. The converter 64 is in turn connected to a digital counter circuit 68 which supplies a digital input to the converter € 4 «Counter 68 is also connected to the sampling pulse generator 19 and gate 30. Function generator 66 is connected to a delay circuit 70 in Connection: which supplies a signal there, which is the signal of the -. " Function generator delayed by a programmed amount «The delay signal of the delay circuit 70, the falling signal of the function generator 66 and the strength of the output of the digital-to-analog converter 64 are programmed to different values by a programming circuit SO, which supplies the corresponding inputs. The program circuit can be designed in a suitable manner, for example with a magnetic tape or disk memory with the associated circuits, electronic data processing systems or card reading devices with the associated pearl devices can be present. circuit or an electronic data processing system, such as is used, for example, in the SOOO Fairchild Instrumentation Automatic Test Center series for integrated circuits and modules.

A second digital-to-analog converter is located within the filter circuit 60 72 present and connected to a counter 74. This digital-to-analog converter and the counter are from the digital-to-analog converter 64 and the counter 68 are shown separately in order to simplify the description of the mode of operation. At a preferred embodiment work the digital-to-analog converter

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64 and the counter 68 with the gaste utens shown in FIG. 3 are suitable Time division multiplex connections as converter 72 and counter

The circuit described operates in such a way that the digital-to-analog converter 64 supplies a signal to the comparison trigger circuit 62 when a signal is applied by the program circuit 50 and counter 68. This signal is proportional to the output signal of the counter 66 or has a definite relationship to its strength and is compared with the signal S sent by the function generator 66, which is controlled by the program circuit 50 and the delay circuit 70. The program circuit 50 primarily determines the inclination and characteristic properties of a function generated by the function generator 66, and the delay circuit 70 determines the time at which such a function is initiated if the function generator 66 and the digital = analog - Converter 64 delivered signals. Coincidence exists / - the comparison trigger circuit 62 delivers a pulse to the sampling pulse generator 19, The Xnipulserz @ ug © r 19 in turn actuates / the ^ sampling circuit 17 and counter 68, which in turn the output of the converter 64 for the next - "Sampling. Increased" digital-to-analog converter 72 delivers a reference or "self-signal to the lingaagskiemme 14? The control is carried out by Frograimn circuit 50 «. From the following description of the mode of operation of the d @ ® system will emerge, - SaS converter 64 and Züifer 68 and converter 72 and counter 74 are not used at the same time,. - \ ■ '..- ~ ^: ■ ,. . ' - ■ ^:

There are several available for the application of the peeling system described advantageous options available «As the first type of application consider the case that the circuit die'.Time between measures two Spaaniang values V 1 and V 2. It is assumed that the rise time of a pulse between values - from Γ volts

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and 3 volts is to be measured. Then the program circuit 50 will first set the converter 72 to a word of 1 volt. Active test circuit 15 is connected to terminal 14 and converter 72 so that the 1 volt reference signal is received at approximately the same time that a train of pulses is applied to strobe generator 19 via terminal 11 from a clock generator (not shown). These pulses reach the sampling pulse generator 19 and cause it to pass a pulse to the sampling circuit 17 so that a reading of the 1 volt signal which is supplied by the converter 72 to the active test circuit 15 is taken. The measurement obtained by the sampling circuit 17 arrives at the storage part 24 via the pulse shaper 18, which stretches the pulse sufficiently to be stored in the storage part 24. Since the test circuit and other active components of the system from the program management 50 to the stored! 1 24 can contain deviations, gain errors and near linearities, the reading stored in the memory part 24 can deviate from the value of 1 volt. For example, assume that the actual reading stored in memory portion 24 is Q.80 volts. If this W @ rt now in the storage part 24 is stored, the converter 72 through the program circuit 50 now to a value of 3 volts programmed follows iffssanfeliehen the same i ^ beitsgang · Then, as he ®T been described ±, _s however, with: the exception that the resulting value, scanned by the scanning circuit 17, is now stored in the memory part 26, the actual reading will again deviate to a certain extent from the programmed value of 3 volts. In the present case, assume that the reading stored in memory 26 is 3 * 1 volts. Storage part 24 and storage part 2δ therefore supply a start reference value of 0.8 volts and a stop reference value of 3.1 volts. In this way, the cycle for this measurement is completed

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. The active test circuit 15 is jetst with Κ1-μα @ @ 12 .verbunden '■ "■ -: around the au se ms sequent or au test signal eispfeogano S ± @ s @@. -

Signal "can, for example, from a _ FSStifcöarpsr-'Einriehtung;, ■" ". ■ -" .- / in particular an integrated circuit., .- of which a character © =

ristisches characteristic measured or getestet'-weräsh "© _oil,:.. are g <ii ~ V provides the control circuit © © © oar ETR .Ste.u®rkr _ff is the switch 16 _s cause die'Kleiams 12 od ©.. r © di -Call with the active test circuit 15 to "also cause _a counter that is set to Mull 68 ,,; wisher. On the other hand, T α the digital toeppenförndgen Äasgaiag of liMsatZers 64 a «f \

- 'an exit with the. Wert Mull h@rabss.tzt <s. The © rstos Irapuls "

from a (not shown) Ta & € g®b @ rsefealtyng _r which süt "delay circuit 70 delivered x» or _r causes _ff daÄ © in delayed impulse to function SS '■' -g © ii @ f © ar ^: t- is _o The delay circuit; 70 is shower -ßi @ ErograMnschsltung 50 causes a ä & n zvm FuAtionsgeaerator .66 g © li @ f © rteza impulse to -..- delay and @icheraiastell <aß _ff fei test the si signal ' dä © r zu t © sfe @ nös Sehwirarnrngsfona -

from the FrograiüisehaltTaisg SO ₄ , x ^ @ lche den. -. "-. Function generator 66 @ t @ u @ rt " f®sfeg @ l @ gt _o Di.® Frograram circuit

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The only © of the VersögeruagsgcK'al'tung 70 ifsitQS ¹ gegeben® pulse sets the FuÄtionagsnerator 66 in Tätigkeit- _e. which delivered & in output signal to trigger circuit 62 '. fJena; d @ r value

Input, is ", which .from the Otesfeser 64.-is delivered to the circuit 62 _s offles · ab®r-Höljer i @ t _ff is v © ad © r.

¥ compare @ <= TEigg @ rsGhaltisRg © 2 ®ia Ts ± ^ q®zim ^ ulm . © szeugt, which ".

Sampling circuit 17 to sample the signal once, which is measured at terminal 12. This © measurement is then introduced into the storage part 22. The & btastimpulsegenerator 19 also provides an output signal to counter 68, see above that this is incremented by one digit and thereby the output of the converter 64 is increased. The next impulse to Terminal 13 in turn triggers the function generator 66, and a further trigger pulse is generated at a point in time in which the output of function generator 66 is equal to the output of converter 64 or higher. The counter 68 is increased by one more Digit advanced, and the new measurement by the scanning circuit 17 is inserted into the storage part 22. This process continues until comparison circuit 28 determines that the values stored in the memory parts 22 and 24 are the same (e.g. 0.8 volts), If this condition is detected, if you address comparison circuit 28 and open the gate 30, so that pulses from the sampling pulse generator 19 through gate 30 and to Counter 46 can be passed on. Every pulse from the pulse generator 19 advances the counter 46 by one digit; the counter 68 is also incremented. The scanning process is continued with each pulse reaching the counter 68 until the comparison circuit 29 has a value of 3.1 volts from the Memory part 22 detects, and this value is equal to that in the Storage part 26 stored value, at this point the actuated Comparison circuit 29, the gate circuit 30, and the activity. of the counter 46 is ended. The number of counts registered in the counter 46 has a certain relationship to the desired one Measurement. For example, if each step of the converter 64 is one millivolt and the rapid rise is am The function generator is equal to 1 millivolt per nanosecond, which represents the number of counts multiplied by one hanosecond desired time measurement.

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The calibration cycle follows in the described mode of operation the measuring cycle via the same measuring circuit 10 (which the active test circuit 15 contains). In this way there are measurement errors essentially eliminated by long-term drift phenomena. In addition, there are non-linearities in the high frequency part (Measuring circuit 10) of the system also essentially remedied by the digital feedback arrangement described, and also gain or displacement errors in the active one Test circuits are switched off. The described inventive The system therefore enables a particularly precise measurement very high frequency signals, with many being consecutive Measurements can be carried out without a calibration of Hand and other time consuming operations are required as are normally required to achieve the highest level of accuracy reach.

Another advantageous application of the measuring device according to FIG of the invention is the voltage measurement between two time reference values to execute. In this case, the active test circuit 15 is initially connected to the measured signal via the terminal tied together. (This is the reverse of what was described above Operation.) The converter 64 is programmed to a first time reference value by program circuit 50, which the output of the converter 64 sets. The function generator 66 is by a clock pulse, which in the already described Way to terminal 13, put into action. The coincidence of the output value of the converter 64 and the output value of the function generator 66 causes the comparison trigger circuit 62 to deliver a trigger pulse to the sampling pulse generator 19. The trigger pulse in turn sets the sampling circuit 17 into action and causes the signal to be applied Terminal 12 is scanned. Then part 24 is a value in the memory stored, which corresponds to the sampled signal. Afterward

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the converter 64 is switched to one by program circuit 50 programmed in a second time reference value, and the function generator 66, the trigger circuit 62, the sampling pulse generator 19 and the sampling circuit 17 repeat in FIG Way their operations so that the signal at terminal 12 is sampled again at a second point in time, and the memory part 26 stores a signal indicative of voltage in the second reference time is representative. At this point in time, the voltage measurement is between two time reference values, and it is stored in the storage parts 24 and 26.

The switch 16 is now connected to terminal 14 and a reference signal tied together. A pulse sets the sampling pulse generator 19 into operation via terminal 11, and this in turn initiates the sampling circuit 17 to sample the reference signal. The sampling pulse generator also switches the counter 74 so that the Output of converter 72 and the reference signal increase » These operations continue, and each sample of the output of the converter 72 is stored in the memory part 22. The value stored in the memory part 22 is compared with the values stored in the memory parts 24 and 26 by the comparison circuits 28 and 29 compared «, As soon as the value of the Memory part 22 becomes the same as that of memory part 24 or higher, the comparison circuit 28 opens the gate 30 so that the pulses from the sampling pulse generator 19 pass through the gate 30 to the counter 46 can. When the output value of the memory part 22 is equal that of the memory part is 26 or higher, the comparison circuit speaks 29, so that the gate 30 is closed and the counter 46 is stopped. The number of counts multiplied by the voltage per stage at converter 72 represents the voltage value of the signal between the two reference times.

Also in this mode of operation described are in the measuring devices of the described system, including the test

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circuit, the scanning bridge and the pulse shaping circuit, which are particularly critical high-frequency circuits ^ non-linearities, drift phenomena and gain errors are eliminated. Essentially, these critical high-frequency circuits are only used as null detectors. All other circuits work in a relatively low frequency range, and high levels of accuracy can be achieved there without difficulty. It is also important that the measuring device according to the invention is relatively insensitive to the ambient temperature. The measuring device according to the invention offers both the advantages of a scanning method in the manner of an evaluation test and of the equivalent time method, so that high-frequency signals can be measured with extremely high accuracy _e

In addition to the methods described are for the invention in There are numerous other possible uses within the framework of professional action to disposal. The measuring device according to the invention can therefore also be used for numerous other measurements can be used, for example, to measure a voltage at a given point in time, to measure voltage differences, for measuring percentage rise times and other measurements of this kind. In these measuring methods, a calibration ^ or Reference cycle a measuring cycle over the same measuring switch.

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Claims (8)

19Q8216 - 15; Claims 1 * Measuring device for measuring either the change in amplitude of a signal in a given time or the time in which the amplitude of a signal changes by a given value, with a measuring circuit for measuring discrete values of the amplitude of an input signal, a comparison circuit for comparing the measured discrete values Values of the input signal amplitude with reference amplitudes, a display device which responds when the measured discrete values of the input signal amplitude are equal to those of the reference amplitudes, and a calibration circuit for calibrating the measuring circuit _; characterized, that the measuring circuit (ΙΟ) successively after receipt of control signals from a program circuit (50) the measurement of both discrete values of the amplitude of the input signal and discrete values of a reference signal allowed, that the comparison circuit contains a memory (20) which stores either certain discrete values of the amplitude of the reference signal or certain discrete values of the amplitude of the input signal, and which stores those which are not stored compares discrete values from the measuring circuit (10) with the stored discrete values from the measuring circuit (10), and which delivers coincidence pulses if the unsaved discrete values are equal to the stored discrete values are, that the display device contains an output circuit (44) which, when coincidence pulses are input, either the change in amplitude of the input signal in a given time, or the time in which the amplitude of an input signal changes by a given value, and - 16 - 90983971004 190821Β ■■■■ '. ■■■ '.'. - 16 - ■ .-; ■■; ■. '■■ -.,. '"■ -. -" that the calibration circuit has a circuit (60) for periodic Actuation of the measuring circuit (10) contains, so that in the storage and comparison circuit (20) new discrete values of the amplitude of the reference signal or the input signal can be measured and stored, with drift phenomena or non-linearities in the measuring circuit (10) are eliminated in the output signal of the output circuit (44). - 2. Measuring device according to claim 1, characterized in that the measuring circuit (1O) contains the following switching elements: a φ sampling circuit, which successively both the input signal for generating measured values of the amplitude of the input signal as well as a reference signal for generating measured values of the Amplitude of the reference signal is sampled and at certain times in action, and a pulse shaper circuit for selective Shaping the sampled values and generating the discrete values of the amplitudes of the input signal and the reference signal. 3. Measuring device according to claim 1 or 2, characterized that the memory and comparison circuit (20) contains the following switching elements: a memory part for storage certain discrete values of the amplitude of either the reference signal or the input signal, and a comparison w circuit for comparing the stored discrete amplitude values with the non-stored discrete amplitude values from the measuring circuit (10) for generating coincidence pulses when the non-stored discrete values are equal to the stored discrete values. 4. Measuring device according to claim 2 or 3, characterized in that the control of the scanning circuit has the following switching elements contains: a sampling pulse generator for generating pulses which cause the sampling to perform a function - 17 ~ 909839/1004 generator for generating a rising voltage with assigned Slope, a signal generator for generating an analog signal which is proportional to the number of pulses, generated by the sampling pulse generator, and a comparison circuit, to compare the analog signal with the rising voltage and to generate an actuation pulse, when the rising voltage is equal to the analog signal, the actuation pulse activating the sampling pulse generator. ". ■" .- 5. Measuring device according to one of claims 2 to 4, characterized in that the circuit (60) for calibrating the measuring circuit . ('1O)' contains the following switching elements: a signaler-. generator for generating a reference signal, and a program circuit, which causes the reference signal to be sampled to the discrete values of the amplitude of the reference signal to generate, the program circuit also including both the inclination the increasing voltage as well as the change in the analog signal when each pulse is received from the sampling pulse generator controls. 6. Measuring device according to one of claims 1 to 5, characterized in that that the output circuit (44) contains a circuit, which on the coincidence pulses from the memory and Comparison circuit (20) responds in such a way that it supplies an input signal which is directly proportional to either the change in amplitude of the input signal in a given time or that is the time within which the Changes the amplitude of an input signal by a given amount. 7. Measuring device, characterized by the following switching elements: a Mett circuit for measuring discrete values of the amplitude of an input signal, one coupled to the measuring circuit Comparison circuit for comparing the discrete values of the amplitude of the input signal with a certain number of stored reference amplitudes, a display circuit for display 909839/10 04 the change over time, which occurs when the amplitude of the input signal changes between the stored reference amplitudes, and a circuit for calibrating the measuring circuit, ταα essentially the effect of drift phenomena and nonlinearities adhering to the circuit components on the measured amplitude values of the input signal and accordingly on the to eliminate temporal changes by periodically inserting new values of the stored reference amplitudes for the old values of the stored reference amplitudes. : 8. Measuring device, characterized by the following switching elements: a circuit for measuring and storing a certain number of discrete values of the amplitude of an input signal in several predetermined times, a circuit for controlling the measuring circuit to sample a reference signal whose amplitude increases linearly with time , a comparison circuit coupled to the measuring circuit for comparing the sampled amplitudes of the reference signal with the stored discrete values of the input signal, which indicates the times in which the sampled amplitudes of the reference signal are equal to one of the stored values of the amplitude of the ν input signal, and a counting device for counting the number of samples of the reference signal between the times in which two sampled amplitudes of the reference signal ₌ are two stored values of the amplitude of the input signal, the counting of the voltage change of the Bingangsignals between two gegebe times is proportional and representative of them. ' 909839/10 04 Lee rs ei t e