JP2009204398A - Waveform measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a waveform measuring device capable of automatically executing ensuring flatness at every use without selecting connecting cables. <P>SOLUTION: A waveform measuring device comprises: a probe part provided with a contact pin where input signal is given, a cable loss compensating circuit where frequency characteristics are controlled by adjustment voltage, and a connecting cable with a predetermined length; and a measuring part having a signal processing part which performs operation processing with the output signal of the probe part input. The signal processing part comprises: a first gain-holding means holding the gain to the first signal, where the loss due to the cable is negligible, given to the contact pin: a second gain-holding means holding the gain to the high frequency second signal given to the contact pin; and a cable loss compensating means applying the adjusting voltage to the loss compensating circuit, thereby the gain to the second signal is within the predetermined region of the gain to the first signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention calculates a probe part having a contact pin to which an input signal is applied, a cable loss compensation circuit whose frequency characteristics are controlled by an adjustment voltage, and a connection cable of a predetermined length, and an output signal of the probe part. The present invention relates to a waveform measuring apparatus including a measurement unit having a signal processing unit to process.

  Regarding the configuration of a waveform measuring apparatus typified by a digital oscilloscope or the like, Patent Document 1 has a technical disclosure. FIG. 5 is a functional block diagram showing a configuration example of a probe unit of a conventional waveform measuring apparatus. The waveform measuring apparatus includes a probe unit 10 and a measuring unit 20.

  In the probe unit 10, an input signal is applied between the contact pin 11 and the ground pin 12, divided by the voltage divider 14 in the probe tip 13, and then amplified and output by the amplifier 15.

  The output signal passes through the connector 16 and is connected to the input terminal 18 of the interface P with the measurement unit 20 via the connection cable 17 such as a coaxial cable. The connection cable 17 that connects the probe tip 13 and the measurement unit 20 has a loss due to conductor loss that is proportional to the square root of the frequency (∝√f). This loss deteriorates the flatness of the gain-frequency characteristic of the signal path.

  FIG. 6 is a functional block diagram showing a basic configuration of a conventional probe unit having a cable loss compensation circuit. A cable loss compensation circuit 19 is provided between the voltage divider 14 and the amplifier 15 in the probe tip 13 to improve flatness.

  On the other hand, there is a probe tip portion 13 that is soldered to a substrate to be measured and makes contact with the probe tip portion 13, and has a structure that can be separated from the connection cable 17 by a connector 16. As a result, there is an advantage that, for example, a plurality of locations can be efficiently measured by simply soldering the probe tip to different locations on the measurement target substrate and switching the connection cables.

  FIG. 7 is a functional block diagram showing a basic configuration of a conventional probe unit having a cable loss compensation circuit having a function of adjusting frequency characteristics. The frequency characteristic of the cable loss compensation circuit 19 provided in the probe tip 13 can be controlled by the adjustment voltage Vs. When exchanging the probe tip, the user manually changes the adjustment voltage Vs to correct the frequency characteristics.

  FIG. 8 is a circuit configuration diagram showing an example of a cable loss compensation circuit 19 having a function of adjusting frequency characteristics. The input signal is input to the amplifier U1 having a gain of 1, and also input to the amplifiers U2 and U3 having a predetermined gain via the high-pass filters HPF1 and HPF2.

  The output signals of these amplifiers U1, U2 and U3 are added and inputted to a variable gain amplifier U4 whose gain is controlled by the adjustment voltage Vs, and an output signal whose frequency characteristics are adjusted by the adjustment voltage Vs is obtained.

JP 2003-107107 A

The conventional waveform measuring apparatus has the following problems.
(1) There is variation in the loss of connection cables. Therefore, when the loss compensation is fixed as shown in FIG. 6, if the combination of the probe tip and the connection cable is changed, appropriate compensation cannot be performed.

(2) Also, if loss compensation is fixed and an attempt is made to secure flatness, it is necessary to suppress the loss variation of the connection cable. For this purpose, it is necessary to select connection cables, which increases costs.

(3) In order to solve these problems, there is a method to adjust the frequency characteristics on the probe side as shown in FIG. 7, and there is a method to adjust on the user side for each target cable. This increases the cost for the user.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to realize a waveform measuring apparatus capable of automatically ensuring flatness every time it is used without selecting connection cables. .

In order to achieve such a subject, the present invention has the following configuration.
(1) a probe unit having a contact pin to which an input signal is applied, a cable loss compensation circuit whose frequency characteristics are controlled by an adjustment voltage, and a connection cable having a predetermined length;
A measurement unit having a signal processing unit for inputting and processing the output signal of the probe unit;
In the waveform measuring apparatus comprising
The signal processing unit
First gain holding means for holding a gain with respect to a first signal, which is given to the contact pin and in which loss due to the cable is negligible;
Second gain holding means for holding a gain for a high-frequency second signal applied to the contact pin;
Cable loss compensation means for applying to the cable loss compensation circuit the adjustment voltage that a gain for the second signal is within a specified range of the gain for the first signal;
A waveform measuring apparatus comprising:

(2) The signal processing unit includes an A / D converter that inputs an output signal of the probe unit, an acquisition memory that holds the converted digital data, an arithmetic processing unit that acquires the held digital data, The waveform measuring device according to (1), further comprising a memory used by the arithmetic processing means, wherein the gain for the first signal and the gain for the second signal are held in the memory.

(3) The signal processing unit outputs a switching control signal to switch means for selectively giving the first signal and the second signal to the contact pin through a contact pin connection terminal. The waveform measuring apparatus according to (1) or (2).

(4) The waveform measuring apparatus according to any one of (1) to (3), wherein the signal processing unit applies a DC voltage signal to the contact pin as the first signal.

(5) The probe unit that measures the output levels of the first signal and the second signal in advance, holds them in the memory, and inputs the first signal and the second signal. The waveform measuring apparatus according to any one of (1) to (4), wherein a gain for the first signal and a gain for the second signal are calculated based on a difference between the output level and the measured value of the output level .

(6) The signal processing unit controls a signal generating unit capable of continuously changing the output frequency in a wide range by a control signal, and selectively gives the first signal and the second signal to the contact pins. The waveform measuring apparatus according to any one of (1) to (5), which is characterized.

According to the configuration of the present invention, the following effects can be expected.
(1) If the amplitudes of the first signal source and the second signal source are measured during adjustment, a high-precision high-frequency signal source is not required.

(2) Since the automatic execution function of adjustment can use resources originally possessed by waveform measurement, such as an oscilloscope, no special mechanism other than the switch means for measuring the amplitude is required. A device can be realized.

(3) Since the adjustment according to the variation of the connection cable is automatically executed from the measurement unit side, it is not necessary to select for matching the characteristics of the connection cable.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of a waveform measuring apparatus to which the present invention is applied. The same elements as those of the conventional apparatus described with reference to FIGS.

  The interface P between the probe unit 10 and the measurement unit 20 is provided with a contact pin connection terminal T1 and an adjustment voltage output terminal T2 that are unique to the present invention. The contact pin connection terminal T1 contacts the contact pin 11 during adjustment. The adjustment voltage Vs given from the measurement unit 20 to the adjustment voltage output terminal T2 is connected to the cable loss compensation circuit 19.

  In the measurement unit 20, the signal processing unit 100 (a portion surrounded by a broken line) is connected to the input terminal 18 that receives the output signal of the probe unit 10. This signal processing unit is the same as a component of a normal digital oscilloscope.

  The signal processing unit 100 includes an A / D converter 101 that inputs an output signal of the probe unit 10, an acquisition memory 102 that holds the converted digital data, and an arithmetic processing unit 103 that acquires the held digital data. And a memory 104 used by the arithmetic processing means 103.

  The components unique to the present invention in the measurement unit 20 include a first signal source 200 realized by a DC voltage source, a second signal source 300 realized by a high-frequency signal source, and the voltage of these signal sources by a control signal C1. The switch means SW1 which is switched and applied to the contact pin connection terminal T1 and the D / A converter 400. The D / A converter 400 converts the digital set value Ds of the adjustment voltage given from the arithmetic processing means 103 into an analog value Vs and outputs it to the adjustment voltage output terminal T2.

  In this embodiment, it is assumed that the output amplitude VDC1 of the first signal source 200 and the output amplitude VAC1 of the second signal source 300 are known and stable, and these values are stored in the memory 104 as parameters in advance. Shall.

  The cable loss compensation circuit 19 can compensate for the attenuation characteristic of k√f (k is a proportional constant), and can cope with variations in k by changing the adjustment voltage Vs applied from the measurement unit 20 side. To do.

  The adjustment procedure will be described below. When the adjustment is performed, the contact pin 11 of the probe unit 10 is brought into contact with the contact pin connection terminal T1 of the interface P.

  The switch means SW1 is connected to the contact A by the control signal C1, and the signal processing unit 100 measures the output amplitude of the probe 10 with respect to the first signal source 200. From the measured value VDC2 and the known value VDC1, the probe unit 10 The gain G 1 for the first signal source 200 is calculated and stored in the memory 104.

  Next, the switch means SW1 is connected to the contact B according to the control signal C1, and the signal processing unit 100 measures the output amplitude of the probe 10 with respect to the second signal source 300. From the measured value VAC2 and the known value VAC1, The gain G2 of the probe unit 10 with respect to the second signal source 300 is calculated and held in the memory 104.

  The calculating means 103 ends the adjustment if G2 is within the specified flatness range with respect to G1. If it is outside the specified range, the set value Ds of the D / A converter 400 is changed by a predetermined amount, the output amplitude of the probe unit 10 is measured, and this is repeated until the gain G2 of the second signal source falls within the specified range. With the above operation, cable loss is compensated and flatness is ensured.

  FIG. 2 is a functional block diagram showing another embodiment of the waveform measuring apparatus to which the present invention is applied. In this embodiment, a case where a stable signal source cannot be secured in the measurement unit 10 as the first signal source 200 and the second signal source 300 is shown.

  The switch means SW2 which is switched by the control signal C2 from the arithmetic processing means 103 is connected to the input of the A / D converter 101, and the output signal of the probe section 10 from the input terminal 18 or the contact B via the contact A. The amplitude of the output signal of the switch means SW1 given to the contact pin connection terminal T1 via is selectively measured.

  First, in a state where the switch means SW2 is operated to the contact B, the switch means SW1 is operated to the contact A to measure the amplitude of the first signal source 200, and this value VDC1 is held. Further, the switch means SW1 is operated to the contact point B to measure the amplitude of the second signal source 200, and this value VAC1 is held in the memory 104.

  Next, in a state where the switch means SW2 is operated to the contact A, the switch means SW1 is operated to the contact A to measure the output amplitude of the probe unit 10 that inputs the first signal source 200, and this value VDC2 is held. Further, the output amplitude of the probe unit 10 that inputs the second signal source 300 is measured by operating the switch means SW 1 to the contact point B, and this value VAC 2 is held in the memory 104.

  The arithmetic processing means 103 calculates a gain G1 for the first signal source 200 of the probe unit 10 from the stored values of VDC1 and VDC2, and stores the gain G1 in the memory 104. Similarly, the arithmetic processing unit 103 calculates the gain G2 of the probe unit 10 with respect to the second signal source 300 from the stored values of VAC1 and VAC2, and stores the gain G2 in the memory 104.

  FIG. 3 is a functional block diagram showing still another embodiment of the waveform measuring apparatus to which the present invention is applied. In the embodiment of FIGS. 1 and 2, a DC power source is illustrated as the first signal source 200. However, in FIG. 3, a signal source 500 having a low frequency such that the cable loss of the connection cable 17 can be ignored is used as the first signal source. It is characterized by the configuration.

  FIG. 4 is a functional block diagram showing still another embodiment of the waveform measuring apparatus to which the present invention is applied. In the embodiment shown in FIGS. 1 to 3, the switch means SW1 switches between the first signal source and the second signal source and supplies them to the contact pin connection terminal T1, but in FIG. The output frequency of the signal generating means 600 that can be changed to the above is changed by the control signal C3 of the arithmetic processing means 103.

It is a functional block diagram which shows one Embodiment of the waveform measuring apparatus to which this invention is applied. It is a functional block diagram which shows other embodiment of the waveform measuring apparatus to which this invention is applied. It is a functional block diagram which shows other embodiment of the waveform measuring apparatus to which this invention is applied. It is a functional block diagram which shows other embodiment of the waveform measuring apparatus to which this invention is applied. It is a functional block diagram which shows the basic composition of the probe part of the conventional waveform measuring apparatus. It is a functional block diagram which shows the basic composition of the conventional probe part which has a cable loss compensation circuit. It is a functional block diagram which shows the basic composition of the conventional probe part which has a cable loss compensation circuit provided with the adjustment function of a frequency characteristic. It is a circuit block diagram which shows an example of the cable loss compensation circuit provided with the adjustment function of a frequency characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Probe part 11 Contact pin 12 Ground pin 13 Probe tip part 14 Voltage divider 15 Amplifier 16 Connector 17 Connection cable 18 Input terminal 19 Cable loss compensation circuit 20 Measuring part 100 Signal processing part 101 A / D converter 102 Acquisition memory 103 Operation processing Means 104 Memory 200 First signal source 300 Second signal source 400 D / A converter SW1 Switch means

Claims (6)

A probe unit having a contact pin to which an input signal is applied, a connection cable of a predetermined length, and a cable loss compensation circuit whose frequency characteristics are controlled by an adjustment voltage;
A measurement unit having a signal processing unit for inputting and processing the output signal of the probe unit;
In the waveform measuring apparatus comprising
The signal processing unit
First gain holding means for holding a gain with respect to a first signal, which is given to the contact pin and in which loss due to the cable is negligible;
Second gain holding means for holding a gain for a high-frequency second signal applied to the contact pin;
Cable loss compensation means for applying to the cable loss compensation circuit the adjustment voltage that a gain for the second signal is within a specified range of the gain for the first signal;
A waveform measuring apparatus comprising:   The signal processing unit includes an A / D converter that inputs an output signal of the probe unit, an acquisition memory that holds the converted digital data, an arithmetic processing unit that acquires the held digital data, and the arithmetic processing The waveform measuring apparatus according to claim 1, further comprising: a memory used by the means, wherein the gain for the first signal and the gain for the second signal are held in the memory.   2. The signal processing unit outputs a switching control signal to switch means that selectively applies the first signal and the second signal to the contact pin via a contact pin connection terminal. Or the waveform measuring apparatus of 2.   The waveform measuring apparatus according to claim 1, wherein the signal processing unit applies a DC voltage signal to the contact pin as the first signal.   The signal processing unit measures the output levels of the first signal and the second signal in advance, holds them in the memory, and outputs the output level of the probe unit that inputs the first signal and the second signal. 5. The waveform measuring apparatus according to claim 1, wherein a gain for the first signal and a gain for the second signal are calculated based on a difference from the measured value.   The signal processing unit controls a signal generating unit capable of continuously changing an output frequency in a wide range by a control signal, and selectively supplies the first signal and the second signal to the contact pin. The waveform measuring apparatus according to claim 1.

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