JP2018189453A - Input signal converter and measuring device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an input converter for oscilloscopes which is inexpensive and with which it is possible to change the number of input channels in accordance with a test piece, and a measuring device.SOLUTION: The input converter comprises: a plurality of input channels for latching a plurality of analog input signals; an impedance matching unit for performing impedance matching upon receiving each of analog input signals from the plurality of input channels; a sampling frequency adjusting unit for adjusting a sampling frequency when digitizing each of the analog input signals having undergone the impedance matching to a digital sample; an A/D converter for digitizing each of the analog input signals with the regulated sampling frequency to a digital sample; a data memory access unit for storing the digital sample from the A/D converter; and a data transfer unit for transferring the digital sample stored in the data memory access unit to a display device.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an input signal conversion device that takes in an input signal and performs analog-to-digital conversion (A / D conversion), and more particularly to input signal conversion that AD converts a plurality of analog input signals under a predetermined condition and sends them to a display device. The present invention relates to a device and a measuring device including the device.

Measurement devices include devices that measure electrical characteristics such as voltage value, current value, and resistance, and devices that measure environments such as temperature, humidity, luminance, and odor. Although these measuring apparatuses have a difference in measuring current directly or indirectly, all of them measure the input electric signal from the probe by bringing the probe into contact with the device under test.

One measurement device is an oscilloscope. Oscilloscopes are widely used from research and development in companies to personal hobbies because they can observe waveforms and measure signal levels. In recent years, oscilloscopes have changed to digital oscilloscopes in place of old CRT oscilloscopes, analog storage oscilloscopes, and analog oscilloscopes. The digital oscilloscope has a probe that picks up the input signal, an analog input signal input from the probe, converts the analog input signal into analog / digital data, and converts it into data suitable for use in the display unit, and the converted data The display part which displays.

  When using an oscilloscope, the accuracy required by companies for R & D and test measurements differs greatly from the accuracy of personal use. In research and development in a company, first, strict accuracy is required for the measurement waveform, such as the accuracy of the measurement waveform and its reproducibility. On the other hand, the level required for personal use is almost always sufficient if the waveform can be observed rather than strict waveform measurement (measurement). In addition, there are many cases where it is sufficient to perform waveform observation and level measurement to such an extent in a maintenance business trip service for electronic devices. What is important in such a case is that it is small and light and easy to carry, and the price of the device is low.

For this reason, small, low-priced oscilloscopes, called pocket digital oscilloscopes for individuals, have recently begun to be sold on the Internet. For example, it is an ultra-small oscilloscope MINI / NANO described in Non-Patent Document 1 below. This ultra-small oscilloscope is equipped with a full-color TFT LCD screen, is a Max sampling 72MHz, resolution 8bit, 2 or 4 input channel, weighs as low as 80g (excluding batteries), and costs as low as around 10,000 yen. Price.

However, in the ultra-small oscilloscope of Non-Patent Document 1 below, the number of input channels is limited depending on the model (DS202 is 2 channels, D203 is 4 channels). For this reason, there is a problem that input signals having the number of channels corresponding to the state of the device under test cannot be grasped in parallel. Further, in order to change the display method of the waveform displayed on the TFT, it can be operated only in an area having a limited touch panel function such as a touch / slide part. For this reason, there exists a problem that operativity is not necessarily good.

Non-Patent Document 2 below discloses a portable oscilloscope in which a smartphone has a display function. While the oscilloscope of Non-Patent Document 1 is an integrated compact oscilloscope with a display unit, Non-Patent Document 2 has a dedicated adapter for the dock connector of registered trademark iPhone, registered trademark iPad, and registered trademark iPod touch. By connecting, it is finished in a portable oscilloscope kit. The basic function of this oscilloscope kit is a mixed signal type of analog 1 channel and digital 4 channel, and has a performance of a sampling rate of 12 MHz in a band of 5 MHz.

However, the probe connected to the portable oscilloscope disclosed in Non-Patent Document 2 has a problem that it can be used only for a so-called normal probe provided with an impedance matching unit that is indispensable for connection with a smartphone. For this reason, there is a problem that measurement cannot be performed by freely changing the shape of the probe according to the shape of the object to be measured. In addition, since the analog input channel is one channel, there is a problem that a plurality of input signals cannot be observed simultaneously.

Latest Technology: Ultra-Small Oscilloscope MINI NANO “Search April 10, 2017”, Internet <URL: http://www.ktek.jp/sub-pocket-dso.html> Phone and iPad (both are registered trademarks) make an oscilloscope kit appearance "Search April 10, 2017", http://weekly.ascii.jp/elem/000/000/041/41646/

  Accordingly, an object of the present invention is to provide a low-priced measurement device, for example, an input conversion device for an oscilloscope, and a measurement device, which can input a plurality of channels, change the number of input channels according to the device under test. There is. Another object of the present invention is to provide an input conversion device for a measuring device that can freely change the shape of the probe according to the shape of the device under test.

The invention according to claim 1 includes: a plurality of input channels that take in a plurality of analog input signals; an impedance matching unit that receives the analog input signals from the plurality of input channels and performs impedance matching;
According to the number of input channels of the analog input signal, a sampling frequency adjusting unit that adjusts a sampling frequency when the impedance-matched analog input signal is digitized into digital samples,
An A / D converter that digitizes each of the analog input signals into digital samples at a sampling frequency defined by the sampling frequency adjustment unit;
A data memory access unit coupled to the A / D converter for storing the digital samples from the A / D converter;
An input data conversion device comprising: a data transfer unit for transferring a digital sample stored in the data memory access unit to a display device.

A second aspect of the present invention is the input data conversion apparatus according to the first aspect, wherein the sampling frequency adjusting unit sets the sampling frequency of the N channel when the sampling frequency at the time of one channel input is A. A means for adjusting to A / N is provided.

The invention according to claim 3 is the input data conversion device according to claim 1 or 2, wherein the probe connected to the input channel has conductivity, and can be freely shaped according to the shape of the device under test. It is a probe that can be deformed.

  The invention described in claim 4 is connected to the input data converter according to claim 1 or 2, the probe according to claim 3, and the input data converter, and the data from the input data converter is received. An oscilloscope comprising a data display device for processing and displaying graphically.

  The invention according to claim 5 is the oscilloscope according to claim 4, wherein the data display device is a smartphone, and is connected to the input data conversion device by USB (Universal Serial Bus) or wirelessly. And

  The invention according to claim 6 is connected to the input data converter according to claim 1 or 2, the probe according to claim 3, and the input data converter, and the data from the input data converter is received. An oscilloscope comprising a data display device for processing and displaying graphically.

  According to the present invention, it is possible to provide at least four channels or more, change the input channel according to the measurement condition of the device under test, and provide an inexpensive input conversion device for a measuring device and a measuring device. can do. In addition, since the probe used in this input device need only have conductivity, the shape of the probe can be freely changed at the measurement site in accordance with the shape of the device under test. It is possible to provide an input conversion device for a measurement device, for example, an oscilloscope, which can use such a shape-changeable probe.

1 is an overall view of a configuration of an oscilloscope that is an example of a measurement apparatus using an input data conversion apparatus according to an embodiment of the present invention. It is a block diagram of the input data converter which is one embodiment of this invention. It is a block diagram of CPU with which the input data converter which is one embodiment of this invention is provided. It is the whole flowchart of the input data which is one embodiment of the present invention. It is a flowchart of the auto mode in the case of converting the input data which is one embodiment of the present invention. It is a flowchart of the trigger mode in the case of converting the input data which is one embodiment of the present invention It is the figure which showed the change of a display waveform using the touchscreen function of the smart phone connected to the input data converter which is one embodiment of this invention.

Embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is an overall view of a configuration of an oscilloscope that is an example of a measuring apparatus using an input data conversion apparatus 1 according to an embodiment of the present invention.
FIG. As shown in FIG. 1, an oscilloscope using an input data conversion device 1 is connected to the input data conversion device 1 and comes from the probe 3 that touches the device under test 4 and extracts an electrical signal from the device under test. And a USB cable 5 for sending the data to the smartphone 2 as a display device.

  FIG. 2 is a block diagram showing the configuration of the input data conversion apparatus 1 according to the embodiment of the present invention. The input data converter 1 includes an input connector 10 connected to the probe 3, an impedance matching unit 20, a level shift unit 30, a CPU 40, and a USB connector 50. In this embodiment, the number of input channels is four. However, the number of input channels may be one channel or four or more channels depending on the measurement conditions of the device under test.

  The impedance matching 20 is for equalizing the impedance of the circuit of the input data converter 1 and the impedance of the device under test 4 connected to the probe 3. Thereby, the electric power obtained in the circuit of the input data converter 1 can be maximized.

  As a specific circuit, if it is sufficient if the band to be measured is matched only in a narrow band, a matching circuit using a combination of a coil and a capacitor may be used, and impedance matching can be achieved by adjusting the ratio of the capacitor and the coil. It ’s fine. When the band to be measured includes a high band, it is necessary to match the impedance (reactance component) of the imaginary part. Therefore, it is preferable to have a reactance component such as a capacitive component or an inductive component.

  The level shift unit 30 includes an OP amplifier (buffer high input impedance) for outputting the input data from the impedance matching unit 20 as it is (one to one). Further, since the level of the input voltage to the impedance matching unit 20 is ± 1.5 V, a level shift circuit unit 32 is provided to adjust this to the voltage (0 to 3 V) of the CPU 40.

  The CPU 40 generates an AD unit 410 that converts analog data from the level shift unit 30 into digital data, a data memory access unit 411 that stores digital data from the AD conversion unit 410, and a sampling frequency corresponding to the number of input channels. Sampling frequency adjustment unit 412, trigger level detection unit 413 for detecting the trigger level in the trigger mode, trigger time-out timer 415 for canceling the trigger mode when the set trigger value is not detected, data transfer to the smartphone 2 A level shift unit 416 that matches levels, a correction value storage unit 417 that stores correction values for individual differences, a USB controller unit 418 that performs data transmission / reception via USB, and a control program unit 414 that performs these controls.

In the case of the auto mode, the data stored in the data memory access unit 411 is transferred as it is as the data in the data memory access unit 411. On the other hand, the trigger mode, for example, when observing the voltage waveform of the DUT 4 detects the voltage value (level) if you want to start observation when it exceeds a certain voltage value (threshold). The trigger level detection unit performs the observation by providing such a threshold value.

The correction value storage unit 417 has variations in the reference voltage for each input data converter (individual). This is to correct the variation. For example, when it is common that an error of 1% occurs at 10 megaohms, the input data conversion apparatus 1 generates an error of 1.5%. In such a case, since it is necessary to correct the error with the value, the correction value storage unit 417 stores the correction value for that purpose.

As described above, the level shift unit 30 shifts the input voltage from the DUT 4 from ± 1.5 V to 0 to 3 V by the level shift unit 30, but the level shift voltage unit 416 The transmission data when sending to the smartphone 2 is converted so as to have a value of 0 to 30V. That is, the level shift voltage unit 416 matches the level (voltage) of the device that displays data.

  Data subjected to AD conversion at a sampling frequency corresponding to the number of input channels is transferred to the smartphone 2 by the USB controller unit 418 via the USB connector 50. The USB controller unit 418 is also referred to as a data transfer unit.

  FIG. 4 is an overall flowchart of data conversion performed by the data input conversion device 1 according to the embodiment of the present invention. First, as an initial setting of the input data converter 1, CPU initial setting (S1), timer setting (S2), and hardware setting (S3) are performed. The CPU initial setting (S1) includes CPU clock setting, input / output pin setting, and memory area setting. In the timer setting (S2), the timeout time is set in the trigger mode in the case of high-speed sampling and in the case of low-speed sampling. In the hardware setting (S3), memory areas are allocated, a reference voltage is set for analog / digital conversion, and the like.

  After these initial settings, after initial setting of the USB transfer standard, a cable is connected to the USB connector (S4, S5). Next, the correction coefficient of the individual difference for each input data converter 1 is read (S6), and any one of steps S9 to S14, which are commands from the smartphone, is executed (S7 to S14).

  FIG. 5 is a flowchart of data processing in the auto mode. A sampling clock corresponding to the number of input channels is set (S91), and a sampling timer is started (S92). The analog data is converted into digital data by the sampling clock set in S91 and transferred to data memory access (DMA) (S93). Data acquisition is performed until the initially set number of data acquisitions reaches 2000. When the data acquisition reaches 2000, DMA transfer is stopped and measurement is terminated (S94 to S97).

  FIG. 6 is a flowchart of data processing in the trigger mode by the data input device 1. A sampling clock corresponding to the number of input channels is set (S101), a trigger level (threshold) is set, a trigger timeout is set, a trigger timeout timer is started, and measurement is started (S102 to S105).

  Analog data is AD converted at a sampling frequency corresponding to the number of input channels and transferred to the DMA (S106). This is repeated until the number of data reaches 2000, and 2000 data before trigger detection is transferred to the DMA (S107). In the present embodiment, since four-channel input is used, there are 500 input data for each channel.

  In the trigger mode, when the rising edge is to be measured, if the input data is smaller than the trigger voltage value (S109), the rising edge (maximum value) is waited (S110). The data is transferred to the DMA, this is performed until 2000 pieces of data are obtained (S111), and the measurement is terminated (S114). If the conditions in S109 and S110 are not obtained within the trigger timeout period, the measurement is terminated (S114). The rising edge is to measure a point at which the waveform starts to rise, and the falling edge is to measure the point at which the waveform starts to fall.

In the trigger mode, when the rising edge is to be measured, the input data is compared with the trigger voltage value. When the input data is smaller than the trigger voltage value (S109), the rising edge (maximum voltage value) is obtained. (S110), when the rising edge is detected, the data is transferred to the DMA, this is performed until 2000 pieces of data are obtained (S111), and the measurement is terminated (S114). If the conditions in S109 and S110 are not obtained within the trigger time-out time, the measurement ends at that time (S114).

  In the trigger mode, when it is desired to measure the falling edge, the input data is compared with the trigger voltage value. When the input data is larger than the trigger voltage value (S112), the falling edge (minimum voltage value) is When the falling edge is detected, the data is transferred to the DMA, this is performed until 2000 pieces of data are obtained (S111), and the measurement is terminated (S114). If the conditions in S109 and S110 are not obtained within the time of the trigger timeout, the measurement ends at that time (S114).

  FIG. 7 is a diagram illustrating an example of a method of operating the observation waveform displayed on the smartphone 2 using the touch panel of the smartphone. In a conventional oscilloscope, operations such as enlargement and reduction of a display waveform, setting of a reference voltage value, or comparison of waveforms of channel 1 and channel 2 are performed with a dial-type knob. However, according to one embodiment of the present invention, an operation as shown in FIG. 7 can be performed by an application using a touch panel of a smartphone. Thereby, operation can be performed more intuitively.

  FIG. 7A shows an operation method for moving up and down the observed Base 1 and Channel 2 Base lines (0 V). You can move the Base line by dragging the Base line of the channel you want to move. Further, when the trigger level (threshold value) is changed, the threshold value can be similarly changed by dragging up and down. Furthermore, the display portion can be enlarged or reduced by a flick operation.

  FIG. 7B is a diagram showing an operation when measuring the displayed waveform. In order to switch to the measurement mode (Measure Line), it is possible to switch to the measurement mode by long-pressing (LONG touch) the window in the upper left. For example, in order to measure the time between the X1 point of channel 1 and the X2 point of channel 2, the time can be known by dragging from X1 to X2. Similarly, for example, if it is desired to know the voltage from Y1 to Y2 of channel 2, the value can be obtained by dragging from Y1 to Y2. The display portion can be enlarged or reduced by a flick operation.

1 Input data conversion device 2 Smartphone 3 Probe 4 DUT 5 USB cable 10 Input connector 20 Impedance matching unit 30 Level shift unit 40 CPU
50 USB connector 51 Circuit power supply 410 AD conversion unit 411 Data memory access unit (DMA)
412 Sampling frequency adjustment unit 413 Trigger level detection unit 414 Control program unit 415 Trigger timeout timer 416 Level shift voltage 417 Correction value storage unit 418 USB controller unit

Claims (6)

A plurality of input channels that take in a plurality of analog input signals, an impedance matching unit that receives the analog input signals from the plurality of input channels, and performs impedance matching, and the impedance according to the number of input channels of the analog input signals A sampling frequency adjusting unit that adjusts a sampling frequency when digitizing each of the matched analog input signals into a digital sample;
An A / D converter that digitizes each of the analog input signals into digital samples at a sampling frequency defined by the sampling frequency adjustment unit;
A data memory access unit coupled to the plurality of A / D converters for storing the digital samples from the A / D converters;
An input data conversion device comprising: a data transfer unit that transfers a digital sample stored in the data memory access unit to a display device. 2. The input data according to claim 1, wherein the sampling frequency adjustment unit includes means for adjusting the sampling frequency of the N channel to A / N when the sampling frequency at the time of inputting one channel is A. 3. Conversion device. 3. The input data conversion according to claim 1, wherein the probe connected to the input channel is a probe having conductivity and capable of freely deforming the shape according to the shape of the device under test. apparatus.   A data display device connected to the input data conversion device according to claim 1, the probe according to claim 3, and the input data conversion device for processing data from the input data conversion device and displaying it graphically And a measuring device.   The measurement apparatus according to claim 4, wherein the data display device is a smartphone, and the input data conversion device is connected to the smartphone by USB (Universal Serial Bus) or wirelessly. A data display device connected to the input data conversion device according to claim 1, the probe according to claim 3, and the input data conversion device for processing data from the input data conversion device and displaying it graphically An oscilloscope characterized by comprising:

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