JPH0375072B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for displaying the characteristics of elements such as transistors and diodes, and particularly for displaying element characteristics such as changes in element characteristics and variations in characteristics of a plurality of elements. Regarding display method.

[Conventional technology]

A curve tracer is a measuring instrument that measures elements such as transistors and diodes, and displays the first and second signals related to the element, such as the collector-emitter voltage signal and collector current signal of the transistor, on an X-Y display. are doing. Conventionally, when measuring simple changes in element characteristics over time, changes in characteristics due to the application of heat, or variations in multiple elements using such measuring instruments, each measurement result was recorded numerically and compared, or the results of each measurement were compared. The characteristic curves themselves were recorded by taking photographs and compared.

[Problem that the invention seeks to solve]

In the conventional method of measuring changes in device characteristics as described above, the measurer records each measurement and
After all measurements were completed, all records had to be judged comprehensively, which was troublesome.

[Means for solving problems]

The device characteristic display method of the present invention digitizes the first and second signals related to the device under test, and stores the first and second digitized signals at respective storage locations in the first area of the storage means. sequentially stored in
The first and second signals digitized for each second and subsequent measurements are sequentially stored in each storage location of the second area corresponding to each storage location of the first area of the storage means, and the second and subsequent measurements are The magnitude of only one of the first and second signals selected from among the stored contents of the corresponding storage locations of the first area and the second area is compared with each other, and the storage location of the second area is determined according to the comparison result. The stored contents of are transferred to the corresponding storage location in the first area, and the
The display shows the characteristics of the device under test.

[Effect]

According to the present invention, although the first and second signals are paired, the one that changes more significantly is selected from the first and second signals, and only the selected signal is compared in magnitude. Therefore, in the first area, the maximum and minimum signals of the selected signal through all measurements are stored, so if the X-Y display is performed based on the stored contents of this first area, the measured object will be displayed. Changes in signal characteristics can be easily determined. In addition, when transferring the storage contents of the second area to the first area according to the comparison result, not only the selected signal but also the paired first and second signals are transferred, so they are stored in the first area. The displayed content is the correct measurement value.

〔Example〕

While FIG. 1 shows a flowchart of a preferred embodiment of the invention, reference will first be made to FIG. 2 to describe an instrument, or curve tracer, which utilizes the invention. A central processing unit (CPU) 10, a read-only memory (ROM) 12, a random access memory (RAM) 14, and a keyboard 16 are connected to a bus (including control lines, data lines, and address lines) 18.
Connect to. The CPU 10 uses the RAM 14 as a temporary storage device and performs various controls based on programs stored in the ROM 12. The keyboard 16 operates as an input device for setting various measurement conditions. The floating power supply 20 is connected to the bus 18
It supplies a rectified sine wave voltage with an amplitude set according to information from the measuring terminal 22 and 24 between the measurement terminals 22 and 24, and is generally called a collector supply. Bias supply circuit 26 supplies a step signal to measurement terminal 28 in accordance with information from bus 18 . Second
In the figure, a transistor 30 is connected to these measurement terminals 22, 24, and 28 as an element to be measured. The measurement terminal 24 is grounded, and a current detection resistor 32 is connected between the ground and the floating power supply 20. Also, large value resistors 34 and 36 for voltage detection are connected in series between the terminals 22 and 24.
Current from bias supply circuit 26 (base current)
flows into circuit 26 via terminal 28, the base-emitter junction of transistor 30, terminal 24 and ground, and since the values of resistors 34 and 36 forming the voltage divider are large, only the collector current of transistor 30 is resistive. It flows through the vessel 32. Differential amplifier 38 outputs a voltage proportional to the potential difference across resistor 32, ie, the current flowing through resistor 32.

Sample and hold (S/H) circuits 40 and 4
2 is a strobe signal from the timing circuit 44 that outputs the first and second signals related to the device under test 30, that is, the output voltage (collector voltage) of the voltage dividers 34-36 and the output voltage (collector current) of the differential amplifier 38. to simultaneously sample and hold. Note that the operating frequency of this timing circuit 44 is controlled by information from the bus 18. An electronic switch 46 alternately selects the outputs of the S/H circuits 40 and 42, and selects between analog and digital (A/D) outputs.
D) feeding converter 48; These electronic switches 46 and A/D converters 48 are connected to the timing circuit 44.
The held voltages are alternately converted into digital signals until the next sampling operation of the S/H circuits 40 and 42. Circuits 40 to 48 are A/D
It becomes a means of conversion. The output signal of the A/D converter 48 is stored in the RAM 14 via the bus 18 and sent to the CPU 1.
0 performs processing according to the program in the ROM 12. The display control circuit 50 includes a digital-to-analog converter and the like, and displays the display information processed by the CPU 10 on a display 52 such as a CRT in an X-Y manner.

Next, a preferred embodiment of the present invention will be described along the flowchart of FIG. In this embodiment, the characteristics of the collector-emitter voltage V (CE) and the collector current I (C) of the transistor 30 change over time (or due to heating changes), and change from the curve 54 as shown in FIG. 3 (base voltage is constant). curve 58 via curve 56
, that is, in the I(C) direction. In addition, the RAM 14, which is a storage means, has a processing area (first area) and a capture area (second area), as shown in FIG.
area).

The following operations are controlled by the CPU 10 according to the program in the ROM 12. First, in step 60, the first data, that is, the points A0 to A9 of the curve 54 is
The V (X-axis) and I (Y-axis) values of are stored in the capture area of the RAM 14. In this case, 10 points are digitized and captured, but the number of points is
In consideration of the storage capacity of 14 and the output cycle of the floating power supply 20, an arbitrary number can be set by the timing circuit 44. However, it should be noted that the number of measurement points on each curve is equal. The X and Y values (XA0, YA0) of point A0 are at storage location 0 in the capture area
is stored, and the X and Y values of point A1 (XA1, YA1)
are stored in storage location 1 of the capture area, and the following are sequentially stored in the same manner. At step 62, the data in each memory location in the acquisition area is transferred to a corresponding memory location in the processing area. In this example, the storage content of storage location 0 in the capture area is MIN0 in the processing area,
The contents of memory location 1 are MAX1, and the contents of memory locations 2, 3, 4, 5, 6, 7, 8 and 9 are MIN2, MAX3, MIN4, MAX5, respectively.
MIN6, MAX7, MIN8 and MAX9. Note that MIN and MAX mean a minimum value and a maximum value, and in this embodiment, the minimum value is determined for even-numbered measurement points, and the maximum value is determined for even-numbered measurement points.

In step 64, points B0 to B9 of curve 56
Find the X and Y values of
Store in the capture area of RAM14. That is, the storage contents of the capture area are rewritten. Since the characteristics of transistor 30 vary in the I(C) direction, ie, in the Y-axis direction, only the Y values of each corresponding storage location in the acquisition area and processing area are compared in step 66. The storage contents of storage location 0 in the import area (XB0, YB0) are the same as the storage contents of the corresponding storage location in the processing area (XA0, YA0), so
MIN0 remains as is. Y value YB1 of storage location 1 in the import area is the Y value of the corresponding storage location in the processing area
Since it is larger than YA1, it is not only YB1, but XB1
and YB1 are both transferred to the corresponding storage location in the processing area, and (XB1, YB1) becomes MAX1. Since the Y value YB2 of storage location 2 in the capture area is larger than the Y-axis YA2 of the corresponding storage location in the processing area, no transfer is performed and MIN2 of the processing area remains (XA2, YA2). Below, similar comparisons and transfers according to the comparisons are performed, and in the processing area,
MAX3=(XB3, YB3), MIN4=(XA4, YA4),
MAX5=(XB5, YB5), MIN6=(XA6, YA6),
MAX7=(XB7, YB7), MIN8=(XA8, YA8),
and MAX9=(XB9, YB9).

In step 68, for all measurements,
It is determined whether the comparison and transfer have been completed. If the comparison and transfer have not been completed yet (NO), the process returns to step 64, and if the comparison and transfer have been completed (YES), the process proceeds to step 70. In the case of FIG. 3, since the curve 58 has not yet been measured, the process returns to step 64 and the values of the measurement points C1 to C9 of the curve 58 are acquired. When the process of step 68 is performed,
The contents of the processing area of RAM14 are MIN0 = (XA0,
YA0), MAX1=(XC1, YC1), MIN2=(XA2,
YA2), MAX3=(XC3, YC3), MIN4=(XA4,
YA4), MAX5=(XC5, YC5), MIN6=(XA6,
YA6), MAX7=(XC7, YC7), MIN8=(XA8,
YA8) and MAX9 = (XC9, YC9). When all measurements have been completed, the process advances to step 70 via step 68, and an X-Y display as shown in FIG. 5 is performed based on the contents stored in the processing area of the RAM 14. The display shown in FIG. 5 is performed by sequentially reading out the contents of each storage location in the processing area. Since this display shows the maximum and minimum values of the characteristics of the device under test, it is easy to judge how the characteristics change. In addition, in FIGS. 3 and 5, in order to simplify the explanation, only 10 points are processed in each measurement, so the display in FIG. 5 is rough.
In reality, many points, for example 1024 points, are processed, so the display in FIG.
The area surrounded by 8 will be filled in.

When the device under test is a transistor, the characteristic curve changes in the I (Y axis) direction as shown in Figure 3.
In an element such as a constant voltage diode, the voltage changes in the V (X-axis) direction as shown in FIG. This measurement connects the cathode and anode of the diode to terminals 22 and 2.
4 respectively. Further, although the processing by the CPU 10 is the same as that described above with reference to FIGS. 1 and 4, the comparison in step 66 is performed only for the X value of the data at each point.

In Figures 5 and 6, the minimum and maximum values were obtained alternately from each measurement point, but the processing area of the RAM 14 was set as shown in Figure 7, and the maximum and minimum values were obtained for each measurement point. Good too. In this case, the storage capacity of the processing area is twice that of the capture area. Further, in step 62, the first captured data is transferred as the minimum and maximum values of the storage location of the corresponding processing area. That is, in step 62, the maximum value and minimum value of each measurement point become the same. Furthermore, in step 66, a comparison must be made for both the maximum and minimum values at the corresponding measurement points.

Also, every two points, for example A0, A1, B0 in Figure 3,
Find the maximum and minimum values for each of B1, C0, and C2, and similarly find the maximum and minimum values for each of A2, A3, B2, B3, C2, and C3, and similarly find the maximum and minimum values. good. In this case, the storage contents of the processing area of the RAM 14 are the same as the capture area.

The functions of the CPU 14 operating as shown in FIG. 1 are shown in blocks as shown in FIG. That is,
a storage control means 80 that controls writing and transfer of data to the capture area and processing area of the RAM 14;
A comparison means 82 that compares the storage contents of the capture area and the processing area and supplies the comparison result to the storage control means 80 corresponds to the CPU 10. Note that the storage control means 80, depending on the output of the comparison means 82,
Selectively transfers the storage contents of the capture area of RAM 14 to the processing area. As described above, the first and second signals from the device under test (DUT) 30 are digitized by the A/D conversion means 84 and stored in the RAM 14.

〔Effect of the invention〕

As described above, according to the present invention, changes in a device to be measured can be easily determined, and variations in a plurality of devices, changes over time in device characteristics, or thermal changes can be easily measured.
In addition, in multiple measurements, the maximum and minimum are determined only for one of the first and second signal signals related to the element, and the combination of the first and second signal pairs is processed as is. The display reliably maintains the actual measured value. (For example, the X and Y values of points A and C in Figure 3 will not mix.)

[Brief explanation of drawings]

FIG. 1 is a flow chart for explaining a preferred embodiment of the present invention, FIG. 2 is a block diagram of a measuring instrument using the present invention, FIG. 3 is a characteristic curve diagram for explaining the present invention, and FIG. 4 is a flowchart for explaining a preferred embodiment of the present invention. 5 and 6 are characteristic curve diagrams for explaining the present invention, and FIG. 7 is a diagram showing the storage means used in another embodiment of the present invention. FIG. 8, which is a diagram showing the first area, is a book diagram showing the functions of the present invention. In the figure, 14 is a storage means.

Claims (1)

[Scope of Claims] 1. The storage locations in the first area of the storage means are sequentially designated as a storage location for maximum values and a storage location for minimum values, and the values of the first and second signals related to the device under test at the same time are stored at the same time. sequentially digitizing the first and second signals in series, sequentially storing values at the same point in time of the first and second signals digitized in the first time in each storage location of the first area of the storage means; For each subsequent measurement, the values of the digitized first and second signals at the same time are set as one set and are sequentially stored in each storage location of the second area corresponding to each storage location of the first area of the storage means. storing the magnitude of only the selected one of the first and second signals among the stored contents of the corresponding storage locations of the first area and the second area of the storage means for each measurement from the second time onward; The values of the first and second signals are sequentially compared with each other, and the values of the first and second signals stored in the storage location storing the signal with the larger comparison result are stored in the maximum value storage location of the first area of the storage means. At the same time, the values of the first and second signals stored in the storage location storing the smaller signal of the comparison result are stored in the minimum value storage location of the first area of the storage means, and the storage X- according to the values of the first and second signals stored in each storage location of the first area of the means.
A method for displaying device characteristics, characterized in that the characteristics of the device to be measured are displayed using a Y display.