JPS61210966A - Highly accurate resistance measuring equipment - Google Patents

Abstract

PURPOSE:To facilitate the adjustment of a circuit by constituting the measuring terminal of a resistance measuring circuit so as to measure a resistance by switching two terminals to two super precise resistances per range with the aid of a relay contact and providing an arithmetic means for calculating the integrated conversion gain of an analog circuit for measuring a resistance value and a zero-point drift at every range. CONSTITUTION:A measuring device is so constituted to measure the resistance value by switching measuring terminals P1 and P2 to two super-precise resistances Rr1 and Rr2 per range with the aid of the relay contacts St1-St6 and SR1-SR4. For measurement the resistances Rr1 and Rr2 and a microcomputer MC 5 are used. It selects the resistances Rr1 and Rr2 in the middle of loading or unloading a laser trimming device, etc., calculates the zero-point of the analog circuit of the measuring device and the conversion gain with the aid of measurement data available from A/D-converting 2 the output of an arithmetic amplifier 1 in either case, the set data of a D/A converter 3 setting a target resistance value and the output state of a comparator 4, corrects and calculates the measured results of unknown resistances RX1-RX3 and decides the measured and resistance values.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laser trimming device that trims a part of a resistor of an electronic circuit such as a hybrid IC or a resistor to adjust it to a predetermined value, and a laser trimming device that trims a part of a resistor of an electronic circuit such as a hybrid IC or a resistor. This article relates to high-precision resistance measuring instruments used to measure and judge resistance, such as in-circuit testers that check body resistance.

2. Description of the Related Art As a conventional example, the principle diagram of a resistance measuring device used in a laser trimming device is shown in FIG. 5 An analog-to-digital converter (hereinafter referred to as A-D converter) that converts into a digital value D0, 3 is a resistor R to be laser trimmed.
Setting input data D corresponding to target resistance values of x1 to Rx3
A digital-to-analog converter (hereinafter abbreviated as DA converter) 4 converts I into an analog voltage v1, and 4 compares the voltages of V and V, and if the condition of vl>vo is satisfied, the laser of the main body of the laser trimming device is turned off. This is a voltage comparator that outputs a determination signal DC to stop light emission and end trimming.

R51~R113 Tov! 11~vI13ha each i warm i
It is a precision resistor and reference constant voltage source that is extremely stable in the surrounding environment such as II and has little change over time. Terminals for measuring Pl and Pl unknown resistance, SVl to SV3, and SS1 to 883 are relay contacts for selecting the resistance range of this measuring instrument.
Sx1 to F3x6 are relay contacts that determine which of the resistances to be measured is selected. For example, when Rx1 is selected, Sx1 and Sx4 are turned on.

Now, by using the measuring device configured as described above, convert it into a digital representation D0, input it to a microcomputer (not shown), etc., and register the known values of V, R, and so on.
The value of the unknown resistance value R1 can be calculated from equation (1). Also,
When simply determining whether the resistance to be measured R8 is larger or smaller than a predetermined value R, the judgment can be made by setting the DA converter so that the digital value D1 becomes the voltage vX shown in equation (2). An output D can be obtained.

Problems to be Solved by the Invention However, with the above configuration, if the error in determining whether the laser trimming exceeds the target value and in measuring the resistance value is to be highly accurate to 0.1% or less, it is difficult to meet the above-mentioned standard. In addition to the stability of the power supply and precision resistors, the operational amplifier 1. Zero point drift of voltage comparator 4 and A-D converter 2 and D-
Since the conversion gain of the A converter 3 and the drift of the zero point affect the accuracy, the condition is that the change in the surrounding environment of each of the circuit components is less than 0.01%. Therefore, it is necessary to carefully select the parts to be used, use only the best ones, and devise mounting techniques to reduce circuit drift, resulting in high costs and requiring periodic accuracy adjustments.

In view of the above-mentioned points, the present invention provides a high-precision resistance measuring instrument that limits high-performance components to only precision resistors and determines and measures resistance values at low cost and with high precision.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a plurality of ultra-precision resistors and a microcomputer, and in equipment such as laser trimming equipment and in-circuit testers, it can be used in a few seconds to several tens of seconds. During loading or unloading of the board, which is carried out at intervals of A device that calculates the zero point and conversion gain of the analog circuit of the measuring instrument based on the setting data of the D-A converter and the output state of the comparator, and performs measurement and judgment of resistance values by correcting and calculating the measurement results of unknown resistance. As described above, in the present invention, the microcomputer calculates the zero point and conversion gain of the analog circuit every short period of several seconds to several tens of seconds, so drifts in the zero point and gain of the measuring instrument can cause measurement errors. It is not accumulated as Additionally, the only component that requires high stability is the ultra-precision resistor.

Embodiment FIG. 1 shows an embodiment in which the resistance value measurement range is limited to a single range of 10KΩ to 10OKΩ in order to explain the principle of the present invention in an easy-to-understand manner. As in the conventional example, 1 is an operational amplifier, 2 is an A-D converter, 3 is a D-A converter, 4 is a voltage comparator, and 6 is a microcontroller equipped with input/output interface, memory, calculation, and judgment functions. It's a computer. Pl.

P is a measurement terminal, Rx1 to R. is the unknown resistance,
In this case, the range is from 10Ω to 100Ω.

Rrl and R72 are ultra-precision resistors whose resistance values hardly change (several ppm or less) due to aging, temperature, and humidity, and are 10.0OOKΩ, 1oo, and ooKΩ, respectively. R
, are ordinary (several tens to hundreds of ppm) precision resistances.

Sx1 to Sx6 and SR1 to SR4 are relay contacts,
This is for selecting one of Rx1 to Rx3 or R71°Rr2, and the microcomputer 5
controls SR1 to SR4. Sx1 to SI6 may be controlled by an external control device. v8 is a reference constant voltage source. Now, V, = -1(V), SR1 and SR2+7)
When the IJ relay contact is selected, v0=10(v) according to the above equation (1), and the value is A-D converted and input to the microcomputer 5. However, as mentioned above, the operational amplifier 1 and the A-D converter 2 have a zero point drift, and the values of V and R8 change due to changes in the surrounding environment and change over time. In reality, the output data DA of the A-D converter 2, which is equivalent to 1o(V), cannot be stably obtained for a long time. The output data of the A-D converter at this time is represented by D, the total zero point drift of operational amplifier 1 and A-D converter 2 is represented by ZA, the reference voltage V is represented, and the conversion gain including precision resistor R6 is represented by A. The following equation holds true between these.

p A 1= −+ Z A ・・・・・・・・・
...G3) Rrl Similarly, when Rr2 is selected, it is expressed by the following formula.

However, DA2 is the output data of the AD converter.

A solution is found from equations (3) and (4) with A and ZA as unknowns.

Now, when the value of the unknown resistance is R1, and if the output of the A-D converter 2 is DA, then the following equation holds true similarly to equation (3).

Therefore, R-work can be calculated using the above entry and the value of ZA. The microcomputer 6 outputs the value of H to the outside as measurement data R0.

Similarly, it is thought that the zero point and conversion gain of the voltage comparator 4 and the DA converter 3 change as well. Now, the input data DD of the D-A converter 3 is changed to D by the method described later.
Assuming that the input data DD1 is set such that the output of the voltage comparator 4 is OFF when Dl is OFF and ON when the output is D1+1, the operational amplifier 1, the voltage comparator 4, and the D-A converter 3 The total zero point drift is ZB, the D-A converter 3 and the reference voltage v,
.

If the conversion gain including precision resistor R8 is 'B, then Rrl
If you select , use the following formula (%). If , is selected, it is expressed by equation (9).

However, DD2 is the input data of the DA converter 3 at the boundary where the output of the voltage comparator 4 is ON-OFF when Rr2 is selected.

Similar to equations (5) and (6), when the solution is found using B and ZB as unknowns, the following is obtained.

Therefore, since B and ZD are known values, when the target resistance value R is given as setting data, the microcomputer 6 converts the input data DD of the DA converter 3 into the equation (
Calculate using the following equation (13) in which Rrl in 9) is replaced with R.

In the manner described above, the zero points and gain coefficients of all analog circuits of the measurement circuit of the present invention can be calculated.

Next, the operation of the microcomputer 5 to set the input data DD of the DA converter 3 to the value DDl or DD2 of the boundary state where the voltage comparator 4 turns ON-OFF will be explained with reference to the flowchart of FIG. In this embodiment, the DA converter 3 has a resolution of 16 bits. First, select the ultra-precision resistor Rr1 (step 1), then set the maximum value of the D-A converter 3 (hexadecimal FFFF) to the registers GA, GB, and Gc in the microcomputer 6.
), the minimum value 0, and the intermediate value (aooo in hexadecimal) are set (step 2). The value of Gc is sent to the DA converter 3.
(step 3), and after a certain period of time including the response time of the DA converter 3, the microcomputer 4 inputs the judgment output DC of the voltage comparator 4 (step 4.6). When the judgment output is ON, that is, when the input data Gc of the DA converter 3 is larger than the output of the operational amplifier 1, the value of the register GA is rewritten to the value of Gc, and the value GC of the input data of the DA converter is changed. (G(,+GB)/2 (Step 6).In the opposite case, set the value of register GB to G
c, and change the input data of the D-A converter to (Gc+
G A )/2 (step 7). If such an operation is repeated a maximum of 16 times, the values of GA, GB, and GC become equal with a difference of 1 digit or less (step 8), so the obtained value of Gc is defined as the value of DD1. Similarly, the value of DD2 turns off relays SR1 and SR2.
It can be determined by turning on L relays SR3 and SR4.

In the above explanation, the resistance measurement range is 10 to 10KΩ.
Although the explanation has been limited to a single range, for example, in a multi-range resistance measuring instrument with a measurement range of 1Ω to 100MΩ, two ultra-precision resistors are provided for each range using the same method. It is clear that the zero point drift and conversion gain can be calculated for each range.

A second embodiment of the invention is shown in FIG. In this example, a constant current I8 is used in the measurement circuit instead of a reference constant voltage source v8. 6 has a very large input impedance and a gain of 1.
This is a differential amplifier. The theoretical formula for the output voltage vp of the differential amplifier and the unknown resistance R is shown in formula (14).

V=IR・・・・・・・・・・・・・・・(14
)p 8N However, the zero point drift Zc1 that combines the differential amplifier 6 and the A-D converter 2, and the conversion gain C that includes the reference constant current source are subject to changes due to the surrounding environment and over time, as in the case of Fig. 1. There is a change. Therefore, if the output of the A-D converter when ultra-precision resistor Rr1 is selected is DAl, then DA1=CR, + ZC・・・・・・・・・・・・・・・
・(15), and as in the case of Fig. 1, ZC, C
The value of t - 0 that can be calculated by the microcomputer 6. Note that the relay contacts SR2 and SR4 can operate without them due to the circuit configuration, but the unknown resistances R and ~R are required.

Since two relay contacts are required for the circuit that selects the , these are provided to ensure that the effects of thermoelectromotive force and contact potential difference are the same.

As described above, the conversion gain and zero point of the measuring instrument are calculated for each range, but this operation, for example in laser trimming equipment or in-circuit testers, is performed when the board to be manufactured or inspected is loaded into the equipment. This is done by starting with a start signal Sc at a timing when the resistance measuring device is not measuring the unknown resistance, and returning a completion signal SE when the correction calculation is completed. Therefore, the stability of the internal parts of the measuring instrument may be within several seconds to several tens of seconds, which is the time required to measure or judge one board, and inexpensive parts can be used.

Effects of the Invention As described above, according to the present invention, the measurement terminal of the resistance measurement circuit is configured to be switched to two ultra-precise resistances per sill range using a relay contact, and the resistance measurement circuit is configured to be able to perform measurement by switching to two ultra-precise resistances for each sill range. By providing arithmetic means for calculating the total conversion gain and zero point drift of the analog circuit that determines whether it is high or low for each / ji, it is possible to reduce the cost of parts and implementation used in the circuit, and to improve the adjustment of the circuit. can be facilitated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a high-precision resistance measuring instrument according to the first embodiment of the present invention, FIG. 2 is a flowchart for bringing the input data of the digital-to-analog converter of the present invention into a boundary state, and FIG. A block diagram of a high-precision resistance measuring device according to a second embodiment of the present invention, and FIG. 4 is a block diagram of a conventional resistance measuring device. 1... operational amplifier, 2... analog
Digital converter, 3...Digital-to-analog converter, 4...Voltage comparator, 5...
・Microcomputer, 6...Differential amplifier,
v5...Reference constant voltage source, ■,...Reference constant current source, Rr4. Rr2...Super precision resistor, S
R1 to SR4...Relay contact, P4. P2...
...Measurement terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person
Fig. 4-m-Settlement 4-Non-ri-°-Jou 71 Compasshi-ta-Rzut4gN-°-Kin-dai-sun 8th edition Dingyou procedural amendment 1 Display of case 1985 Patent Application No. 53122 2. Name of the invention High-precision resistance measuring device 3. Relationship with the person making the amendment Patent application
Colonel Tokoro 1006 Kadoma, Kadoma City, Osaka Prefecture
(582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent 571 Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Correct to "Convert to voltage V". (2, page 3, lines 19-20, “To
Compare the voltages of V and V, and correct the condition of V,>Vo to the condition of V>v. (3) In the 10th page, line 18 of the same page, ``If selected, it will be expressed by formula (9)'' will be corrected to ``If selected, it will be expressed by formula (10).'' (4) On page 10, line 11 of the same page, ``If set, calculate amplifier 1'' should be corrected as follows. "If set, the output V of the operational amplifier 1 and the output v1 of the D-m converter 3 are equal. Therefore, the operational amplifier 1" ``In view of the above problems'' should be corrected to ``The present invention has been developed in view of the above problems.'' (7) Correct "Write the value of register G8 to Gc and write the value of register G8 to Gc" on the 2nd and 3rd lines of page 13. , D-m” to “register Gc
Write the value in GB and correct it to "D-person". (8) "Therefore, the stability of the parts inside the measuring instrument" in lines 7 and 8 of page 16 will be corrected to "therefore, the stability of the parts inside the measuring instrument." (9) Figures 1, 3, and 4 of the drawings will be corrected as shown in the attached sheet. ! -: 1JP4Wb each 2m-Analog counter L trace 11.3---Desi 7t afD gum 1 (each 4---Electric Li comparator JLt~5m, JRt~5R* -m-'' loop Tamimaro,
RLt-Kaichi Kioki resistance hole Figure 1 Vs-Toad 4tt, affiRs --
JIfrfihl also Rn, Rn---J! #Imay P1. Pt -Measurement fLS+ EU 2・-Application! L No. 3-□ Tenta I and 7 Derog Dog” Negative 4-tL Con/
Regulator 6-・Differential 411F4 J2. ~Eng ti, JRt-δ~・-Rishi 杞, Ehl,
Le t ・-・ Trend I capital mold resistance PbPz ・-, IFI large J + /-- 1 performance 4 width number 2 --- Analog ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛ ゛4-1. E Koshibaleta JV, -JVs, Jχr5m, 55t-55s ---
Relay contact, /? 5+~fat---Ken-table coffin IL kνφ-end left resistor 9 Figure 4 Vs+葡-11mm Pr, h---
Measurement pigeon Rx, 1

Claims (2)

[Claims] (1) Multiple ultra-precision resistors with two known and stable resistance values for each measurement range, a reference power supply that generates a constant voltage or current, and the current or voltage between the measurement terminals is amplified and converted to voltage. an analog/digital converter that converts the voltage of the amplifier into a digital value; and a first circuit that calculates a resistance value using a predetermined calculation formula from the output data of the analog/digital converter and outputs it as a digital value. calculation means, a relay for selecting one from the group of ultra-precision resistors and connecting it to the measurement terminal, and two of the analog-to-digital converters when two different ultra-precision resistors are connected for each range. A high-precision resistance measuring instrument comprising a second calculation means for calculating the conversion gain and zero point for each range using a predetermined calculation formula from two output data. (2) Multiple ultra-precision resistors with two known and stable resistance values for each measurement range, a reference power supply that generates a constant voltage or current, and the current or voltage between the measurement terminals is amplified and converted to voltage. a digital-analog converter that converts input data into an analog voltage; and a voltage comparator that compares the output voltage of the amplifier with the output voltage of the digital-analog converter and outputs an ON or OFF signal. , a first calculation means for calculating input data of the digital-to-analog converter using a predetermined calculation formula from a given resistance target value; A relay for connection and two different ultra-precision resistors for each range are connected, and in each state, the output of the voltage comparator is O.
detection means for finding the input data of the digital-to-analog converter that is in the N and OFF boundary states, and a calculation formula determined in advance from the two input data of the digital-to-analog converter in the boundary state for each range. A high-precision resistance measuring instrument comprising a conversion gain and a second calculation means for calculating a zero point.