GB1569390A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1569390A – Voltmeters
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GB1569390A – Voltmeters
– Google Patents
Voltmeters

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Publication number
GB1569390A

GB1569390A
GB32167/77A
GB3216777A
GB1569390A
GB 1569390 A
GB1569390 A
GB 1569390A
GB 32167/77 A
GB32167/77 A
GB 32167/77A
GB 3216777 A
GB3216777 A
GB 3216777A
GB 1569390 A
GB1569390 A
GB 1569390A
Authority
GB
United Kingdom
Prior art keywords
amplifier
input
output
switching means
coupled
Prior art date
1976-09-03
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB32167/77A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

HP Inc

Original Assignee
Hewlett Packard Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-09-03
Filing date
1977-08-01
Publication date
1980-06-11

1977-08-01
Application filed by Hewlett Packard Co
filed
Critical
Hewlett Packard Co

1980-06-11
Publication of GB1569390A
publication
Critical
patent/GB1569390A/en

Status
Expired
legal-status
Critical
Current

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Classifications

G—PHYSICS

G01—MEASURING; TESTING

G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES

G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass

G01R35/005—Calibrating; Standards or reference devices, e.g. voltage or resistance standards, «golden» references

Description

PATENT SPECIFICATION
( 21) Application No 32167/77 Q 31) Convention Application 1 N ( 32) Filed 3 Sept 1976 in ( 33) United States of America ( 44) Complete Specification pi ( 51) INT CL 3 GOIR 15/00 ($ 2) Index at acceptance GIU BC ( 22) Filed 1 Aug 1977 No 720486 (US) iblished 11 June 1980 (KA 1 VAT Tlr Mf TP’CD ( 71) We, HEWLETT-PACKARD COMPANY, of 1501 Page Mill Road, Palo Alto, California 94304, United States of ncerica, a corporation organized and i S isting under the laws of the State of California, United States of America, do hereby declare the invention, for which we pay that a patent may be granted to us, and she method by which it is to be performed, to be particularly described in and by the
following statement:
This invention is concerned with improvements in or relating to voltmeters.
The calibration of voltmeters has 151 eviosly been accomplished by measuring | outputs obtained upon the application f two known reference voltages and adjusting the transfer function thereof.
yipically one of the reference voltages is tid nd and the other reference voltage is lccted so as to produce a near full scale ltput The drawback of this method is that separate full scale reference voltages are required for each voltage range, many Vaibration adjustments are required and Mrift’ requires periodic calibration to retain f accuracy Since reference voltages are inherently expensive, especially in the case # high voltage references, it is desirable to 3 calibrate a multirange voltmeter using less than a reference voltage for each range.
The present invention provides a voltmeter responsive to an input signal pcomprising: first and second amplifiers each living an input and an output and each having a substantially linear transfer characteristic between the input and output Ithereof; source means for supplying first, second and third reference voltages; 4 first switching means for selectively applying either the first of the second refere nce voltage to the input of said first amplifier; second switching means for selectively applying either the first reference voltage, the third reference oltage or the input signal to the input of agid second amplifier; analog-to-digital converter means having an input selectively coupled to the output of the first or second s amplifier and an output for generating a digital signal representative of a signal to the output thereof; means for selectively coupling the input of said first amplifier to the output of said second amplifier during the selective application of a reference signal by said second switching means; a memory having an input and an output with the input coupled to the output of said converter means for selectively storing signals applied to the input thereof representative of the application of the first and second reference voltages to said first amplifier and the first and third reference voltages to said second amplifier; and processor means responsive to the selectively stored contents of said memory and to the output of said second amplifier for producing an output representative of the amplitude of the input signal normalized to correct for the offset and gain errors in said second amplifier.
In an apparatus as set forth in the last preceding paragraph it is preferred that said second amplifier comprises: a first differential amplifier having negative and positive inputs and an output, the positive input being coupled to a source of first reference potential, a first resistor having a first terminal coupled to the negative input of the first differential amplifier, first switching means serially coupled between the output and the negative input of the first differential amplifier, second and third switching means, each with first terminals coupled to the output of the first differential amplifier, a second resistor serially coupled between the second terminals of the second and third switching means, a third resistor serially coupled between the second terminal of the first switching means and the second terminal of the second switching means; said first amplifier comprises a second differential amplifier having positive and negative inputs and an output, a sixth switching means serially coupled between the output and the negative input of the second differential amplifier, a fourth resistor with a first terminal coupled to the output of the second differential amplifier and a second ( 11) 1569 390 L 1 less 1 LAD 2 1 i 6 ‘1390 S/ v Z terminal thereof coupled to a first terminal of a fifth resistor, the second terminal of the fifth resistor coupled to the source of first reference potential, a seventh switching means coupled between the second terminal of the fourth resistor and the negative input of the second differential amplifier, eighth switching means coupled between the second terminal of the fourth resistor and the fourth resistor and the second terminal of the third switching means, and ninth switching means coupled between the second terminal of the second switching means and the negative input of the second differential amplifier; said means for selectively coupling the input of said first amplifier to the output of said second amplifier comprising fourth and fifth switching means having first terminals coupled together and second terminals coupled to the second terminals of the second and third, switching means, respectively, the first terminals further coupled to the positive input of said second differential amplifier; said first switching means further comprises means for selectively applying the input signal to the positive input of the second differential amplifier and said second switching means selectively applies signals to the second terminal of the first resistor.
The present invention further provides a method for auto-calibrating a voltmeter comprising first and second amplifiers each having an input and an output and a substantially linear transfer function therebetween, the method comprising the steps of, performed in selected sequence; applying a known first voltage to the input of the first amplifier; storing the output of the first amplifier responsive to the application of the known first voltage; applying a known second voltage to the input of the first amplifier; storing the output of the first amplifier responsive to the application of the known second voltage; coupling the input of the first amplifier to the output of the second amplifier; applying the known first voltage to the input of the second amplifier; storing the output of the first amplifier responsive to the application of the known first voltage, to the second amplifier; applying a known third voltage to the input of the second amplifier; storing the output of the first amplifier responsive to the application of the known third voltage to the second amplifier; applying an unknown voltage to the input of the second circuit element; generating a representation of the unknown voltage responsive to the output of the second amplifier during the application of the unknown voltage to the input thereof and further responsive to the stored outputs by logically normalizing the representation to correct for the linear transfer function of the second amplifier defined by the stored outputs and by the values of the known first, second and third voltages.
There now follows a detailed description which is to be read with reference to the accompanying drawings of a voltmeter and of a method of auto-calibrating a voltmeter according to the invention, which have been selected for description to illustrate the invention by way of example.
In the accompanying drawings:Figure 1 is a block diagram of the preferred embodiment of the present invention; Figure 2 is a circuit illustrating the prior art technique for calibrating a linear voltmeter; Figure 3 is a detailed schematic of the D.C preamplifier 10 illustrating especially the measurement of the input offset errors (-X,,) for the first three voltage ranges; Figure 4 is a detailed schematic of the operational attenuator 20 illustrating especially the measurement of the input offset errors (Xn) for the fourth and fifth voltage ranges; Figure 5 illustrates the gain error measurement for the third (IOV) range; Figure 6 illustrates the gain error measurement for the second (IV) range, Figure 7 illustrates the second offset error measurement for the second (IV) range; Figure 8 illustrates the gain error measurement for the fourth (O 1 OV) range; and Figure 9 illustrates an autocalibrating system.
Referring to Figure 1, a block diagram of the preferred embodiment of the present invention, a voltmeter is illustrated having five voltage ranges A first range ( IV) is achieved by closing relay K 1 and FET switch Ql l and selecting a gain of 100 from D.C Preamplifier 10 A second range (IV) is achieved by selecting a gain of 10 from D C Preamplifier 10.
A third range (IOV) is achieved by selecting a gain of I from D C.
Preamplifier 10 A fourth range ( 10 OV) is achieved by closing relay K 2 and selecting a gain of 0 1 from the Operational Attenuator by closing FET switch Q 16 and selecting a gain of 1 from the D C Preamplifier 10 A fifth range (IOOOV) is achieved by selecting a gain of 0 01 from the Operational Attenuator 20 and by closing FET switch Q 18 Note that the full scale voltage applied to the Analog-to-Digital (AID) Converter 30 is always -10 volts.
Note also that the reference voltage, VREF, can be applied to either the D C.
Preamplifier 10 by closing FET switch Q 17, or to Operational Attenuator 20 by closing relay K 3 and FET switch Q 9 A ground 1.569390 1,569,390 input can similarly be applied to D C.
Preamplifier 10 by closing FET switch Q 13, or to the Operational Attenuator 20 by closing relay K 3 and FET switch Q 10 and for the combined calibration of D C.
Preamplifier 10 in series with the Operational Attenuator 20 as will be discussed in detail below.
The prior art techniques for calibration of
X a linear voltmeter in the prior art is illustrated in Figure 2 The reading of meter V will be:
X’=(V,+Vo)G where Vo is the offset error of the voltmeter and G is the gain of the voltmeter If switch 52 is closed such that V,= 0, the reading of meter V will be:
Xo=Vo G.
( 2) If switch Sl is closed such that VI=VREF, the reading of meter V will be:
the input offset errors for the fourth and fifth ( 1 OOV and 1000 V) ranges are made with the input of Operational Attenuator 20 grounded through a 100 K ohm resistor by relay K 3 and FET switch Q 10 A separate measurement is made for each range The fourth range is selected by closing FET switches Q 22 and Q 18 The fifth range is selected by closing FET switches Q 21, and Q 16 These measurements will be referred to as X 10 o and X 10 o, Referring now to Figure 5, the gain error measurement for the third (IOV) range is made by applying the internal precision reference voltage, VREF, (+ 10 VDC) to the input of D C Preamplifier 10 through FET switch Q 17 This measurement will be referred to as X 10 RE% The calibration of the third (IOV) range is now determined by the relationship:
XIN X Tofn V 10 -V INX%, IN VREF X 10 REF-X 10 hi REFT own ( 5) XREF=(VREF+VO)G ( 3) Combining equations ( 1), ( 2) and ( 3) gives the transfer function of the voltmeter when switch 53 is closed:
VN=VREF XIN-XO ( 4) XREF-XO d where Xo, is the offset of the voltmeter with a grounded input and Xo d is the offset of the ltmeter in a configuration prior to application of the reference voltage VREF, in 0 this case Xo =Xo 0.
By utilizing a voltmeter comprising highly linear elements, and further comprising logic for computing the transfer functions of the elements when configured for the various voltage ranges from the transfer functions of convenient calibration configurations, five voltage ranges can be calibrated with only a single reference voltage and a single precision resistive divider.
Referring to Figure 3, a detailed schematic of the D C Preamplifier 10, the input offset error measurements (Xo n) for the first three voltage ranges are made with the input of the D C Preamplifier 10 :grounded through a 100 K ohm resistor by FET switch Q 13 A separate measurement is rmade for each range to include the respective configurations of FET switches i O 031, Q 32, Q 23 and Q 29 appropriate for each voltage range These measurements will subsequently be referred to as X Ao Xo n; and X 1 %o,,.
Referring to Figure 4, a detailed i 5 schematic of the Operational Attenuator 20, since for this configuration X n=X’0 o D.
Referring to Figure 6, the gain error measurement for the second (IV) range is made by applying the internal precision reference voltage, V,, (+ 10 VDC) to the precision ten-to-one divider ( 900 K/100 K) by closing FE Ts Q 25 and Q 20 The one volt output is applied to D C Preamplifier 10 by FET switch Q 16 the gain of the D C.
Preamplifier 10 is set to X 10 to give a full scale output This measurement will be referred to as XREF Referring to Figure 7, a second oflset error measurement is made on the I VDC range with the input of the D C.
Preamplifier 10 grounded through the precision ten-to-one divider by FET switch Q 16 This measurement is made to include offset errors which may be present during the gain error measurement and will be subsequently referred to as X 1 O, D The calibration of the second ( 1 VDC) range is therefore determined by the relationship:
V 1 INXVINXO 10 XR REF-X 1 ED XREFX o D ( 6) A separate gain error is not made for the first ( I VDC) range since only difference between the circuit configuration of the 1 VDC range and the 1 VDC range is a precise gain of ten as determined by the precision ten-to-one divider The calibration for the first range thus becomes:
XIN-X 01 o n V IN VEF,100 X’REF-X 10 O ( 7) ,, 1,569,390 Referring to Figure 8, for the 100 VDC range gain error measurement the internal precision voltage reference ( 10 VDC) is applied to the input of Operational Attenuator 20 through FET switch Q 9 and relay K 3 The attenuator gain is set to 0 1 by FET switch Q 22 The output of the Operational Attenuator 20 is applied to the input of the D C Preamplifier 10 by FET switch Q 18 The D C Preamplifier 10 is set to a gain of 10 to provide a 10 VDC fullscale output This measurement will subsequently be referred to as X 10 %REF A second offset measurement is made on the 100 VDC range to include offsets which may be present during the reference voltage measurement This measurement is identical to the measurement of X 1 % 0, described above and illustrated in Figure 4 except that the D C Preamplifier 10 gain is set to X’ This measurement will be subsequently referred to as X 1 O, Since the full-scale measurement was made with an X 10 D C Preamplifier 10 gain configuration and an Xl D C Preamplifier gain configuration is used in the 100 VDC range, the transfer function is corrected by dividing by the XIO gain and multiplying by the Xl gain The calibration for the fourth ( 100 VDC) range therefore is determined by the relationship:
V IN=l OVREF ( 8) x 100rx 1 Oa XREFX X REP-X o D X 10 -X 10, X FEF-Xo f A separate gain error measurement is not required for the 1000 VDC range Since the only difference between the 100 VDC and the 1000 VDC gain errors is a precise attenuation of 10 resulting from the precision ten-to-one divider The calibration for the 1000 VDC range therefore becomes:
XIN-X V O IN= l OVREF ( 9) Y 100 _E YX 100.
Sx REF _X o D X REF-X 00 X 1 R Er-X 100 O Figure 9 shows the autocalibrating system The input voltage and the reference voltages are selectively applied to the input of a selected configuration of circuit elements SC A detector 10, responsive to the output of the selected configuration, SC, loads selected outputs into a memory M.
These selected outputs define the transfer function of the selected configuration and can be logically combined with other transfer functions to determine the transfer function of selected configurations not 55 directly measured A processor, P, then combines the appropriate transfer function with the detected output when an unknown input voltage is applied and provides an output normalized for the transfer function 60 of the configuration of circuit elements used for the measurement.
The objects of the present invention have been accomplished by the use of only two precision elements, a precise internal 10 65 VDC reference and a precise resistive divider, By having the processor periodically sample the correction factors during measurements and applying the corrective transfer functions to the output 70 obtained from a measurement of an unknown voltage, an extremely accurate mode of voltage determination is accomplished, which constantly corrects for drifting components and requires a 75 minimum amount of operator intervention for calibration.

Claims (4)

WHAT WE CLAIM IS:

1 A voltmeter responsive to an input signal comprising: 8 C first and second amplifiers each having an input and an output and each having a substantially linear transfer characteristic between the input and output thereof; source means for supplying first, second 85 and third reference voltages; first switching means for selectively applying either the first or the’ second reference voltage to the input of said first amplifier; 9 C second switching means for selectively applying either the first reference voltage, the third reference voltage or the input signal to the input of said second amplifier; analog to digital converter means having 95 an input selectively coupled to the output of the first or second amplifier and an output for generating a digital signal representative of a signal applied to the input thereof; means for selectively coupling the input 100 of said first amplifier to the output of said second amplifier during the selective application of a reference signal by said second switching means; a memory having an input and an output 105 with the input coupled to the output of said converter means for selectively storing signals applied to the input thereof representative of the application of the first and second reference voltages to said first 110 amplifier and the first and third reference voltages to said second amplifier; and processor means responsive to the selectively stored contents of said memory and to the output of said second amplifier for producing an output representative of the amplitude of the input signal normalized to correct for the offset and gain errors in said second amplifier.

2 A voltmeter according to claim 1, wherein said second amplifier comprises: a first differential amplifier having negative and positive inputs and an output, the positive input coupled to a source of first reference potential, a first resistor having a first terminal coupled to the negative input of the first differential amplifier, first switching means serially coupled between the output and the negative input of the first differential amplifier, second and third switching means, each with first terminals coupled to the output of the first differential amplifier, a second resistor serially coupled between the second terminals of the second and third switching means, a third resistor serially coupled between the second terminal of the first switching means and the second terminal of the second switching means.
said first amplifier comprises a second differential amplifier having positive and negative inputs and an output, a sixth switching means serially coupled between the output and the negative input of the second differential amplifier, a fourth resistor with a first terminal coupled to the output of the second differential amplifier and a second terminal thereof coupled to a first terminal of the fifth resistor, the second terminal of the fifth resistor coupled to the source of first reference potential, a seventh switching means coupled between the second terminal of the fourth resistor and the negative input of the second differential amplifier, eighth switching means coupled between the second terminal of the fourth resistor and the fourth resistor and the second terminal of the third switching means, and ninth switching means coupled between the second terminal of the second switching means and the negative input of the second differential amplifier; said means for selectively coupling the input of said first amplifier to the output of said second amplifier comprising fourth and fifth switching means having first terminals coupled together and second terminals coupled to the second terminals of the second and third switching means, respectively, the first terminals further coupled to the positive input of the second differential amplifier; said first switching means further comprises means for selectively applying the input signal to the positive input of the second differential amplifier and said second switching means selectively applies signal to the second terminal of the first resistor.

3 A voltmeter substantially as hereinbefore described with reference to the accompanying drawings.

4 A method for auto-calibrating a voltmeter comprising first and second 70 amplifiers, each having an input and an output and a substantially linear transfer function therebetween, the method comprising the steps of, performed in selected sequerfce; 75 applying a known first voltage to the input of the first amplifier; storing the output of the first amplifier responsive to the application of the known first voltage; 80 applying a known second voltage to the input of the first amplifier; storing the output of the first amplifier responsive to the application of the known second voltage; 85 coupling the input of the first amplifier to the output of the second amplifier; applying the known first voltage to the input of the second amplifier; storing the output of the first amplifier 90 responsive to the application of the known first voltage to the second amplifier; applying a known third voltage to the input of the second amplifier; storing the output of the first amplifier 95 responsive to the application of the known third voltage to the second amplifier; applying an unknown voltage to the input of the second circuit element; generating a representation of the 100 unknown voltage responsive to the output of the second amplifier during the application of the unknown voltage to the input thereof and further responsive to the stored outputs by logically normalizing the 105 representation to the correct for the linear transfer function of the second amplifier defined by the stored outputs and by the values of the known first, second and third voltages 110 A method for auto-calibrating a voltmeter comprising first and second amplifiers, each having an input and an output and a substantially lifear transfer function therebetween, substantially as hereinbefore described with reference to the accompanying drawings.
ERIC POTTER & CLARKSON, Chartered Patent Agents, 5, Market Way, Broad Street, Reading RGI 2 BN, Berkshire.
Printed for Her Majesty’s Stationery Office, by the Courier Press Leamington Spa 1980 Published by The Patent Office, 25 Southampton Buildings London WC 2 A IAY, from which copies may be obtained.
1,569,390

GB32167/77A
1976-09-03
1977-08-01
Voltmeters

Expired

GB1569390A
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

US05/720,486

US4127811A
(en)

1976-09-03
1976-09-03
Auto-calibrating voltmeter

Publications (1)

Publication Number
Publication Date

GB1569390A
true

GB1569390A
(en)

1980-06-11

Family
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Application Number
Title
Priority Date
Filing Date

GB32167/77A
Expired

GB1569390A
(en)

1976-09-03
1977-08-01
Voltmeters

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US
(1)

US4127811A
(en)

JP
(1)

JPS5331178A
(en)

DE
(1)

DE2739529C3
(en)

GB
(1)

GB1569390A
(en)

Cited By (1)

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Publication number
Priority date
Publication date
Assignee
Title

GB2170012A
(en)

1985-01-23
1986-07-23
E M Electronics Limited
Voltage measurement

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US4337517A
(en)

1976-09-16
1982-06-29
Systron Donner Corporation
Method of automatically calibrating a microprocessor controlled digital multimeter

JPH0711542B2
(en)

1982-07-31
1995-02-08
キヤノン株式会社

Power consumption measuring device

US4541065A
(en)

1982-09-14
1985-09-10
John Fluke Mfg. Co., Inc.
Direct volts calibrator

JPH0697256B2
(en)

1986-04-14
1994-11-30
株式会社アドバンテスト

AC level calibration device

DE4439707A1
(en)

1994-11-05
1996-05-09
Bosch Gmbh Robert

Voltage reference with testing and self-calibration

DE59606645D1
(en)

1995-12-05
2001-04-26
Siemens Ag

ELECTRONIC MEASURING DEVICE

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(en)

2020-04-28
2023-01-06
레이크 쇼어 크라이오트로닉스 인코포레이티드

Ranging Systems and Methods for Reducing Transient Effects in Multi-Range Material Measurements

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(en)

2022-04-07
2022-07-12
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Non-contact three-phase voltage measuring system and method

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(en)

1967-11-01
1970-04-28
Bell Telephone Labor Inc
High impedance,self-zeroing,dc voltmeter circuit

US3566265A
(en)

1968-11-18
1971-02-23
Time Systems Corp
Compensated step ramp digital voltmeter

JPS5125162A
(en)

1974-08-26
1976-03-01
Yokogawa Electric Works Ltd

DENATSUSOKUTE ISOCHI

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(en)

1976-08-16
1977-08-09
The Sippican Corporation
Calibrating a measurement system including bridge circuit

1976

1976-09-03
US
US05/720,486
patent/US4127811A/en
not_active
Expired – Lifetime

1977

1977-08-01
GB
GB32167/77A
patent/GB1569390A/en
not_active
Expired

1977-08-18
JP
JP9909077A
patent/JPS5331178A/en
active
Pending

1977-09-02
DE
DE2739529A
patent/DE2739529C3/en
not_active
Expired

Cited By (1)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

GB2170012A
(en)

1985-01-23
1986-07-23
E M Electronics Limited
Voltage measurement

Also Published As

Publication number
Publication date

JPS5331178A
(en)

1978-03-24

DE2739529C3
(en)

1980-09-25

DE2739529A1
(en)

1978-03-09

DE2739529B2
(en)

1980-01-31

US4127811A
(en)

1978-11-28

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