GB2197488A - High temperature strain gauge arrangement - Google Patents
High temperature strain gauge arrangement Download PDFInfo
- Publication number
- GB2197488A GB2197488A GB08725882A GB8725882A GB2197488A GB 2197488 A GB2197488 A GB 2197488A GB 08725882 A GB08725882 A GB 08725882A GB 8725882 A GB8725882 A GB 8725882A GB 2197488 A GB2197488 A GB 2197488A
- Authority
- GB
- United Kingdom
- Prior art keywords
- strain
- pair
- leads
- responsive
- resistance
- Prior art date
- 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.)
- Granted
Links
- 230000001143 conditioned effect Effects 0.000 claims 1
- 206010037660 Pyrexia Diseases 0.000 description 2
- 229910052729 chemical element Inorganic materials 0.000 description 2
- 239000004568 cement Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2268—Arrangements for correcting or for compensating unwanted effects
- G01L1/2281—Arrangements for correcting or for compensating unwanted effects for temperature variations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Description
1 J 45 GB2197488A 1
SPECIFICATION
High temperature strain system DESCRIPTION
The invention relates to strain gauges and is concerned with strain gauges that are especially useful at high temperature.
To measure strain, it is known to fix a strain-responsive element, in the form of a thin metal grid, to the specimen in which strain is to be measured and deduce any strain which the specimen may experience from the corresponding changes of electrical resistance that occur in the strain gauge. At elevated temperatures it may be appropriate also to measure the temperature which the grid is experiencing and the present invention is especially appropriate for use at high tem- peratures.
According to the present invention, there is provided strain-responsive apparatus including a strain-responsive element connected to calculator means at a location remote from the element by which an indication of strain may be derived from the temperature and electrical resistance of the element, the element and the calculator means being connected together by two pairs of different leads, each pair being similar to the other, the ends at the element of at least one pair being connected together so that the pair of leads form a thermo-coupie, whilst two of the similar leads, of each pair, are connected across a voltage supply and the other two of the similar leads of each pairs are connected across a voltmeter of which resistance is greater than that of the element.
Knowledge of the temperature of the ele- ment, when in use to respond to strain, at the moment when its resistance is measured can facilitate a correction for any variation of resistance that results from temperature change, rather than strain. The element may, therefore, before use, be subjected to changes in temperature without being strained and the consequent variation in resistance be recorded. This calibration could be supplied to the calculator means so that a correction can be applied when the strain gauge is in use. Calculator means, such as data loggers, are known by which the readings of resistance changes, corrected according to the calibration, can be interpretated as measurements of strain.
A correction can also be applied for the -apparent strain- that results from any difference between the co-efficients of expansion of the element and the specification with which it is used. In effecting the calibration, the ele- ment can be fixed to the specimen, without strain being applied to the specimen, and both heated to the sort of temperatures at which it is desired to measure strain. The variation of resistance will then represent both the direct effects of heat on the element and the effect of heat on the difference between the expansion co-efficient of the element and the specimen. These effects can be discounted by the calculator means when the element is in use and subjected to strain.
Strain-responsive apparatus embodying the invention will now be described with reference to the accompanying diagram.
A strain-responsive element of known kind is illustrated at 1, extending between terminals 2 and 3. The element 1 is connected to calculator means in the form of a computer controlled data logger 4 by two pairs of leads, A & B. Both pairs are housed within a minerally insulated, high temperature sleeve. If the strain gauge is used as a boiler installation say, these leads may need to be long. The two pairs of leads are similar; each includes a lead A formed from a material different from that of which lead B is formed. At the terminals 2 and 3 the leads A and B are connected together so that each pair of leads forms a thermocouple. Only one pair need be used although it can be arranged that the calculator means switches between one thermocouple and the other to. detect should there be any conflict between their indications.
In the calculator means 4, one of the leads, A, of each pair is connected across a micro- voltmeter 5 of such high resistance that neglible current flows in the lead A, so that the effect of the resistance of the leads is minimal. The signals in the microvoitmeter 5 resultfrom the effect of the excitation supply 6 and, from the signals, the strain in the element 1 is deduced.
In use, the element is fixed, by a ceramic cement, spot welding, or otherwise, to the specimen (not shown) in which the strain is to be measured. The applied strain affects the resistance of the element 1, but resistance is also affected by its natural variation with temperature and by the strain, known as -apparent strain-, caused by the difference between the co-efficients of expansion of the element and the specimen. For this reason, before the element is used, it is fixed to a specimen that is not otherwise strained and taken through the temperatures to which the element is likely to be subjected. In this way, variations in resistance resulting from -apparent strainand variations directly related to temperature can be recorded and discounted by the calculator means when the element 1 is in use.
It will be realised that the temperature is measured as close to the strain-responsive element as possible. The measuring system has a very low thermal inertia and this can be important when hightemperature gradients to temperature transients are involved.
Claims (3)
1. Strain-responsive apparatus including a strain-responsive element connected to calcu- lator means at a location remote from the ele- 2 GB2197488A 2 ment by which an indication of strain may be derived from the temperature and electrical resistance of the element, the element and the calculator means being connected together by two pairs of different leads, each pair being similar to the other, the ends at the element of at least one pair being connected together so that the pair of leads form a thermo-coupie, whilst two of the similar leads of each pair are connected across a voltage supply and the other, two of the similar leads of each pair are connected across a voltmeter of which the resistance is greater than that of the element.
2. Strain-responsive apparatus as claimed in claim 1 in which the strain-responsive element has previously been calibrated without strain, and the calculator means is conditioned by the results of the calibration.
3. Strain-responsive apparatus as claimed in either of the preceding claims in which the calculator means includes a data logger.
Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP Further copies may be obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB868626386A GB8626386D0 (en) | 1986-11-05 | 1986-11-05 | Strain gauge system |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8725882D0 GB8725882D0 (en) | 1987-12-09 |
| GB2197488A true GB2197488A (en) | 1988-05-18 |
| GB2197488B GB2197488B (en) | 1990-03-21 |
Family
ID=10606810
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868626386A Pending GB8626386D0 (en) | 1986-11-05 | 1986-11-05 | Strain gauge system |
| GB8725882A Expired - Lifetime GB2197488B (en) | 1986-11-05 | 1987-11-04 | Improvements in or relating to strain gauges |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868626386A Pending GB8626386D0 (en) | 1986-11-05 | 1986-11-05 | Strain gauge system |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPH0781813B2 (en) |
| DE (1) | DE3738318A1 (en) |
| GB (2) | GB8626386D0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2245709A (en) * | 1990-06-30 | 1992-01-08 | Rolls Royce Plc | Dual readout temperature and strain sensor combinations |
-
1986
- 1986-11-05 GB GB868626386A patent/GB8626386D0/en active Pending
-
1987
- 1987-11-02 JP JP27588887A patent/JPH0781813B2/en not_active Expired - Lifetime
- 1987-11-04 GB GB8725882A patent/GB2197488B/en not_active Expired - Lifetime
- 1987-11-11 DE DE19873738318 patent/DE3738318A1/en not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2245709A (en) * | 1990-06-30 | 1992-01-08 | Rolls Royce Plc | Dual readout temperature and strain sensor combinations |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3738318A1 (en) | 1989-05-24 |
| GB8725882D0 (en) | 1987-12-09 |
| JPH0781813B2 (en) | 1995-09-06 |
| GB2197488B (en) | 1990-03-21 |
| GB8626386D0 (en) | 1986-12-03 |
| JPS6486001A (en) | 1989-03-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19951104 |