US4658651A
Expired / Lapsed
US
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Wheatstone bridge-type transducers with reduced thermal shift
Assignee: IMO Industries Inc
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Filing: 1985-05-13
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Granted: 1987-04-21
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Expires: 2005-05-13
Abstract
Abstract Thermal shift in Wheatstone bridge-type transducers is reduced by providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough. That diaphragm is supported in a mechanically floating condition, such as by interposing a cushion of compliant material between the diaphragm and a support which is subject to mechanical strains. An amount of unbalance required for balancing the strain gages on the diaphragm is determined. One of these strain gages is provided with a series balance equal to one-half of that determined amount, while an adjacent one of the strain gages is provided with a shunt balance equivalent to one-half of that determined amount. Alternatively, the strain gages are provided with an initial thermal zero shift offset requiring only a shunt balance for compensation, and thermal zero shift is then compensated only with that shunt balance, or the strain gages are provided with an initial thermal zero shift offset requiring only a series balance of compensation, and that thermal zero shift is then compensated with only that series balance.
Inventors
- 👤 Da Hong Le
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:36
CPC Classifications
G; G01; G01L; G01L19/00; G01L19/14; G01L19/145; G01L19/146; G01L1/00; G01L1/20; G01L1/22; G01L1/2287; G01L1/2293; G01L19/0007; G01L19/0038; G01L19/142; G01L19/143; G01L19/147; G01L9/00; G01L9/0041; G01L9/0051; G01L9/0052; G01L9/0054; G01L9/02; G01L9/06; G01L9/065; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49103
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
225 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages, while maintaining said uniform temperature coefficient of resistance; providing for said diaphragm a support subject to mechanical strains; providing a cushion of compliant material capable of isolating said diaphragm from said mechanical strains to which said support is subject; interposing said cushion of compliant material between said diaphragm and said support, when supporting said diaphragm in said housing with the aid of said support, while leaving said strain gages exposed to strains imposed by a physical parameter to be measured with said transducer; providing electric lead wires for said strain gages with sufficient limpness to prevent transmission of mechanical strains therealong; determining an amount of unbalance required of said strain gages for balancing a zero offset of said strain gages; providing one of said strain gages with a series balance equal to one-half of said determined amount; and completing balancing of said zero offset and also avoiding a thermal zero shift of the Wheatstone bridge by providing an adjacent one of said strain gages with a shunt balance equivalent to one-half of said determined amount.
Claim 2
Dependent Claim
225 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages, while maintaining said uniform temperature coefficient of resistance; providing for said diaphragm a support subject to mechanical strains; providing a cushion of compliant material capable of isolating said diaphragm from said mechanical strains to which said support is subject; interposing said cushion of compliant material between said diaphragm and said support, when supporting said diaphragm in said housing with the aid of said support, while leaving said strain gages exposed to strains imposed by a physical parameter to be measured with said transducer; providing electric lead wires for said strain gages with sufficient limpness to prevent transmission of mechanical strains therealong; determining an amount of unbalance required of said strain gages for balancing a zero offset of said strain gages; providing one of said strain gages with a series balance equal to one-half of said determined amount; and completing balancing of said zero offset and also avoiding a thermal zero shift of the Wheatstone bridge by providing an adjacent one of said strain gages with a shunt balance equivalent to one-half of said determined amount.
Claim 3
Dependent Claim
49 words
A method as claimed in claim 1, including the steps of: providing a wafer of said semiconductor material; determining a region in said wafer having a uniform temperature coefficient of resistance therethrough; and dissecting said region from said wafer to provide said diaphragm having said uniform temperature coefficient therethrough.
Claim 4
Dependent Claim
27 words
A method as claimed in claim 1, wherein: said cushion is made of an elastomer having a compliance sufficient to isolate said diaphragm from said mechanical strains.
Claim 5
Dependent Claim
28 words
A method as claimed in claim 1, wherein: said cushion is made of a silicone rubber having a compliance sufficient to isolate said diaphragm from said mechanical strains.
Claim 6
Dependent Claim
21 words
A method as claimed in claim 1, including the step of: covering said diaphragm and strain gages with electrically insulating gel.
Claim 7
Dependent Claim
22 words
A method as claimed in claim 5, wherein: a silicone gel is selected as said gel covering said diaphragm and strain gages.
Claim 8
Dependent Claim
27 words
A method as claimed in claim 5, including the step of: providing said cushion with a cavity conforming in shape to an overall configuration of said diaphragm.
Claim 9
Dependent Claim
83 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages with an initial zero offset and thermal zero shift requiring only a shunt balance for compensation; and compensating zero offset and thermal zero shift of said strain gages with only said shunt balance.
Claim 10
Dependent Claim
83 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages with an initial zero offset and thermal zero shift requiring only a shunt balance for compensation; and compensating zero offset and thermal zero shift of said strain gages with only said shunt balance.
Claim 11
Dependent Claim
22 words
A method as claimed in claim 8, including the step of: making both said initial zero offset and thermal zero shift positive.
Claim 12
Dependent Claim
22 words
A method as claimed in claim 8, including the step of: making both said initial zero offset and thermal zero shift negative.
Claim 13
Dependent Claim
80 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages with an initial zero offset and thermal zero shift requiring only a series balance for compensation; and compensating thermal zero shift of said strain gages with only said series balance.
Claim 14
Dependent Claim
80 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages with an initial zero offset and thermal zero shift requiring only a series balance for compensation; and compensating thermal zero shift of said strain gages with only said series balance.
Claim 15
Dependent Claim
37 words
A method as claimed in claim 11, including the steps of: making one of said initial zero offset and thermal zero shift positive; and making the other of said initial zero offset and thermal zero shift negative.
Claim 16
Dependent Claim
188 words
In a Wheatstone bridge type transducer having a housing, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages requiring a predetermined amount of unbalance for balancing a zero offset of said strain gages, and one of said strain gages having a series balance equal to one-half of said predetermined amount; a support for said diaphragm, subject to mechanical strains; means for isolating said diaphragm from said mechanical strains to which said support is subject, including a cushion of compliant material between said diaphragm and said support for supporting said diaphragm in said housing, while leaving said strain gages exposed to strains imposed by a physical parameter to be measured with said transducer; electric lead wires for said strain gages having sufficient limpness to prevent transmission of mechanical strains therealong; and means for completing balancing of said zero offset while also avoiding a thermal zero shift of the Wheatstone bridge, including a shunt balance equivalent to one-half of said predetermined amount, in an adjacent one of said strain gages.
Claim 17
Dependent Claim
188 words
In a Wheatstone bridge type transducer having a housing, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages requiring a predetermined amount of unbalance for balancing a zero offset of said strain gages, and one of said strain gages having a series balance equal to one-half of said predetermined amount; a support for said diaphragm, subject to mechanical strains; means for isolating said diaphragm from said mechanical strains to which said support is subject, including a cushion of compliant material between said diaphragm and said support for supporting said diaphragm in said housing, while leaving said strain gages exposed to strains imposed by a physical parameter to be measured with said transducer; electric lead wires for said strain gages having sufficient limpness to prevent transmission of mechanical strains therealong; and means for completing balancing of said zero offset while also avoiding a thermal zero shift of the Wheatstone bridge, including a shunt balance equivalent to one-half of said predetermined amount, in an adjacent one of said strain gages.
Claim 18
Dependent Claim
20 words
A transducer as claimed in claim 13, including: electrically insulating gel covering said diaphragm and strain gages in said housing.
Claim 19
Dependent Claim
25 words
A transducer as claimed in claim 13, wherein: said cushion comprises an elastomer having a compliance sufficient to isolate said diaphragm from said mechanical strains.
Claim 20
Dependent Claim
26 words
A transducer as claimed in claim 13, wherein: said cushion comprises a silicone rubber having a compliance sufficient to isolate said diaphragm from said mechanical strains.
Claim 21
Dependent Claim
20 words
A transducer as claimed in claim 14, wherein: said gel is a silicon gel covering said diaphragm and strain gages.
Claim 22
Dependent Claim
23 words
A transducer as claimed in claim 14, wherein: said cushion has a cavity conforming in shape to an overall configuration of said diaphragm.
Claim 23
Dependent Claim
131 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages and determining an amount of unbalance required for balancing a zero offset of said strain gages; supporting said diaphragm in a mechanically floating condition in said housing; providing one of said strain gages with a series balance equal to one-half of said determined amount; and completing balancing of said zero offset and avoiding also a thermal zero shift of said bridge by providing an adjacent one of said strain gages with a shunt balance equivalent to one-half of said determined amount.
Claim 24
Dependent Claim
131 words
In a method of making a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination the steps of: providing a diaphragm of semiconductor material accepting formation of strain gages therein having a uniform temperature coefficient of resistance therethrough; providing in said diaphragm strain gages and determining an amount of unbalance required for balancing a zero offset of said strain gages; supporting said diaphragm in a mechanically floating condition in said housing; providing one of said strain gages with a series balance equal to one-half of said determined amount; and completing balancing of said zero offset and avoiding also a thermal zero shift of said bridge by providing an adjacent one of said strain gages with a shunt balance equivalent to one-half of said determined amount.
Claim 25
Dependent Claim
69 words
In a Wheatstone bridge-type transducer, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficent of resistance therethrough, said strain gages having an initial zero offset and thermal zero shift requiring only a shunt balance for compensation; and means for compensating zero offset and thermal zero shift of said strain gages including only said shunt balance.
Claim 26
Dependent Claim
69 words
In a Wheatstone bridge-type transducer, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficent of resistance therethrough, said strain gages having an initial zero offset and thermal zero shift requiring only a shunt balance for compensation; and means for compensating zero offset and thermal zero shift of said strain gages including only said shunt balance.
Claim 27
Dependent Claim
69 words
In a Wheatstone bridge-type transducer, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages having an initial zero offset and thermal zero shift requiring only a series balance for compensation; and means for compensating zero offset and thermal zero shift of said strain gages including only said series balance.
Claim 28
Dependent Claim
69 words
In a Wheatstone bridge-type transducer, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages having an initial zero offset and thermal zero shift requiring only a series balance for compensation; and means for compensating zero offset and thermal zero shift of said strain gages including only said series balance.
Claim 29
Dependent Claim
121 words
In a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages requiring a predetermined amount of unbalance for balancing a zero offset of said strain gages; means for supporting said diaphragm in a mechanically floating condition in said housing; a series balance equal to one-half of said predetermined amount for one of said strain gages; and means for completing balancing of said zero offset while also avoiding a thermal zero shift of the Wheatstone bridge, including a shunt balance equivalent to one-half of said predetermined amount connected to an adjacent one of said strain gages.
Claim 30
Dependent Claim
121 words
In a Wheatstone bridge-type transducer having a housing, the improvement of reducing thermal shift, comprising in combination: a diaphragm of semiconductor material having strain gages therein and a uniform temperature coefficient of resistance therethrough, said strain gages requiring a predetermined amount of unbalance for balancing a zero offset of said strain gages; means for supporting said diaphragm in a mechanically floating condition in said housing; a series balance equal to one-half of said predetermined amount for one of said strain gages; and means for completing balancing of said zero offset while also avoiding a thermal zero shift of the Wheatstone bridge, including a shunt balance equivalent to one-half of said predetermined amount connected to an adjacent one of said strain gages.
References Cited (Backward Citations)
US4274423A
Cited
US4373397A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-04-20 | 1990-10-20 | 1991-04-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-20 | 1994-10-20 | 1995-04-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-20 | 1998-10-20 | 1999-04-21 | $7700.00 | Window Closed / Lapsed |