ASTM F3291-17
(Test Method)Standard Test Method for Measuring the Force-Resistance of a Membrane Force Sensor (Withdrawn 2023)
Standard Test Method for Measuring the Force-Resistance of a Membrane Force Sensor (Withdrawn 2023)
SIGNIFICANCE AND USE
4.1 An MFS has similar properties to a load cell or strain gauge. However, an MFS is not suitable for precision measurements.
4.2 MFS pressure versus resistance data can be calculated if the force probe is providing uniform pressure over a distributed area or if the sensor is exposed to measurable air or hydraulic pressure.
4.3 MFS force-resistance plotted results are not linear and results may change when exposed to repeated force cycles – Test Method F1578. It is useful to note that the force-resistance curve models closely to mathematical form of y = 1/x.
4.4 Static forces may contribute to drifting test results (also known as creep).
SCOPE
1.1 This test method covers the force versus resistance measurement of a membrane force sensor (MFS) where the electrical resistance decreases as the force on the sensor is increased.
1.2 An MFS may or may not be electrically open in its static state. This depends on the attributes required for the application. If the MFS has a measureable resistance in static state, it was most likely designed to be used as a variable resistor, not as a normally open switch. A high but measurable resistance, in static state, may still be considered an open switch if the resistance is above the closed resistance threshold recognized by the interface electronics.
1.3 Special printed conductive polymer inks or characteristics, or both, of the sensor design are used in MFS to achieve variable resistance when compressed. As force is applied to the MFS the resistance continues to decrease, but not linearly, until a point where additional force does not change the resistance appreciably. Ideally, when force is removed from the MFS the resistance will return to, or close to, its original value.
1.4 Materials other than conductive polymers can be used in an MFS and also exhibit reduced resistance with increasing force.
1.5 This test method should not be confused with Test Method F2592 for measuring the force-displacement characteristics of a membrane switch (MS) that is designed for momentary closure. Although the resistance of a MS does change during contact closure the change from high resistance to contact resistance is very sudden and additional force does not have a significant effect on the resistance; that is, an MS is not designed to be used as a variable resistor.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
WITHDRAWN RATIONALE
This test method covers the force versus resistance measurement of a membrane force sensor (MFS) where the electrical resistance decreases as the force on the sensor is increased.
Formerly under the jurisdiction of Committee F01 on Electronics, this specification was withdrawn in November 2023. This standard is being withdrawn without replacement because Committee F01 was disbanded.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3291 − 17
Standard Test Method for
Measuring the Force-Resistance of a Membrane Force
1
Sensor
This standard is issued under the fixed designation F3291; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method covers the force versus resistance
1.7 This international standard was developed in accor-
measurement of a membrane force sensor (MFS) where the
dance with internationally recognized principles on standard-
electrical resistance decreases as the force on the sensor is
ization established in the Decision on Principles for the
increased.
Development of International Standards, Guides and Recom-
1.2 An MFS may or may not be electrically open in its static
mendations issued by the World Trade Organization Technical
state. This depends on the attributes required for the applica-
Barriers to Trade (TBT) Committee.
tion. If the MFS has a measureable resistance in static state, it
was most likely designed to be used as a variable resistor, not 2. Referenced Documents
as a normally open switch.Ahigh but measurable resistance, in
2.1 ASTM Standards:
static state, may still be considered an open switch if the
F2592 Test Method for Measuring the Force-Displacement
resistance is above the closed resistance threshold recognized
of a Membrane Switch
by the interface electronics.
F1578 Test Method for Contact Closure Cycling of a Mem-
1.3 Special printed conductive polymer inks or brane Switch
characteristics, or both, of the sensor design are used in MFS
3. Terminology
to achieve variable resistance when compressed. As force is
appliedtotheMFStheresistancecontinuestodecrease,butnot 3.1 Definitions:
linearly, until a point where additional force does not change
3.1.1 force at initial measurable resistance (Fim), n—force
the resistance appreciably. Ideally, when force is removed from at Rim. If there is a measurable resistance Rim at Fss then both
the MFS the resistance will return to, or close to, its original
Fss = Fim=0.
value.
3.1.2 initial measurable resistance (Rim), n—resistance of
1.4 Materials other than conductive polymers can be used in MFS without force applied (if measurable) or the first measur-
an MFS and also exhibit reduced resistance with increasing able resistance when test probe begins applying force.
force.
3.1.3 maximum sensor force (Fmaxs), n—a special maxi-
mum force to be applied to MFS during test or the force at
1.5 This test method should not be confused with Test
which no appreciable change in resistance is noted, also known
Method F2592 for measuring the force-displacement charac-
as saturation resistance.
teristics of a membrane switch (MS) that is designed for
momentary closure. Although the resistance of a MS does
3.1.4 maximum sensor pressure (Pmaxs), n—Fmaxs/surface
change during contact closure the change from high resistance
area of test probe in contact with MFS.
to contact resistance is very sudden and additional force does
3.1.5 membrane force sensor (MFS), n—similar in construc-
not have a significant effect on the resistance; that is, an MS is
tion to a non-tactile membrane switch (MS) but the measured
not designed to be used as a variable resistor.
resistance is designed to decrease as force applied is increased.
1.6 This standard does not purport to address all of the
Also sometimes referred to in the industry as a force sensing
safety concerns, if any, associated with its use. It is the
resistor.
responsibility of the user of this standard to establish appro-
3.1.6 membrane switch (MS), n—a momentary switching
device in which at least one contact is on, or made of, a flexible
substsrate.
1
This test method is under the jurisdiction of ASTM Committee F01 on
Electronics and is the direct responsibility of Subcommittee F01.18 on Printed
3.1.7 pressure at initial measurable resistance (Pim),
Electronics.
n—Fim/surface area of test probe in contact with MFS.
Current edition approved Nov. 1, 2017. Published November 2017. DOI:
10.1520/F3291-17 3.1.8 Rmaxs, n—resistance at Fmax.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
F3291 − 17
3.1.9 test probe tip diameter (Dtp), n—diameter of the test 7.2 In-Process Test:
probe tip (or actuato
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F3291 − 17
Standard Test Method for
Measuring the Force-Resistance of a Membrane Force
1
Sensor
This standard is issued under the fixed designation F3291; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This test method covers the force versus resistance
1.7 This international standard was developed in accor-
measurement of a membrane force sensor (MFS) where the
dance with internationally recognized principles on standard-
electrical resistance decreases as the force on the sensor is
ization established in the Decision on Principles for the
increased.
Development of International Standards, Guides and Recom-
1.2 An MFS may or may not be electrically open in its static
mendations issued by the World Trade Organization Technical
state. This depends on the attributes required for the applica-
Barriers to Trade (TBT) Committee.
tion. If the MFS has a measureable resistance in static state, it
was most likely designed to be used as a variable resistor, not 2. Referenced Documents
as a normally open switch. A high but measurable resistance, in
2.1 ASTM Standards:
static state, may still be considered an open switch if the
F2592 Test Method for Measuring the Force-Displacement
resistance is above the closed resistance threshold recognized
of a Membrane Switch
by the interface electronics.
F1578 Test Method for Contact Closure Cycling of a Mem-
1.3 Special printed conductive polymer inks or brane Switch
characteristics, or both, of the sensor design are used in MFS
3. Terminology
to achieve variable resistance when compressed. As force is
applied to the MFS the resistance continues to decrease, but not
3.1 Definitions:
linearly, until a point where additional force does not change 3.1.1 force at initial measurable resistance (Fim), n—force
the resistance appreciably. Ideally, when force is removed from
at Rim. If there is a measurable resistance Rim at Fss then both
the MFS the resistance will return to, or close to, its original
Fss = Fim = 0.
value.
3.1.2 initial measurable resistance (Rim), n—resistance of
1.4 Materials other than conductive polymers can be used in MFS without force applied (if measurable) or the first measur-
an MFS and also exhibit reduced resistance with increasing able resistance when test probe begins applying force.
force.
3.1.3 maximum sensor force (Fmaxs), n—a special maxi-
mum force to be applied to MFS during test or the force at
1.5 This test method should not be confused with Test
which no appreciable change in resistance is noted, also known
Method F2592 for measuring the force-displacement charac-
as saturation resistance.
teristics of a membrane switch (MS) that is designed for
momentary closure. Although the resistance of a MS does
3.1.4 maximum sensor pressure (Pmaxs), n—Fmaxs/surface
change during contact closure the change from high resistance
area of test probe in contact with MFS.
to contact resistance is very sudden and additional force does
3.1.5 membrane force sensor (MFS), n—similar in construc-
not have a significant effect on the resistance; that is, an MS is
tion to a non-tactile membrane switch (MS) but the measured
not designed to be used as a variable resistor.
resistance is designed to decrease as force applied is increased.
1.6 This standard does not purport to address all of the
Also sometimes referred to in the industry as a force sensing
safety concerns, if any, associated with its use. It is the
resistor.
responsibility of the user of this standard to establish appro-
3.1.6 membrane switch (MS), n—a momentary switching
device in which at least one contact is on, or made of, a flexible
substsrate.
1
This test method is under the jurisdiction of ASTM Committee F01 on
Electronics and is the direct responsibility of Subcommittee F01.18 on Printed
3.1.7 pressure at initial measurable resistance (Pim),
Electronics.
n—Fim/surface area of test probe in contact with MFS.
Current edition approved Nov. 1, 2017. Published November 2017. DOI:
10.1520/F3291-17 3.1.8 Rmaxs, n—resistance at Fmax.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
F3291 − 17
3.1.9 test probe tip diameter (Dtp), n—diameter of the test 7.2 In-Process Test:
probe tip (or actuator) that is in contact with MFS during test. 7.2.1 Record resistance if measurable at F0 – static state (if
not measurable resistance – rec
...
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