flexiforce vs shunt mode - tekscan.com · technology, universiti tun hussein onn malaysia, 86400...

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In this test, FlexiForce sensors delivered the same force output when step loaded with three different puck diameters, whereas two shunt mode sensor types showed inconsistent output. This data indicates that shunt mode sensor output is a funcon of both load area and applied force. SUMMARY F LEXI F ORCE VS S HUNT M ODE FORCE SENSING TECHNOLOGIES How Do They Compare On Key Performance Aspects? NOT ALL FORCE SENSORS ARE CREATED EQUAL! There are important aspects to consider before making your tacle force sensor investment. This graphic compares FlexiForce™ sensors (Thru Mode technology) against a similar tacle force sensor referred to as “Shunt Mode” technology. We will cover some specific differenang aspects between these two technologies that will be supported by verifiable, third-party data. While FlexiForce proved to be the beer alternave in these tests, every applicaon has its own unique challenges and may produce different results. Whether as a standard sensor or custom soluon, our team of expert engineers is standing by to find the right FlexiForce soluon to achieve your needs. See the full summary of data by visiting www.tekscan.com/shunt-comparison CHOOSE WISELY. ISO 9001 Compliant & 13485 Registered +1.617.464.4283 1.800.248.3669 | [email protected] | www.tekscan.com/flexiforce REFERENCES: 1 Sadun, A.S., et. al. “Force Sensing Resistor (FSR): A Brief Overview and the Low Cost Sensor for Acve Compliance Control.” (2016) Faculty of Engineering Technology, Universi Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. 2 Vecchi, F. et. al. “Experimental Evaluaon of Two Commercial Force Sensors for Applicaons in Biomechanics and Motor Control.” Advanced Robocs Technology and Systems Laboratory. Scuola Superiore di Sant’Anna via Carducci 40, 56127 Pisa, Italy. 3 Benbourenane, I. “Design of Nasal Endoscopy Simulator with Force Feedback” (2014) Human Movement and Balance Lab of the University of Pisburgh.) Shunt Mode Sensors Polymer thick-film devices consisting of two membranes separated by a thin air gap. Membrane 1 has two sets of interlaced traces electrically isolated from one another. Membrane 2 is coated with a special textured, resistive ink. When pressed, the ink shorts the traces together with a resistance that depends on the applied force. H ERE ' S W HAT W E ' RE W ORKING W ITH . SO, WHEN UNLOADED, R ESISTANCE I S HIGH — WHEN P RESSED, R ESISTANCE DROPS According to manufacturer specs, FlexiForce can capture a wider range of force with greater accuracy than a majority of Shunt Mode force sensing resistors. The force range of FlexiForce sensors can also be adjusted to match the needs of the applicaon. FlexiForce Sensors (AKA, “Thru Mode Technology,” or “Piezoresistive Technology”) Ultra-thin and flexible printed circuits consisting of two flexible substrates (polyester film). Silver circles with traces are positioned above and below a pressure-sensitive layer. This is the sensing area. Conductive polymer is applied on each layer, followed by a pressure sensitive layer. Adhesive is used to laminate the two layers of substrate. FlexiForce Sensors ~0 N - 444.8 N (0 lb - 100 lb) with some sensors reaching up to 44,482 N! Most Shunt Mode Sensors ~0.2 N - 20 N (0 lb - 5 lb) #4: DYNAMIC RANGE #5: SENSING AREA DEPENDENCE SUMMARY FlexiForce produced a more linear relaonship in the two calibraon tests. The Shunt Mode sensor appeared parcularly non-linear within the 0-4 N force ranges. #1: LINEARITY SUMMARY FlexiForce was less suscepble to driſt compared to the Shunt Mode sensor, whether loaded or placed into a controlled environment. #2: SENSOR DRIFT SUMMARY FlexiForce was significantly more accurate than Shunt Mode sensor at all three force ranges. #3: DYNAMIC MEASUREMENT ACCURACY SUMMARY FlexiForce Sensors (1) Shunt Mode Sensors (1) CALIBRATION TEST 0-4 N (1) CALIBRATION TEST 0-30 N (2) TIME DRIFT DUE TO A 15 N LOAD (2) 12-HOUR RESISTANCE DRIFT AT 3V (3) FlexiForce Shunt Mode Static calibration of FlexiForce and Shunt Mode sensors (with substrates) FlexiForce Shunt Mode In this test, the subject wearing a device equipped with either FlexiForce or Shunt Mode sensors pinched a strain gauge dynamometer varying the exertion force five times over a 10-second period. The total error at each force level was computed as the difference between the force measured using the dynamometer and the force obtained from the sensor output. REHABILITATION GRIP DEVICE TEST (2) FlexiForce Sensors Shunt Mode Sensors A FlexiForce A401 and an Shunt Mode sensor were placed in a tube for 12 hours. Voltage readings were recorded every minute. OUTPUTTED CONSTANT VOLTAGE DEGRADED TO 0V AFTER 5 HOURS 12 HR 12 HR 0V 0V 3V 3V Shunt Mode Output Voltage (V) Applied Force (N) FlexiForce Output Voltage (V) Applied Force (N) Percentage Error (%) 0 1 2 3 4 5 6 7 Average Error (N) (2) 0-20 N 0-25 N 0-30 N 2.7% 4.7% 3.6% 4.9% 4.6% 5.9% Percentage Error (%) 0 2 4 6 8 10 12 14 16 18 20 Maximum Error (N) (2) 0-20 N 0-25 N 0-30 N 7.4% 12.4% 9.9% 13% 14.2% 19.6% Percentage Error (%) 0 1 2 3 4 5 Standard Deviation (N) (2) 0-20 N 0-25 N 0-30 N 1.8% 3.1% 2.4% 3.7% 3.6% 4.4% FlexiForce Shunt Mode 100 lb 5 lb Normalized Output from the Sensors Force Applied to the Sensors (N) Percentage with Respect to the Initial Value Time (Minutes) 0.25 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.5 0.75 Voltage (V) Puck Diameter (inches) FlexiForce A401 Shunt Mode Sensor Brand 1 Shunt Mode Sensor Brand 2 Voltage Output at 5 lbs with Different Puck Diameters

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In this test, FlexiForce sensors delivered the same force output when step loaded with three different puck diameters, whereas two shunt mode sensor types showed inconsistent output. This data indicates that shunt mode sensor output is a function of both load area and applied force. SU

MMARY

FLEXIFORCE™ VS SHUNT MODEFORCE SENSING TECHNOLOGIES

How Do They Compare On Key Performance Aspects?

NOT ALL FORCE SENSORS ARE CREATED EQUAL!There are important aspects to consider before making your tactile force sensor investment.

This graphic compares FlexiForce™ sensors (Thru Mode technology) against a similar tactile force sensor referred to as“Shunt Mode” technology. We will cover some specific differentiating aspects between these two technologies that

will be supported by verifiable, third-party data.

While FlexiForce proved to be the better alternative in these tests, every application has its own unique challenges and may produce different results. Whether as a standard sensor or custom solution, our team of expert engineers is standing by to find the right FlexiForce solution to achieve your needs.

See the full summary of data by visiting

www.tekscan.com/shunt-comparison

CHOOSE WISELY.

ISO 9001 Compliant & 13485 Registered

+1 . 617. 4 6 4 . 4 2 8 3 1 . 8 0 0 . 2 4 8 . 3 6 6 9 | i n f o @ t e k s c a n . c o m | w w w. t e k s c a n . c o m / � e x i f o r c e

REFERENCES:1Sadun, A.S., et. al. “Force Sensing Resistor (FSR): A Brief Overview and the Low Cost Sensor for Active Compliance Control.” (2016) Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia.2Vecchi, F. et. al. “Experimental Evaluation of Two Commercial Force Sensors for Applications in Biomechanics and Motor Control.” Advanced Robotics Technology and Systems Laboratory. Scuola Superiore di Sant’Anna via Carducci 40, 56127 Pisa, Italy.3Benbourenane, I. “Design of Nasal Endoscopy Simulator with Force Feedback” (2014) Human Movement and Balance Lab of the University of Pittsburgh.)

Shunt Mode Sensors

Polymer thick-film devices consisting of two membranes separated by a thin air gap.

Membrane 1 has two sets of interlaced traces electrically isolated from one another.

Membrane 2 is coated with a special textured, resistive ink.

When pressed, the ink shorts the traces together with a resistance that depends on the applied force.

HERE'S WHAT WE'RE

WORKING WITH.SO,

WHEN UNLOADED, RESISTANCE IS HIGH — WHEN PRESSED, RESISTANCE DROPS

According to manufacturer specs, FlexiForce can capture a wider range of force with greater accuracy than a majority of Shunt Mode force sensing resistors. The force range of FlexiForce sensors can also be adjusted to match the needs of the application.

FlexiForce Sensors (AKA, “Thru Mode Technology,” or “Piezoresistive Technology”)

Ultra-thin and flexible printed circuits consisting of two flexible substrates (polyester film).

Silver circles with traces are positioned above and below a pressure-sensitivelayer. This is the sensing area.

Conductive polymer is applied on each layer, followed by a pressuresensitive layer. Adhesive is usedto laminate the two layers of substrate.

FlexiForce Sensors

~0 N - 444.8 N (0 lb - 100 lb)with some sensors reaching

up to 44,482 N!

Most Shunt Mode Sensors

~0.2 N - 20 N(0 lb - 5 lb)

#4: DYNAMIC RANGE

#5: SENSING AREA DEPENDENCE

SUMMAR

Y

FlexiForce produced a more linear relationship in the two calibration tests. The Shunt Mode sensor appeared particularly non-linear within the 0-4 N force ranges.

#1: LINEARITY

SUMMAR

Y

FlexiForce was less susceptible to drift compared to the Shunt Mode sensor, whether loaded or placed into a controlled environment.

#2: SENSOR DRIFT

SUMMAR

Y

FlexiForce was significantly more accurate than Shunt Mode sensor at all three force ranges.

#3: DYNAMIC MEASUREMENT ACCURACY

SUMMAR

Y

FlexiForce Sensors (1) Shunt Mode Sensors (1)

CALIBRATION TEST 0-4 N (1)

CALIBRATION TEST 0-30 N (2)

TIME DRIFT DUE TO A 15 N LOAD (2) 12-HOUR RESISTANCE DRIFT AT 3V (3)

FlexiForceShunt Mode

Static calibration of FlexiForce and Shunt Mode sensors (with substrates)

FlexiForceShunt Mode

In this test, the subject wearing a device equipped with either FlexiForce or Shunt Mode sensors pinched a strain gauge dynamometer varying the exertion force five times over a 10-second period. The total error at each force level was computed as the difference between the force measured using the dynamometer and the force obtained from the sensor output.

REHABILITATION GRIP DEVICE TEST (2)

FlexiForce Sensors Shunt Mode Sensors

A FlexiForce A401 and an Shunt Mode sensor were placed in a tube for 12 hours. Voltage readings were recorded every minute.

OUTPUTTEDCONSTANT

VOLTAGE

DEGRADEDTO 0V AFTER

5 HOURS

12 HR12 HR0V 0V

3V 3V

Shun

t Mod

e O

utpu

t Vol

tage

(V)

Applied Force (N)

Flex

iFor

ce O

utpu

t Vol

tage

(V)

Applied Force (N)

Per

cen

tage

Err

or

(%)

0

1

2

3

4

5

6

7

Average Error (N) (2)

0-20 N 0-25 N 0-30 N

2.7%

4.7%

3.6%

4.9% 4.6%

5.9%

Per

cen

tage

Err

or

(%)

0

2

4

6

8

10

12

14

16

18

20

Maximum Error (N) (2)

0-20 N 0-25 N 0-30 N

7.4%

12.4%

9.9%

13%14.2%

19.6%

Per

cen

tage

Err

or

(%)

0

1

2

3

4

5

Standard Deviation (N) (2)

0-20 N 0-25 N 0-30 N

1.8%

3.1%2.4%

3.7% 3.6%

4.4%

FlexiForce Shunt Mode

100 lb

5 lb

Nor

mal

ized

Out

put f

rom

the

Sens

ors

Force Applied to the Sensors (N)

Per

cent

age

wit

h R

espe

ct to

the

Init

ial V

alue

Time (Minutes)

0.25

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0.5 0.75

Vo

ltag

e (V

)

Puck Diameter (inches)

FlexiForce A401 Shunt Mode Sensor Brand 1 Shunt Mode Sensor Brand 2

Voltage Output at 5 lbs with Different Puck Diameters