Sensors

Flexiforce Sensors

Frequently Asked Questions

GENERAL OVERVIEW
What are some applications in which the FlexiForce® sensors have been used?
Does Images give educational discounts?
What is your return policy?
SENSOR OVERVIEW
Of what material is the FlexiForce sensor made?
Are FlexiForce sensors available in different shapes, lengths or sizes?
What is the resolution of the A201 sensor?
How does the sensor react to force? Is the resistance constant, or is it decreasing with a constant value?
How much can I overload the sensor without damaging it?
What is the lifetime of a FlexiForce sensor?
What materials/conditions could damage the sensor?
Can I fold the sensor?
Can I adhere the sensor to a surface?
How can I measure forces greater than 100 lbs?
What drive voltages can I apply to the sensor?
Why do I need an excitation circuit to read force with FlexiForce A201 sensors?
Does the resistive element react similar to a semiconductor (diode, etc.) that varies conductance with applied voltage?
What is the resistance range of the sensor?
How do I connect the sensor after it has been trimmed?
CONDITIONING AND CALIBRATION
Why do you need to condition the FlexiForce sensor?
How much error is induced if the sensor is not conditioned?
What is the maximum period of not using the sensor before you have to recondition it?
What is the reason for calibrating the sensor?
How long must the sensor be unloaded before you load it again?
Is "110% of the maximum load" what the sensor can handle?
USING A PUCK OR SHIM
What is a puck/shim and do I need to use it?
What material is best to use?
How rough can the load surface be?
What surface is best to use underneath the sensor?
ELFTM SYSTEM AND CALIBRATION
Why do I need to calibrate the sensor?
What is the resolution of the ELF system?
What is the maximum speed of the ELF system?
Can I use more than one sensor at a time?
ENVIRONMENTAL
Are the FlexiForce sensors waterproof?
What are the influences of humidity on the sensor?
Can the sensors pick up electrical noise?
What are the influences of magnetic fields or radiation?
CUSTOMIZATION OF FLEXIFORCE SENSORS
What is the smallest active sensing area you can make?
What is the maximum force range that you can make?
What is the usual turn-around time for custom designs?
What are the minimum and maximum quantities you can do annually?
Can you make custom sensors that work with the ELF System?
What is the average cost of a custom design?
How can you find us?



What are some applications in which the FlexiForce sensors have been used?

FlexiForce sensors provide economical solutions and OEM tools to a variety of force measurement applications. Our sensors have been integrated into drug delivery devices, QA/QC equipment, industrial controls, sports and recreational gear, and more. The applications are endless and the list continues to grow.
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Does Images give educational discounts?

We give large-quantity price breaks only, due to the reasonable prices of our FlexiForce products.
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What is your return policy?

Package must be returned unopened within 48 hours of receipt of merchandise.
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Of what material is the FlexiForce sensor made?

The outer material is polyester (a brand name would be Mylar), the conductive traces are silver, and proprietary resistive inks are used within the sensing area.
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Are FlexiForce sensors available in different shapes, lengths or sizes?

The standard FlexiForce sensor is one shape, but can be trimmed to any length. We do offer a custom sensor design and manufacturing service. To request more information on custom sensor design, refer to the custom sensor page.
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What is the resolution of the A201 sensor?

The sensor will produce an analog signal and the resolution depends upon the electronics used.
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How does the sensor react to force? Is the resistance constant, or is it decreasing with a constant value?

The inks in our sensors are resistive: the greater the force, the less the resistance. To learn more, refer to the sensor performance graph.
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How much can I overload the sensor without damaging it?

The mechanical properties of the different force range sensors are very similar. The polymer materials from which these sensors are manufactured will start to deform plastically around 10,000 PSI.
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What is the lifetime of a FlexiForce sensor?

The durability of the FlexiForce sensor depends on the conditions to which it is exposed: magnitude of the load, the interface material, and the direction of the load (minimal shear). The sensor was tested under "normal" conditions with a 50LB impact load on the sensor, which was between two pieces of metal. 1,000,000 cycles/hits were achieved. Upon completion of the tests, the sensor's output still varied with applied load.
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What materials/conditions could damage the sensor?

Temperatures >155°F, water-submersion (as the adhesive holding the top & bottom layers together would likely separate), sharp objects, shear forces, creasing the sensor, and loads that are around or above 10,000PSI can damage the sensor. Refer to FlexiForce Specifications for sensor performance details.
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Can I fold the sensor?

The sensor is designed to be flexible, however the sensing area should not be folded as this causes shearing. The traces should not be bent more than 90° as the silver conductive leads could break.
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Can I adhere the sensor to a surface?

If you need to adhere the sensor to a surface, a thin, double-sided tape is recommended. It is best to apply tape to the shaft of the sensor rather than underneath the sensing area. An adhesive (glue) can be used if it will dry evenly.
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How can I measure forces greater than 100 lbs?

In order to measure forces above 100 lbs. (up to 1000 lbs.), apply a lower drive voltage and reduce the resistance of the feedback resistor (1kV min.) The force ranges of the sensors are based on our electronics. Please refer to .
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What drive voltages can I apply to the sensor?

0.1V (as long as signal-to-noise (S/N) ratio remains acceptable) to 18V is the typical range. The sensors output is also a function of the drive voltage/current therefore a constant voltage is recommended (see resistive element question below).
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Why do I need an excitation circuit to read force with FlexiForce A201 sensors?

You should use an excitation circuit to provide a constant drive voltage/current and provide an output voltage that is proportional to the applied force.
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Does the resistive element react similar to a semiconductor (diode, etc.) that varies conductance with applied voltage?

Yes.
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What is the resistance range of the sensor?

The resistance range of the sensor is typically from >5M at no load to approximately 5k at full load. This can vary depending on the electronics being used to drive and read the sensor.
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How do I connect the sensor after it has been trimmed?

If Images trims the A201 sensors to two inches, four inches, or six inches, the sensor will come with three (3) male square pin connectors spaced at 0.1" (2.54mm). If you trim the sensor yourself, you will need to re-connect the sensor using one of two methods. You can purchase staked pin connectors and a crimping tool, or you can use a conductive epoxy to adhere small wires to each conductor.
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Why do you need to condition the FlexiForce sensor?

You should always condition the sensor prior to testing because the sensor's output changes the first few times it is loaded. By loading the sensor before your calibration, you will ensure that the sensor is producing repeatable results for your calibration and testing. It will also produce a repeatable drift curve. You can condition the sensor by loading it at 110% of your maximum load for a few cycles.
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How much error is induced if the sensor is not conditioned?

The error could be greater than the standard ± 5% error if not conditioned prior to testing. You should always condition the sensor prior to use.
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What is the maximum period of not using the sensor before you have to recondition it?

You should recondition the sensor if you haven't used it in several weeks. Please note that the more you recondition it, the better it should perform.
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Why do I need to calibrate the sensor?

Calibration is a very important step. There is a slight variance between sensors, which calibration corrects. When performed in an environment similar to that of the test environment, calibration helps improve repeatability and neutralize drift.
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How long must the sensor be unloaded before you load it again?

There is no exact or estimated time.
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Is "110% of the maximum load" what the sensor can handle?

Typically, the answer is "no." The mechanical properties of the different force range sensors are very similar. The polymer materials of which these sensors are composed will start to deform plastically around 8,000 PSI.
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What is a puck/shim and do I need to use it?

A puck, or shim, is an object placed between the sensing area and load (like cheese between two pieces of bread) to ensure that the sensor captures 100% of the applied load if the contacting surface is larger than the sensor diameter and to reduce high pressure for point load applications. The applied pressure should be between 1 and 10,000 PSI. If the applied force is small, e.g. 30 grams, a puck should be used to reduce the area to achieve at least 1 PSI. For applied loads that are high but have a very small area, a puck should be used to reduce PSI to below 10,000. For best results, the loaded area or puck should be between 70% (a diameter of 0.263", or area of 0.077in2 ) and 100% of the sensing area but can be reduced to achieve results as described above. Plastic pucks are recommended, as they are pliable but not too soft.
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What material is best to use?

Plastic is recommended, but you can use metal and rubber as well. The material used should not induce a large shear force on the sensor when a normal load is applied.
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How rough can the load surface be?

Use your best judgment, keeping in mind that a sharp point on the surface would likely puncture the sensor.
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What surface is best to use underneath the sensor?

A flat, smooth surface is ideal.
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Why do I need to calibrate the sensor?

With the ELFTM system, calibrating the sensor will allow you to choose force units and adjust the sensitivity based on a known load to achieve the best resolution. If you increase the sensitivity of the sensor, the maximum force range essentially shortens, giving you greater resolution.
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What is the resolution of the ELF system?

ELF electronics includes an 8-Bit (256 levels) A/D converter. In order to estimate sensor resolution, divide the maximum force range of the sensor by 256. (E.g. 25 lbs, which equals about 55kg, divided by 256 = 0.47lbs = .215kg = 215g).
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What is the maximum speed of the ELF System?

The maximum speed is 200 Hz with the standard ELF System, and 5760 Hz with the Hi-Speed ELF. The capture speed in each system is adjustable.
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Can I use more than one sensor at a time?

Yes, with the Multi-Handle ELF (MELF) software and appropriate number of handles, you can use up to 16 sensors at a time.
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Are the FlexiForce sensors waterproof?

No, the sensors are not designed for use under water, as the adhesive holding the top and bottom layer of the sensor together would likely separate.
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Does humidity have any effect on the sensor?

The sensors have been tested in high humidity, and their responses have been within normal limits.
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Can the sensors pick up electrical noise?

Yes, to a small degree.
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What are the influences of magnetic fields or radiation?

Consumers who have used the sensors around magnetic fields have reported little or no effect. The sensors' response to radiation is unknown.
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What is the smallest active sensing area you can make?

The smallest and largest are determined on a case-by-case basis, depending on the maximum force being applied. It may be possible to achieve 2mm2 as long as the PSI remains between 1 and 10,000 PSI.
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What is the maximum force range that you can make?

The custom FlexiForce sensors can be made to measure force ranges up to a few thousand pounds as long as pressure remains below 10,000 PSI.
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What is the usual turn-around time for custom designs?

From receipt of purchase order to completion of prototype, 6 - 12 weeks, depending on queue status at the time of order.
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What are the minimum and maximum quantities you can do annually?

Due to the cost involved, we typically do not design custom sensors for quantities less than 1,000. The maximum quantities that can be produced depend on several factors. 1,000,000 custom sensors per year should not pose a problem.
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Can you make custom sensors that work with the ELF System?

Yes, we can customize sensors for use with the ELF System.
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What is the average cost of a custom design?

Each request is different, depending on size, complexity of design, force ranges, quantities, etc. Please contact us to discuss your requirements and specifications.
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How can you find us?

Looking to learn more about FlexiForce?

Call us at        (718) 966-3694
or Fax us at    (718) 966-3695

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