Frequently Asked Questions
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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Can LabVIEW be used with ELF? *
Yes, we now have the ELF LabVIEW VI
Driver software, which allows the ELF System 1 to be used
within LabVIEW in real-time. LabVIEW is a software product that
allows users to collect data from a variety of inputs and process
the data graphically. To Request More Information on LabVIEW, refer
to What is LabVIEW?
*LabVIEW driver is not compatible with Hi-Speed
ELF.
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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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