What sizes are sensors available in?

Question: What sizes are sensors available in?

Answer: We have sensors in many shapes and sizes. Please refer to one of our five sensor catalogs to see diagrams of our standard sensors. Contact Tekscan for the sensor that would best fit your application. Custom sensors are also available.

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What is the temperature range for sensor use?

Question: What is the temperature range for sensor use?

Answer: Standard Tekscan sensors are specified to operate in a temperature range from -40 ºF to 140 ºF (-40 ºC to 60 ºC). If the sensor is used at a temperature different than the calibration temperature, there will be a temperature effect.

The operating temperature range of the Handle is 32 °F to 122 °F (0 °C to 50 °C). Thus, if the application involves extremes of temperature, the Handle should be insulated or otherwise protected from the extremes of high temperature.

Many sensors can be produced with high temperature ink and substrate for use over a temperature range from -40 ºF to 400 ºF (-40 ºC to 204 ºC). The appropriate sensor for prospective high temperature applications is individually evaluated, and quoted.

We do also have High Temperature model sensors; they are specified to operate in a temperature range from -40 ºF to 400 ºF (-40 ºC to 204 ºC). Calibration would be affected when the temperature goes beyond this specified range. Keep in mind that we do not recommend the use of the ELF system handle with our High Temperature model sensors, and if you do intend to use it with the sensors, a waiver would need to be signed.

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How fast does the developed color of Prescale fade and what is the best way to keep the measured Prescale from being deteriorated?

Question: How fast does the developed color of Prescale fade and what is the best way to keep the measured Prescale from being deteriorated?

Answer: Ultraviolet rays accelerate the fading process of the color. Therefore, please protect the Prescale from ultraviolet rays by keeping it in a file and storing the file in a cabinet. The color will gradually fade even when storing the film in this manner. It is recommended that you measure the pressure values with a pressure measurement system within 60 minutes of applying the pressure and that you keep the data in digital form for reference.

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How does the level of accuracy change as curvature of surfaces increases?

Question: How does the level of accuracy change as curvature of surfaces increases? In other words, what level of curvature causes so much crimping in the sensor that readings lose accuracy? Is contact area affected by the curvature or does this just affect the pressure readings?

Answer: Curvature or wrinkling of the sensor will produce a preload on the sensor. This will affect both the pressure readings and the measured contact area. The extent of this preload is dependent on the radius of curvature and on the pressure range of the sensor. Sensors with lower pressure ranges are more sensitive and will be more inclined to produce readings induced by curvature of the sensor.

Curved Contact Surfaces When studying contact between soft or curved objects such as the foam of a bed or chair and human flesh, or artificial knee joints, calibrate with the objects being studied, not with an equilibrator. That way the curvature that evolves between the surfaces in calibration is similar to the curvature of the experiments. To better understand this, consider a free body diagram of a concave curved surface supporting a convex vertical load. The total resulting vertical force vector results from many individual local vectors with opposing horizontal components, which cancel out. Tekscan sensors respond to the individual local normal forces, and the software sums these forces (assuming the sensor is flat).

Curved contact surface

Tekscan sensors are made with s dimensionally stable substrate: polyester sheet. A dimensionally stable sheet rolls nicely around a simple curve such as a cylinder or cone. Thus, measurements can easily be taken on a coffee cup, rolling pin, or the body of a ballpoint pen. A dimensionally stable material has difficulty wrapping smoothly over a ball, or someone´s nose or chin. If the sensor crinkles, or develops folds, it is prone to report high-pressure output where little or no pressure is applied. These locations may be “tared out”, the bottom threshold of the legend can be raised, or they can be edited out of the movies altogether.

When loading soft interfaces, such as a crash dummy or a person onto a foam/cushion, try to calibrate with the actual materials and with the actual profiles/curvature. Curved contact surfaces with complex curves may be measured with Tekscan´s sensor models 6900, 9801, or 9830 since they have narrow sensing areas (“fingers’) that lend themselves to positioning on contoured surfaces with minimal artifact generated from the geometry.

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Different values for the feedback resistor in the recommended FlexiForce circuit

Question: What is the effect of changing the value of the feedback resistor used in the circuit in the manual?

Answer: If you are using our recommended circuit, a feedback resistor at half the recommended 20 kΩ value will increase the range to about double its stated range (up to ~0-50 lbs from ~0-25 lbs). If you only interested in measuring forces up to 4.5kg (~10 lbs), you should double the feedback resistor (rather than halving it). A feedback resistor of about 40kΩ would decrease the dynamic range to about 0-12 lbs.

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Changed settings are not remembered after the software is closed

Issue: When I change settings, they are not remembered the next time I start the software. These settings may include:

  • User Preferences
  • Recording frequency
  • Frame rate
  • Recording duration
  • Recording trigger parameters
  • Units of measure and the number of decimal places they are reported with
  • Display properties

Solution: These parameters are stored in an *.ini (configuration settings) file that is stored in the same folder as the Tekscan software. This file will be named with the same file prefix as the Tekscan program you own. For example, if you have Tekscan's I-Scan™ software, the corresponding file will be named iscan.ini.

The likely cause of the problem is that, either this *.ini file is set to be read-only, or, the Windows user account, which is currently logged onto the computer, does not have permission to make changes to the folder where the Tekscan software is installed. This *.ini file records changes to any settings that are changed. If you cannot change this file, then the software will always revert to the original settings in this file.

Log on to the computer with the Windows Administrator account. Then, try changing the acquisition parameters or the measurement unit settings and close the software. If this changes the setting permanently, then you will know that this is a user rights issue. Also, check the properties of the Tekscan folder to make sure that the files in this folder are not set to read-only.

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Periodic saturated (red) frames during recordings with Tekscan PCI electronics and computers with Hyperthreading enabled

Issue: Periodic saturated (red) frames during recordings with Tekscan PCI electronics and computers with Hyperthreading enabled

Saturated values in frameSaturated values in frameSolution: This occurs when collecting recordings with Tekscan PCI electronics connected to a computer with a Pentium 4 processor 3.0 GHz or higher and hyperthreading technology enabled. While collecting the recording, occasional frames will have large areas that display saturated values. These values are displayed as red blocks within the recording window as shown in the image.

When hyperthreading technology is enabled in the computer's processor, this creates a timing problem while collecting data from the Tekscan PCI board. Hyperthreading is technology introduced by Intel with their Pentium 4 processors. It allows a single computer processor to act as two parallel processors and execute two threads of software code simultaneously. The Tekscan recording process requires the full resources of the processor, especially when recording at speeds over 50 Hz.

The presence of two processors can be seen in the windows device manager. To see this, right click on "My Computer" and select Properties. Under the Hardware tab will be a button to open the Device Manager. Click the + sign next to Processors and there will be two processors listed if the computer is using hyperthreading or has two physical processors.

Device Manager - Processors

When hyperthreading is enabled on a computer, this creates an occasional timing problem with the Tekscan PCI board during recording. This causes the Tekscan software to momentarily lose communication with the PCI board and when this occurs, the software displays saturated data for these frames.

This problem can be resolved by disabling Hyperthreading in the BIOS of the computer. This should not prevent other software programs from running, but it is possible that some programs specifically designed to take advantage of hyperthreading may perform more slowly. The manufacturers of these programs should have more information on how disabling hyperthreading may affect their software.

To enter the BIOS, reboot the computer and follow the commands for entering Setup that appear immediately after the computer starts and before Windows begins loading. Typically there are instructions to push the F2 key to enter the Setup console, but this key may be different on some computers.

Once in the BIOS, there should be a menu for CPU information, and within this menu, a toggle switch to turn hyperthreading On or Off. This should be set to Off. Then Exit the BIOS and Save the changes.

Because making changes to the BIOS can have other effects on your computer, any users unsure of making these changes themselves should contact their computer's manufacturer for more details on BIOS changes and disabling hyperthreading.

This problem will also exist on computers that have two physical processors. If this is the case, the computer's manufacturer may be able to offer instructions for disabling one of the processors. Otherwise, a computer with only a single processor will be required for the Tekscan software.

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How to convert .fsx movie files recorded in the Tekscan software into a standard movie format?

Question: How can I convert .fsx movie files recorded in the Tekscan software into a standard movie format? If this is not possible with your software, what do you recommend?

Answer: This cannot be done directly from the Tekscan software but, you can capture the movie to an *.avi file using a couple of different dynamic screen capture products.

These screen capture programs can record what is happening on your computer screen and can save this information as an AVI (*.avi) file -- a popular digital video format. Think of yourself holding a video camera to capture what is occurring on-screen. You can record the *.fsx movie in your software, and save the screen movement as an *.avi file. To do this, you could start the Tekscan software and play back a Tekscan movie, while capturing the screen image to video with the dynamic screen capture software.

A full explanation of how to use screen video capture software is beyond the scope of this document; however, here are two products that can capture screen information to an *.avi file:



Information on their use of these products can be found at the above websites.

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How to convert Resistance (Ohms) to Force (lbs)?

Question: How can I convert Resistance (Ohms) to Force (lbs)?

Answer: The easiest way to convert Ohms to lbs is via a simple calibration curve (Excel works great). Take our sensor and place known weights on it, record the resistance (with a multi-meter or other suitable resistance reader), repeat until you have as many points as possible. This is a very elementary curve, which will not be linear. The Conductance (inverse of resistance (1/R)), however, will be relatively linear. Graph Conductance vs. Force and fit it with a line of best fit. The corresponding Y=mx+b equation that fits the line will be your resistance to force correlation. Y is the conductance value (1/R) you read when testing, m and b are constants found via the line of best fit calibration, and x is the corresponding output force value in lbs assuming you calibrated with known lb weights.

Conductance vs force graphConductance vs force graph

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How do I purchase additional sensors for my Tekscan system?

Question: How do I purchase additional sensors for my Tekscan system?

Answer: You can purchase additional sensors directly from Tekscan.

Simply call us at (800) 248-3669 (International 001-617-464-4500) or fill out the contact us form.

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