videoXtens
The basic version of videoXtens consists of a housing with a camera. It can be expanded with an additional camera in the housing or alternatively with a complete measuring head including a camera.
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videoXtens is used for optical measurement of extension on contact-sensitive and highly elastic materials.
This extensometer provides non-contact measurement of tensile, compressive and flexural deformations of all types of plastics, metals, rubber, composites and films/foils and of two-dimensional point displacements within a matrix, e.g. on components.
It is also suitable for determining change in width, r-values as per ISO 10113 and ISO 10275 and offset yields in tensile tests to ISO 6892-1.
What versions is the videoXtens extensometer available in? How does this measuring system actually work? What is the correct way to prepare the specimen for accurate, reproducible measurement? How does the test work under extreme temperatures? All these answers and much more can be found here.
videoXtens versions
Advantages and features
Specimen marking
In the case of materials with smooth, monochrome surfaces the gage length is marked using a felt-tip pen or by means of self-adhesive gage-marks. Alternatively the specimen can be prepared by applying a pattern spray to the surface area. Extension is measured using the pattern created by the texture applied at points on the gage-length. Specimens with a structured surface can be tested even without additional marking; the surface texture serves as a natural pattern.
No extra marking is required for optional change-in-width measurement. Measurement is via a special edge-detection algorithm (Second Measurement Axis option).
The transverse-contraction gage-length can also be set by applying dots or by selecting areas of a natural or artificial pattern on the specimen surface.
Due to gage-length compensation the same degree of accuracy is not required when applying gage marks at distance L0 as with other fine-strain measurement methods. This eliminates error sources while speeding up test preparation.
Temperature chamber
When videoXtens is used in conjunction with temperature chambers, ensure that the panes in the observation port are made of anti-reflective glass; otherwise the signal quality may be significantly impaired by reflections and light loss.
The changed optical testing conditions will also have a negative impact on the measurement signal. In the temperature range from 0 to +250°C this basically refers to air currents which occur in the temperature chamber and cause an increase in signal noise of approximately 0.1 µm per 10 kelvin temperature increase.
In the minus temperature range down to -70°C, mist formation and icing of the specimen and fixture may occur; the effect on the measurement signal depends on the customer-specific configuration (coolant medium, specimen grips, illumination, specimen material etc.). In chambers employing CO2 and LN2 cooling there is a danger of mist formation, given suitable humidity levels and temperatures of approximately -20 to 0°C. It may then be necessary to wait several minutes before performing the test.
When standard self-adhesive marks are used the temperature range is limited to -40 to +120°C. Marker pens offer alternative options.
For applications requiring frontal illumination of the specimen the standard incident light lamps are available. These are mounted outside the chamber and light the specimen through the videoXtens observation port.
7:42
Ribbed steel test with 2-camera videoXtens extensometer
The test re-run software options and strain distribution facilitate measurement across the entire length of the specimen and a subsequent recalculation of the strain
videoXtens
Measuring head with digital camera, software for image acquisition and evaluation, plus accessory case for alignment and marking aids.
Item no. |
1001282 |
|
---|---|---|
Type |
videoXtens |
|
Only for AllroundLine and zwickiLine (zwickiLine not together with safety shield) |
||
Initial gauge length L0 |
5 to approx. 500[1] |
mm |
Resolution per field of view: |
||
50 mm |
0.25 |
µm |
100 mm |
0.5 |
µm |
200 mm |
1 |
µm |
500 mm |
2.5 |
µm |
Measuring frequency, max. (can be set) |
166 |
Hz |
Max. test speed |
1000 |
mm/min |
Max. specimen thickness |
20[2] |
mm |
Weight, approx. |
7.5 |
kg |
Accuracy |
Accuracy class 1 to EN ISO 9513 for field of view ≤ 200 mm For fields of view > 200 mm, the following applies: The smallest measured value in Accuracy Class 1 is: FOV/1000. Example:FOV=500mm⇒500mm1000=0.5mmAccuracy Class 1 is attained at a measured value of 0.5 mm or above. |
A free slot in testControl II is required for the INC module (included in delivery).
videoXtens Array
Expanded measuring head with three digital cameras, software for image acquisition and evaluation, plus accessory case for alignment and marking aids.
Item No. |
1001392 |
|
---|---|---|
Type |
videoXtens Array (3 cameras) |
|
Initial gage-length L0 |
5 to 300 |
mm |
Resolution per field of view: |
||
140 mm (f = 50 mm lens) |
0.25 |
µm |
230 mm (f = 55 mm lens) |
0.4 |
µm |
340 mm (f = 25 mm lens) |
0.6 |
µm |
Accuracy |
Class 1 |
to EN ISO 9513 |
Measuring frequency, max. (adjustable) |
166 |
Hz |
Max. test speed |
1000 |
mm/min |
Weight, approx. |
15 |
kg |
testXpert II minimum version |
V 3.4 |
A free slot in testControl II is required for the INC module (included in delivery).
videoXtens for ProLine
Measuring head with digital camera, software for image acquisition and evaluation, plus accessory case for alignment and marking aids.
Item no. |
013561 |
|
---|---|---|
Type |
ProLine videoXtens |
|
For ProLine only |
||
Initial gauge length L0 |
5 to 500 |
mm |
Resolution in the field of view: |
||
50 mm |
0.5 |
µm |
100 mm |
0.5 |
µm |
200 mm |
1 |
µm |
500 mm |
2.5 |
µm |
Accuracy (for field of view ≤ 200 mm) |
Class 1 |
to EN ISO 9513 |
Measuring frequency, max. (adjustable) |
65 |
Hz |
Max. test speed |
1000 |
mm/min |
Weight, approx. |
7.5 |
kg |
Connected directly to PC, no module required.
testXpert III testing software offers various options for precise, traceable non-contact extension and strain distribution measurement.
Test Re-Run and strain distribution
The optional Test ReRun module enables retrospective recalculation of strain on the basis of an image series recorded during a test, using a different initial gage-length (provided multiple markings are present). This can be particularly advantageous in component testing, for example, when it is necessary to evaluate local strain at different locations, or in standard tensile tests when specimen necking has occurred outside the original initial gage-length.
The recalculated strain can naturally be synchronized retrospectively with the other
measured values via testXpert testing software.
(This option is available with testXpert II Version 3.4 onwards.)
Dehnungsverteilung
Video Capturing
The testXpert III Video Capturing software option is recommended if recording of the
test is additionally required (without retrospective recalculation). The recording is
synchronized with the measured curve, enabling the test to be viewed retrospectively. The
option includes no hardware, as recording and synchronization take place entirely via the
videoXtens system.
This option is free of charge.
2D dot matrix
This option allows two-dimensional measurement of dots applied to a planar specimen surface. This enables determination of local strains and specimen inhomogeneities under load. X and Y co-ordinates plus the distances between dots are available as measured values.
Up to 100 measurement dots can be measured in any desired arrangement or in matrix form. Display in testXpert III is limited to 15 channels.
This option uses only one camera for measurement; any other cameras present are switched off beforehand.
Optional second measurement axis
This option allows biaxial measurement; transverse strain (e.g. change in width) can be recorded at the same time as longitudinal strain. Alternatively, change in width can naturally be measured alone.
Deflection measurement
videoXtens can also be used for flexure tests. There are several options for measuring specimen deflection, depending on the type of test and the specimen condition and properties:
Maximum deflection that can be measured: with videoXtens the maximum deflection corresponds to the FOV; with videoXtens Array to 1/3 of the total FOV (deflection is measured with one camera only in this case).