How often should I calibrate the texture analyser?
Many people ask this question. The texture analyser does not need to be calibrated every time you use it. Normally, as a guideline we would suggest that you calibrate at least once a month, if the texture analyser is moved to a different position and if you cause an overload. However, as calibration only takes a matter of seconds you could calibrate every day if you prefer.
When I receive a software upgrade how can I find out what has changed between the new and last version?
When you install the software you are asked if you would like to view the notes file. This file contains a list of the changes made to each version. The file is called "notes.txt" and is installed into the application directory so you can view this at any time using notepad.
Do I have to use paraffin oil to lubricate the Kieffer dough forms?
Several users have asked about the relevance of using paraffin oil for dough testing equipment rather than ordinary vegetable oil. It is not incorrect to use vegetable oil if this is all that is available but you may find that the equipment becomes sticky after a time and may discolour e.g. the Kieffer dough forms may become yellow. Paraffin oil does not have this problem as it does not oxidise like vegetable oil.
What data acquisition rate should I choose for collecting test data?
When measuring crispness, Brittleness or fracture the events occur very quickly. In order to obtain an accurate understanding of the fracture events one should try to obtain as many data points as possible. By using a data acquisition rate as low as e.g. 50pps you may indeed be missing the true picture of what is really happening in terms of fracture. For brittle products, therefore, a data acquisition rate of 400 or 500pps is recommended. This rate allows a maximum testing time of 1 minute which is usually sufficient time for the testing of such ‘quick-breaking’ products.
When testing products that are not brittle and do not necessarily fracture (i.e. fast events need not be captured quickly) a data acquisition rate of 200pps is recommended. At 200pps data is still captured very accurately and at this speed the test will not take up as much space on your hard drive.
If a test is required to run for a much longer period, e.g. a number of hours or days, then a much lower data acquisition rate must be chosen, i.e. at 4pps a test time of 2hours and 5 mins is permitted whilst at 0.1pps one may test constantly for up to 3 ½ days.
Occasionally my texture analyser appears to start collecting data in mid-air, i.e. before it has reached the test sample. Why is this?
The following is a list of reasons associated with the ‘early triggering’ problem which customers may encounter. The texture analyser may trigger early if:
- The trigger force is set lower than 5g when a 25kg load cell is installed.
- An open window or circulating fan is located near to the texture analyser.
- Screws on the load cell plug are not tightened and therefore vibrate.
- Incorrectly fitted probes.
- Inertia (i.e. heavy probes)
- Vibration on the table on which the texture analyser is situated which may be from other equipment or e.g. drilling in a nearby room.
I appear to have lost the Teflon sleeve off the end of my Kieffer rig hook. Will this affect my results?
We have found that several users have lost the Teflon sleeve that fits over the hook of the Kieffer Dough and Gluten Extensibility Rig. This sleeve is to prevent the dough breaking at the hook point and is therefore important when performing this test. Please contact us if you need us to send replacement sleeves.
I appear to get a lot of ‘noise’ on my curve (produced using a Kramer shear cell), even when the blades are not touching the sample. Why is this?
When setting up a fixture such as a:
- Blade set
- Kramer shear cell,
- Forward extrusion cell
- Ottawa cell
it is important to avoid friction of the probe on other surfaces of the fixture which can contribute to a considerable amount of measured force which is not due to the testing of the sample itself. When the fixture is set up it is recommended that users perform a ‘blank’ test (i.e. a test should be run with no sample) so that the frictional force (if any) can be measured to see what contribution it will be making to the measurement. In the case of the forward extrusion a small frictional force of the piston against the cylinder interior cannot be avoided but can instead be substantially reduced by careful positioning.
How can I check that the force calibration is correct?
A simple check of the calibration is to place known weights on the calibration platform to check the reading on the TA keyboard by using the ‘FAST - RESET’ function (‘live weigh mode’) on the TA keyboard.
Can you give me further information to consider regarding the force calibration of the texture analyser?
Points that should be noted when performing force calibration:
The calibration weight should not be lifted off the calibration platform too soon - wait for instructions from the software (if applicable) - do not follow instructions from the keyboard when ‘done’ is displayed if you are using the software.
The correct calibration weight should be used which depends upon the load cell capacity.
Overload/Underload should not cause force calibration problems but in any event calibration is very quick to perform and is therefore recommended. However overload/underload does lose the probe height calibration and ‘CAL’ is then displayed on the keyboard.
When should I use a ‘Button’ trigger type instead of an ‘Automatic’ trigger type?
First of all, a brief explanation of both trigger types:
Button: Measurement starts as soon as the Run command is given and the probe starts moving.
Auto: The Texture Analyser will move the probe up (Tension test) or down (Compression test) until it detects a force greater than the Trigger Force setting. Measurement starts once this force point is reached. This ensures that products of different sizes are accounted for. This facility also allows the Texture Analyser to measure the product height (particularly important when measuring in strain). Sometimes you can experience false triggering when using the Auto option. If this is the case then try increasing the Trigger Force setting.
Most products should be tested with an automatic trigger for detecting the surface of the sample and starting to collect the test data. The penetration, cutting or compression distances etc. are then identical for all automatic trigger tests without regard to the precise height and geometry of each sample tested.
The sensitivity of the automatic trigger can also be used to adjust for minor differences in sample geometry and sample preparation. For example, if you used a 3g trigger force for a product with an irregular surface you would almost certainly get relatively extreme differences in the depth of penetration, based on how deep the surface irregularities were. If the surface irregularities were from peaks like those on whipped cream, you could negate the surface irregularity impact by using e.g. a 25g trigger force, so the light surface peaks would be ignored, and the penetration distance would start at a more consistent product surface, i.e. when the probe and product surface have full contact.
The sensitivity of the automatic trigger can also adjust for differences in probes. For example, if you used a 3g trigger with a 3mm cylinder probe the TA.XT2 may not detect the surface of a very soft gel until the probe is 4-5mm into the gel. Perhaps much better consistency between hard, soft and very soft gels could be attained by using a much lighter trigger force, or even a button test where the probe can be more precisely positioned over the sample by eye (or preset positions). Of course, using a different probe would also be suggested for gels.
Button tests are particularly good for testing the Firmness of e.g. pastes, doughs and other products where geometry is difficult to control. We also highly recommend a Button trigger type when using the Kramer Shear cell and Ottawa cell. These attachments are often used when testing products of differing heights such as compressing a portion of cereal flakes. In these instances you can program the probe to travel a fixed distance so that the product, whatever its original shape or height, is deformed to a consistent height or cut to a constant gap. For example, if you calibrate a probe to 10.0mm over the base, and then use a button trigger with a Return to Start tests to travel 9.0mm, you will always deform or cut the product to a 1mm distance from the base.
What minimum trigger forces do you recommend?
When using an automatic trigger type our guide as to minimum trigger forces is:
5kg load cell – 0.5g
25kg load cell – 5g
50kg load cell – 7g
The trigger force is extremely sensitive and could result in a false surface detection in ‘vibration noisy’ environments such as production floors or high-traffic R&D labs. In such locations we recommend a trigger force of at least 5g for 5kg load cells, and perhaps as high as 20g for 25kg and 50kg load cells.
Choosing an optimum trigger force is a balance between one high enough to avoid triggering in the air during the downstroke and low enough to be sensitive to the true surface of your product. A short period of experimentation will help you find the right trigger for your product. It is difficult to recommend a perfect trigger force for each test as there are several variables to consider, namely, trigger force will depend on the size of the probe and/or product for testing, the Hardness of the product and the irregularity of the product surface. Other trigger force considerations are explained in a previous question and answer above.
Can you explain the ‘Stop Plot at’ feature in the T.A. Settings window?
This option instructs the Texture Expert (and Texture Expert Exceed) software to stop collecting data at certain points during the test.
Trigger Return: Stops plotting data when the arm returns to the point at which it triggered. For tests which used an Auto style trigger, this will plot the return until the trigger force is reached. For Button style tests the Trigger Return Setting would be the same as Final.
Reset: Keeps plotting data until the buffers are full or the Reset key (on the TA keyboard) is pressed.
Final: Stops plotting data when the probe returns to the original starting position. We recommend that you use this Final setting as your default so that all data is collected. As you gain confidence in using the TA.XT2 you can always change to one of the other settings at a later data.
Target: Stops plotting data when the target force or distance is reached and the final value has been recorded on the keyboard. In the popular Return-To-Start style test this will plot the downstroke only, and will not plot any of the return behaviour. We do not recommend this option for most users. This setting is useful for those who are only interested in sample behaviour up to e.g. a fracture event, and are also interested in reducing the size of their archive files.
NOTE: Some of these features are only available in versions in the firmware 6.04 and above.