This was the best explannation video that I've seen. Very well explained starting with the theory and gave a good experimental explanation along with practical explanation. Worth the watch time!!!
@@DynatecIndia Thank you so much! By the way, do all 4 strain gauges require an equal increase in resistance DeltaR for the bridge to work? The structure I am working with behaves differently at the top than at the bottom (composite) so my strains differ.
@@tepochcalli I would like to reply as follows: Assuming that all the gages in the bridge are having the same initial resistance R, the output from the wheatstone bridge is given by : e(output) = Excitation voltage ( dr1 - dr2 + dr3 - dr4) / (4R) Where dr1, dr2, dr3 and dr4 are the changes in the gage resistances in ADJACENT arms of the wheatstone bridge, and these values are positive for tension and negative for compression. So the DeltaR for all the gages do not have to be of the same magnitude, but must be having opposite sign in adjacent arms, to get an output from the bridge. Example 1: If two gages in adjacent arms change by dr1 and (-dr2) for positive and negative strain respectively, then the output of the bridge will be E (dr1 -(-dr2) +0-0) /(4R) = E ( dr1+dr2)/(4R) Example 2: If all 4 gages in adjacent arms change by dr1 (-dr2), dr3 and (-dr4) for positive and negative strain respectively, then the output of the bridge will be E (dr1 -(-dr2) +dr3-(-dr4)) /(4R) = E ( dr1+dr2+dr3+dr4)/(4R) It is not necessary for dr1,dr2,dr3, dr4 to have the same magnitude, such as in your case where the gages are at different locations. However it would be very much preferable to carry out a calibration with known load or force, and plot the bridge output vs load. For instance, in a column load cell designed for compression, two gages are aligned along the long axis and will be in compression, while two more gages are aligned in the transverse direction and will be in tension(sujected to poisson strain). The gages are connected in compression-tension-compression-tension inseries, but the tension gages will see only the poisson strain , around 1/3 the strain of the gages subjected to compression. The load cell will however be calibrated by actual loading, to determine the output vs load relation. I hope this is clear, please let me know if I can clarify further.
Thank you am algeria repair scal weighing à have load cell for scal valum is 350 hom can you dising how connected and install strain gage on a réalisé loadceel.
The instrument is called Model P3 Strain Indicator and Recorder.Manufactured by Vishay Micro Measurements in USA. Website: www.micro-measurements.com. Please write to us for more details at vijay.dynatec@gmail.com
The straingage responds to strain on the part to which it is bonded. It has to be made part of a wheatstone bridge as described earlier, and connected to a strain indicator such as the model P3 from Micro Measurements. The output from the straingage will be indicated on the instrument directly in terms of microstrain on the part when subjected to loading. Regards
@@amiridham3117 The strain gage is very sensitive, and unfortunately it does require a very stable and sensitive instrument designed for this specific sensor, to give a reliable measurement. Please plan to procure one. Best regards
If all the 4 straingages in a wheatstone bridge are bonded on the same part close to each other, all the gages will react equally to any temperature changes , and in a full bridge configuration we can expect these changes to cancel each other, so the effect on the out put of the bridge is insignificant. This is considered adequate for most stress analysis applications In transducer applications where even small errors are not tolerated, further temperature compensation is carried out by adding small resistance wires made of Balco, which is sensitive to temperature changes, to an individual arm of the bridge to compensate for the temperature change. Adding this resistance in the arm of a bridge will un-balance the bridge, and this unbalance is compensated by adding a similar manganin wire( which is insensitive to temperature changes) in the adjacent arm to remove the offset caused by the Balco wire. Each time a change is made, the part is subjected to temperature changes and tested for adequate compensation, Regards
@@DynatecIndia Very clear and instructive video, my sincere compliments! I have a question about temperature correction: we want to measure the elongation of a rod that is subjected to tension. Applying one strain gauge makes the measurement very sensitive to temperature differences. How should we apply 4 strain gauges on the rod for keeping them on the same temperature? I would say R1 and R3 in axial direction and R2 and R4 in tangential direction but I'm not sure...
@@hugogroeneveld5404 That is correct - R1 and R3 in axial direction, and R2 and R4 in the transverse direction. All the gages will be at the same temperature. However the output of the wheatstone bridge will be 2.6 times , not 4 times the output as from a single gage. This is due to the poisson effect. (Sorry I did not see your comment earlier..)
Why are strain gauge resistor assemblies made so small? I think if they are made long - like almost as long as the metal bar they are stuck on - then the change in resistance would be higher. Do longer strain gauges exist? If not, is there any specific reason for strain gauges be this size?
Strain gages are made to internationally accepted resistance values. The most popular values are - 120 ohms and 350 ohms. This is regardless of the size of the gage. The change in the resistance of the gage is dependent on the strain in the part on which they are bonded. Strain is a ratio, and as a ratio, in a uniform strain field, it is the same regardless of the length of the strain gage. Example a strain gage with a length of 3mm will change in resistance by the same amount , and measure the same value of strain, as a strain gage having a lendth of 6 mm. Strain gages will average the strain over the grid area. In a uniform strain field, the average will be the same if the gird size is more or less, but if the part has a high strain gradient, gages with different sizes will give different readings. To measure the peak strain at a point, it is important to choose a small gage to cover just the peak strain area as far as possible. For non-homogeneous materials such as concrete, rock or fibre-reinforced plastics, it is necessary to average the strain over a large area to miimise the effect of highly localized high and low strains, and for this strain gages of 25 mm, 50 mm and 100 mm grid length are available. as well as very small gages of 0.2 mm grid length for demanding applications. Please see our video STRAIN GAGE AVERAGING EFFECT on UA-cam, under the channel Dynatec India.
Bom dia ! poderia demostrar montando em uma célula de carga ! Obrigado ! Sucesso!(Brasil) (Português) Thank you for your comment, I am glad my presentation was helpful, Regards, Vijay
Greetings from California,
This was fantastic information and very well-worded. Thank you sir!
Thank you very much for your kind comments. I am working on some more topics related to strain gages, and will post them on UA-cam soon.
Thank you very much for your comments. Regards.
This was the best explannation video that I've seen. Very well explained starting with the theory and gave a good experimental explanation along with practical explanation. Worth the watch time!!!
Thank you for the comment, glad to know it was helpful to you. Best regards
you are the first I have come across to actually explain that to where I can fully understand it. thank you.
Thank you for your kind comments, I am glad that my video was useful to you.
God bless engineering Indian guy on youtube answering all our engineering related questions.
Thank you for your kind comment. I will be glad to assist further on straingage related queries.
@@DynatecIndia Thank you so much! By the way, do all 4 strain gauges require an equal increase in resistance DeltaR for the bridge to work? The structure I am working with behaves differently at the top than at the bottom (composite) so my strains differ.
@@tepochcalli I would like to reply as follows:
Assuming that all the gages in the bridge are having the same initial resistance R, the output from the wheatstone bridge is given by :
e(output) = Excitation voltage ( dr1 - dr2 + dr3 - dr4) / (4R)
Where dr1, dr2, dr3 and dr4 are the changes in the gage resistances in ADJACENT arms of the wheatstone bridge, and these values are positive for tension and negative for compression.
So the DeltaR for all the gages do not have to be of the same magnitude, but must be having opposite sign in adjacent arms, to get an output from the bridge.
Example 1: If two gages in adjacent arms change by dr1 and (-dr2) for positive and negative strain respectively, then the output of the bridge will be E (dr1 -(-dr2) +0-0) /(4R)
= E ( dr1+dr2)/(4R)
Example 2: If all 4 gages in adjacent arms change by dr1 (-dr2), dr3 and (-dr4) for positive and negative strain respectively, then the output of the bridge will be E (dr1 -(-dr2) +dr3-(-dr4)) /(4R)
= E ( dr1+dr2+dr3+dr4)/(4R)
It is not necessary for dr1,dr2,dr3, dr4 to have the same magnitude, such as in your case where the gages are at different locations. However it would be very much preferable to carry out a calibration with known load or force, and plot the bridge output vs load. For instance, in a column load cell designed for compression, two gages are aligned along the long axis and will be in compression, while two more gages are aligned in the transverse direction and will be in tension(sujected to poisson strain). The gages are connected in compression-tension-compression-tension inseries, but the tension gages will see only the poisson strain , around 1/3 the strain of the gages subjected to compression. The load cell will however be calibrated by actual loading, to determine the output vs load relation.
I hope this is clear, please let me know if I can clarify further.
Greetings from Montreal !
A very well explained video ! Keep it up !
As always, Vijay does an excellent job of explanation and illustration. Well done.
Thank you for all the encouragement and support
Your explanation made it so easy to understand it's working. 👍👍👍🙏
Thank you. Please write to me at vijay.dynatec@gmail.com for any further assistance.
Regards
Hello from Rio de Janeiro! Great work, Vijay!
Thank you for your kind comments. Regards, Vijay (vijay.dynatec@gmail.com)
Very helpful video to get the practical information about strain gauges
Thank you very much for your kind comments. I will be glad to answer any queries you may have. Best regards
Hi quick question. For a full bridge strain gauge setup, does it matter which specific strain gauges are on the top or bottom surface?
Thank you am algeria repair scal weighing à have load cell for scal valum is 350 hom can you dising how connected and install strain gage on a réalisé loadceel.
Can I calculate strain by connecting the output voltage of Wheatstone bridge to Arduino and display it on a lcd display?
What is the advantage of using 4 gauges instead of 1 if you can just multiply your value from one gauge? Is it more useful in non-linear situations?
Thank you so much!
I am glad you found the presentation useful. Regards
Name of that machine to which the wires of strain guage are connected?
The instrument is called Model P3 Strain Indicator and Recorder.Manufactured by Vishay Micro Measurements in USA. Website: www.micro-measurements.com.
Please write to us for more details at vijay.dynatec@gmail.com
Good one, thanks man! respect
The strain gauge give what value and unit?
The straingage responds to strain on the part to which it is bonded. It has to be made part of a wheatstone bridge as described earlier, and connected to a strain indicator such as the model P3 from Micro Measurements. The output from the straingage will be indicated on the instrument directly in terms of microstrain on the part when subjected to loading.
Regards
Thank you so much for explaination. I dont have facilities like p3 model to get the data 😣
@@amiridham3117 The strain gage is very sensitive, and unfortunately it does require a very stable and sensitive instrument designed for this specific sensor, to give a reliable measurement. Please plan to procure one.
Best regards
Alright thank you for your explanation i really appreciate it
@@amiridham3117 I will be glad to assist further if you send me your queries to me e-mail ID vijay.dynatec@gmail.com
what about temperature compensation?
If all the 4 straingages in a wheatstone bridge are bonded on the same part close to each other, all the gages will react equally to any temperature changes , and in a full bridge configuration we can expect these changes to cancel each other, so the effect on the out put of the bridge is insignificant. This is considered adequate for most stress analysis applications
In transducer applications where even small errors are not tolerated, further temperature compensation is carried out by adding small resistance wires made of Balco, which is sensitive to temperature changes, to an individual arm of the bridge to compensate for the temperature change. Adding this resistance in the arm of a bridge will un-balance the bridge, and this unbalance is compensated by adding a similar manganin wire( which is insensitive to temperature changes) in the adjacent arm to remove the offset caused by the Balco wire.
Each time a change is made, the part is subjected to temperature changes and tested for adequate compensation,
Regards
@@DynatecIndia Very clear and instructive video, my sincere compliments! I have a question about temperature correction: we want to measure the elongation of a rod that is subjected to tension. Applying one strain gauge makes the measurement very sensitive to temperature differences. How should we apply 4 strain gauges on the rod for keeping them on the same temperature? I would say R1 and R3 in axial direction and R2 and R4 in tangential direction but I'm not sure...
@@hugogroeneveld5404 That is correct - R1 and R3 in axial direction, and R2 and R4 in the transverse direction. All the gages will be at the same temperature. However the output of the wheatstone bridge will be 2.6 times , not 4 times the output as from a single gage. This is due to the poisson effect. (Sorry I did not see your comment earlier..)
Why are strain gauge resistor assemblies made so small? I think if they are made long - like almost as long as the metal bar they are stuck on - then the change in resistance would be higher. Do longer strain gauges exist? If not, is there any specific reason for strain gauges be this size?
Strain gages are made to internationally accepted resistance values. The most popular values are - 120 ohms and 350 ohms. This is regardless of the size of the gage.
The change in the resistance of the gage is dependent on the strain in the part on which they are bonded. Strain is a ratio, and as a ratio, in a uniform strain field, it is the same regardless of the length of the strain gage. Example a strain gage with a length of 3mm will change in resistance by the same amount , and measure the same value of strain, as a strain gage having a lendth of 6 mm.
Strain gages will average the strain over the grid area. In a uniform strain field, the average will be the same if the gird size is more or less, but if the part has a high strain gradient, gages with different sizes will give different readings. To measure the peak strain at a point, it is important to choose a small gage to cover just the peak strain area as far as possible.
For non-homogeneous materials such as concrete, rock or fibre-reinforced plastics, it is necessary to average the strain over a large area to miimise the effect of highly localized high and low strains, and for this strain gages of 25 mm, 50 mm and 100 mm grid length are available. as well as very small gages of 0.2 mm grid length for demanding applications.
Please see our video STRAIN GAGE AVERAGING EFFECT on UA-cam, under the channel Dynatec India.
Thanks for the detailed response!
how we can get strain guage kindly reply
You can contact us at vijay.dynatec@gmail.com for your requirements
Bom dia ! poderia demostrar montando em uma célula de carga ! Obrigado ! Sucesso!(Brasil) (Português)
Bom dia ! poderia demostrar montando em uma célula de carga ! Obrigado ! Sucesso!(Brasil) (Português)
Thank you for your comment, I am glad my presentation was helpful,
Regards, Vijay