Strain measurement system

[hokhay]

Hi all,

I am an CAE engineer and my company wants to purchase a strain measurement system for validation of the simulation result. We are planning to compare static load and natural frequency of a part with FEA result.
Since I have no experience in strain measurement system, I am a bit confuse of what to look for in the system.

I have already contacted Kyowa and they suggest me two strain measurement systems, PCD-400A and EDX-10/14A. The difference between these two system are as following:

PCD-400A:
Constant sampling freq. 10kHZ for different number of channels connected
AC bridge excitation (better noise isolation)
Dynamic response freq. 200Hz

EDX-10/14A:
Sampling freq. drop from 20kHz to 5kHz when number of connected channels increase
A lot more compact in size
DC bridge excitation
Dynamic response freq. 2kHz

Basically, I do not know how much different does it make between AC and DC excitation in terms of result quality. Will the result be too noisy to get any useful information to compare with FEA result? Does dynamic frequency response affect the natural frequency measurement or only sampling frequency matter?

Does anyone has any other specification to look at when purchasing this system?

Thank you very much
Jason

 

[hokhay]

Catalog for PCD-400A

 

[Oaklandishh]

My company does a lot of reading in of strain gauges.

we use the P3 strain indicator from Vishay/Micro-measurements.

Honestly working with Vishay is a pain because of their ridiculous lead times, but their products seem good.

The P3 is DC voltage and we can read consistently down to a resolution of 1 micro-strain using both 120 ohm and 350 ohm gauges.

What sort of resolution do you need? what sort of stability do you need?

 

[EdStainless]

Are you going to be testing at high frequency? Do you need very low level resolution?
If you are testing at near static conditions and want high sensitivity then the AC excitation is a good option.
Overall though I haven't seen enough difference to really matter.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[hokhay]

Thank you for all your reply.

Oaklandishh thanks for your suggestion. Could you tell more about what kind of tests your company do?1 micro-strain is what I am looking for, since the result will be used for comparison with FEA result. In term of stability, I do not have any clue for what to aim for. Could you give me a reference please? Could you also tell me the noise level that you get from the indicator?

EdStainless thanks for your reply. The frequency I expect from testing is less than 400Hz. I think that is not regard as high frequency, right? The testing will be both static and dynamic (normal frequency).

 

[Oaklandishh]

We do residual stress analysis.

I would say that usually the strain indicator doesn't fluctuate more than 1 micro-strain in the reading once the part has settled in a temperature controlled room.

If you want a readout frequency of 400Hz though I would look elsewhere than the P3 as I think it has something like 2Hz max readout using a computer and 1Hz using the instruments panel.

Here is the link if you are still interested though.

http://www.vishaypg.com/micro-measurements/instruments/p3-list/

I think the price is ballpark $2k?

 

[rb1957]

I thought static strain and frequency response required quite different set-ups ?

another day in paradise, or is paradise one day closer ?

 

[hokhay]

Thanks Oaklandishh. Althought P3 is not quite suitable for my need but it is good to know the level of fluctuation I May get from this kind of instrument.

Hi rb1957, could you tell me more of the different between static strain and frequency response set up please?

Thank you