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Capture Peak Strain Gage Fluctuation For Shotgun Chamber Pressure Measurement

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Silver_Is_Money:

--- Quote from: Kleinstein on December 20, 2023, 10:23:44 am ---Definitely DC as the relevant signal is only short, like a few ms at most. AC drive is a thing if one cares about long time drift and 1/f noise from the amplifier.
For the amplifier I would consider a normal single ended amplifier and have a floating (e.g. battery) to provide the bridge drive. It is about getting lowest noise and the scope input directly is not really made for such low impedance (e.g. 350 ohm for common strain gages).

--- End quote ---
Would a precision multimeter with peak voltage capture capability be an overall better choice in this application than an Oscilloscope?  And if so, are there any suitable multimeter recommendations?

bdunham7:

--- Quote from: Silver_Is_Money on December 20, 2023, 09:04:30 pm ---Would a precision multimeter with peak voltage capture capability be an overall better choice in this application than an Oscilloscope?  And if so, are there any suitable multimeter recommendations?

--- End quote ---

No, both not fast enough and it is going to be a lot handier to see the overall pressure pulse not just a number.

Silver_Is_Money:

--- Quote from: bdunham7 on December 20, 2023, 11:52:41 pm ---No, both not fast enough and it is going to be a lot handier to see the overall pressure pulse not just a number.

--- End quote ---

By your statement regarding both not being fast enough, does this imply that neither a good Oscilloscope nor a good multimeter will reliably capture the moment and magnitude of peak pressure as seen by the strain gage?  If so, then my quest is stillborn.

bdunham7:

--- Quote from: Silver_Is_Money on December 21, 2023, 12:32:12 am ---By your statement regarding both not being fast enough, does this imply that neither a good Oscilloscope nor a good multimeter will reliably capture the moment and magnitude of peak pressure as seen by the strain gage?  If so, then my quest is stillborn.

--- End quote ---

No, the 'both' refers to the DMM being both not fast enough and not as handy.  I guess I could have written a bit more clearly.  The scope will be more than fast enough, your only worry would be the response time of the strain gauge.  A fast DMM will register a peak 250µs long, also known as 1/4000 of a second.  An entry level scope will register peaks shorter than 10ns, or 1/100,000,000 of second.

joeqsmith:
Say you have an 8-bit scope. 2^8 is 256 discrete levels.   Say you have a peak chamber pressure of 60ksi.  60000/256 giving you a resolution of 230PSI.   

Looks like you only need a ms or so of data.  Even a us (0.000001 second) resolution may be good enough.   You may be better off with a data acquisition system that could give you a higher pressure resolution.   You would need to provide details. 

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