I am using Vishay 120 ohm Strain Gauges, (specifically EA-06-062AP-120) to try and generalize certain readings taken from aircraft engines. We have set up a small device to vibrate to simulate an engine on a small scale. The strain gauge is mounted to this device and the leads are then attached from the strain gauge terminals to a low noise signal amplifier and then to a computer based oscilloscope.
Here is a link of a sample output image taken at 16.7 Hz. The small wave is coming from a signal generator while the larger wave is from the strain gauge and amplified by low noise amplifier.I understand that a strain gauge is in essence a resistor. However this setup is just going through a low noise amplifier, and not a wheatstone bridge. I understand what I would probably expect if I went through a wheatstone bridge followed by the amplifier, but this is different. So is what I am looking at in that graph the value of the resistance of the the strain gauge with respect to the signal from the signal generator? Can anyone help explain to me in english what exactly I am looking at on this oscilloscope screen. What is the significance of the Vrms value if it is a resistance? And I know the -24.8dBm is in relation to the gain, but what does it mean?
The signal generator is at 16.7 Hz with a setting of 1.5V per division, while the signal from the strain gauge is a setting of 50 mV per division.
On a different note, the amplifier has a gain based on the resistance value of a particular potentiometer mounted to a circuit board. Is there a way to measure the resistance of that potentiometer while it is mounted to the circuit board? Is it acceptable just to use an ohmmeter across available terminals?
Any help is much appreciated.