Frequency Analysis

[taraka]

Hi, Thank you,May be my computer(labview) was too slow and DAQ was fast i will change my computer and will check again.

Again i have a small question how to caluclate power at piezo stack by using oscilloscope in labview...... 

[johnsold]

Power at the piezo stack will be difficult to measure. To measure power in general you need to measure both the voltage and the current with sufficient timing resolution to determine the phase shift between them. Measuring phase shift near a resonance can be tricky, especially in a case like this where the temperature may be changing and the pressures may change the density enough to shift the resonance slightly. 

Without knowing more about the physics, I cannot estimate the necessary sampling rate but I suspect that rates > 1MHz would be required for good results.

Lynn

[taraka]

Is it possible to measure Voltage at piezo stack using oscilloscope in labview.

[johnsold]

Maybe. What are the voltage ratings of the piezo stack? Piezo devices may have ratings from less than a volt to kilovolts depending on the design and application. 

Lynn

[taraka]

May be its in +15 volts we are using piezo PZT5A

[johnsold]

I do not see that you have reported what DAQ device you are using. Does it have a range which will accept a 15 V signal?

Lynn

[taraka]

We are using NI PCI-6024E

[johnsold]

The highest voltage range for that device is +/-10 V. So it is not suitable for direct measurements of the voltage on the piezo stack.

Because piezo devices look like capacitors to the electrical circuit, I would need details of the device chracteristics and of the driver circuit and anything else attached to it before being able to make a recommendation on a voltage divider.

Lynn

[taraka]

the piezo we are used has a reference voltage of PZT27-V(Z) Nom.(V) Reference Voltage :  27     Maximum Operating Temp (шC) :  185

PZT27 is a type of piezoelectric ceramic crystal material with good coupling factors, good charge coefficients, high Curie temperature, low mechanical quality factor and low temperature coefficients. It is more sensitive, but has slightly higher temperature dependence.