Question

Question: I am using Endevco® model 2771C series in-line remote charge converters for an experimental modal analysis application. How can I determine charge converter phase response at 1 Hz?

Answer

For the benefit of readers who may be unfamiliar with in-line remote charge converters, such as the Endevco® model 2771C series, they are commonly specified for the conversion of high-impedance piezoelectric charge mode accelerometer output into low-impedance voltage output. A main advantage of using remote in-line charge converters is their compact size, which allows them to be placed directly in-line with the cable.

Within a typical experimental modal analysis application, several accelerometers are strategically placed at various points within the structural body to be characterized. The corresponding responses of the different points to structural excitation of the test article can then be analyzed. There are two typical plots for Endevco® model 2771C charge converters, used to provide phase response data for all specified dash numbers (dash numbers represent different gains).

Figure 1 shows the phase plot for models 2771C-01 and 2771C-1. Figure 2 shows the phase plot for the model 2771C-10. The phase angle at 1 Hz for models 2771C-01 and 2771C-1 is -163°, as per Figure 1. The phase angle for model 2771C-10 at 1 Hz is -123°, as per Figure 2.



Note: If the application requires high sensitivity with minimal phase shift at low frequencies, please consider the use of variable capacitance (VC) accelerometer technologies, such as the Endevco® model 7290E. The phase shift will be almost 0 degrees at 1 Hz.