AGILENT 35670A

Supplemental Operator’s Guide

Section 18 : Measuring Frequency Response with the AGILENT 35670A

Frequency response functions characterize the behavior of systems to external stimuli. For mechanical systems, the stimulus can be a transient force such as an impact from a hammer, or a broadband stimulus, such as random excitation from an electrodynamic shaker. The response is usually motion of the system, measured with and accelerometer, velocity transducer, or displacement probe.

In either case the stimulus and the response measured with two channels of the AGILENT 35670A. The stimulus is usually measured on Channel 1, and the response is measured on Channel 2. The resulting frequency response is averaged to reduce noise and variance, and the result is displayed in a variety of formats that will be described in this section, including:

•Magnitude and phase

•Real and imaginary components (

•Nyquist Diagrams

The quality of the frequency response measurement is determined by how much of the response is due to the stimulus instead of being due to noise or other undesirable, unmeasured forces. Quality is described by coherence, which ranges from zero to one, where zero means none of the response is due to the stimulus. A coherence of one means that the response was entirely due to the stimulus

Measuring Frequency Response Using Impact Excitation

Refer to the section “Modal Testing Using a Hammer and Accelerometer” to measure frequency response using an impact as a stimulus. An impact provides broadband excitation, however the impact has a high peak to RMS ratio which tends to reduce measurement quality.

Measuring Frequency Response Using Broadband Excitation

Excite a system using the AGILENT 35670A built-in source to provide broadband excitation with low peak to RMS ratio and the best measurement quality. Use burst- random noise to eliminate window distortion and reduce leakage. The following instructions show how to set up a modal test with these example parameters:

electrodynamic shaker with amplifier

ICP force transducer with sensitivity of 8 mV/lb. ICP accelerometer with sensitivity of 10.2 mV/G wire sting to connect shaker to force transducer burst random excitation, uniform window frequency span of 800 Hz, 4 averages results viewed as log magnitude and phase

Set up the shaker

•Attach force transducer to structure

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Agilent Technologies manual Measuring Frequency Response with the Agilent 35670A, Set up the shaker
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Agilent 35670A specifications

Agilent Technologies Agilent 35670A is a prominent and versatile dynamic signal analyzer designed for various applications in vibration testing, structural analysis, and noise measurement. Engineered to meet the rigorous demands of engineers and researchers, the 35670A is especially valued for its advanced features and functionalities that facilitate detailed analysis and troubleshooting.

One of the primary features of the Agilent 35670A is its ability to perform real-time signal analysis. The instrument is equipped with a powerful processing engine that handles large amounts of data efficiently, providing fast and accurate results. This real-time capability is critical for dynamic testing applications, allowing engineers to monitor and analyze signals as they occur, thereby facilitating quicker decision-making and problem identification.

The Agilent 35670A employs advanced Fast Fourier Transform (FFT) algorithms, which provide high-resolution spectral analysis. This feature is essential for engineers needing to identify frequency components in complex signals, making it particularly useful in the fields of acoustics and mechanical engineering. The analyzer supports various types of measurements, such as magnitude and phase, enabling users to delve deeply into their data.

Another key technology embedded in the Agilent 35670A is its ability to perform multi-channel measurements. The instrument can connect to a variety of external sensors and testing devices, making it a flexible choice for users who need to analyze multiple signals simultaneously. This multi-channel feature is particularly advantageous in automotive testing, aerospace applications, and structural health monitoring.

The device also comes equipped with a user-friendly graphical interface, enhancing the overall user experience. The interface facilitates easy navigation and access to various measurement modes, settings, and data visualizations. Additionally, the Agilent 35670A supports automated measurements, allowing users to save time and reduce human error in repetitive testing scenarios.

Furthermore, the Agilent 35670A offers extensive connectivity options, including GPIB and USB interfaces, making it easy to integrate into existing laboratory setups and automated testing systems. This flexibility ensures that users can adapt the analyzer to their specific needs and workflow processes.

In summary, the Agilent 35670A stands out as a sophisticated dynamic signal analyzer that combines advanced signal processing technologies with user-friendly features. Its real-time analysis, multi-channel capabilities, and extensive connectivity options make it an invaluable tool for professionals in various engineering fields, dedicated to achieving precision in their analyses and solutions.
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