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| | | Low frequency measurement is critical for many industries. The petrochemical, machine tool, and paper industries use low frequency for both condition monitoring and process measurements. Other applications include slow speed agitators, cooling towers, semiconductor lithography, and structural testing. | | |
| | | 1,000 | | |
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| | | 100 | | |
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| | | 10 | | |
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| | | 1.0 | | |
| | | VIBRATION LEVEL (mils pp) (ips) (g) | | |
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| | | Low frequency measurements and low levels of vibclosely related. As shown in Figure 1, acceler | jration ; levels | | |
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| | | 0.1 | | |
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| | | 0.01 | | |
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| | | decrease at low frequencies. In order to have adequate | | |
| | | 0.001 | | |
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| | | voltage signals at the acquisition equipment, low frequency sensors have greater output sensitivity (usually 500mV/g) than general-purpose sensors. Additionally, the low-end frequency cut-off is improved (down to 0.1 Hz @ -3dB) in order to read slow speed vibration signals. | | |
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| | | 0.0001 | | |
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| | | 1 10 100 1K 10K 100K 1M Hz 60 600 6K 60K 600K 6M 60M cpm | | |
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| | | FREQUENCY | | |
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| | | Figure 1: Acceleration & Displacement Levels Relative to a Constant Velocity Level | | |
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| | | A | I Ul IICICI S II IUJI |JUI CHC I low-pass filter within the on-board amplifier electronics. Low frequency measurement usually involve low levels of vibration. The accelerometer's mechanical gain yield very high signal levels within the amplifier. High frequency signals could easily excite the resonance of the accelerometer and cause the amplifier to reach maximum voltage and saturate. This results in a "clipped" signal and distortion. Unless a high sensitivity accelerometer incorporates this protection, it could easily lead to obscured or false data. | | |
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| | | Wilcoxon Low Frequency Sensors: | | |
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| | | | | | | | | | | | | | Model | Style | Sensitivity | Low Freq | High Freq | Accel Range | | | | 793L | compression | 500 mV/g | 0.2 Hz | 2,300 Hz | 10 g peak | | | | 797L | shear | 500 mV/g | 0.2 Hz | 3,700 Hz | 10 g peak | | | | 799LF | shear | 500 mV/g | 0.1 Hz | 2,500 Hz | 10 g peak | | | | 799M | shear | 1,000 mV/g | 0.2 Hz | 2,500 Hz | 5 g peak | | | | | | | | | | | | | |
| | | < CO Q | | |
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| | | Note: Frequency @ ±3dB. | | |
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| | | W-15 | | | | |
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| | | 30 | | |
| | | WILCOXON RESEARCH, INC. • 1-800-945-2696 • TEL 301-330-8811 • FAX 301-330-8873 • EMAIL sensors@wilcoxon.com • WEB www.wilcoxon.com | | |
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