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The
Problem
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Signals recorded using biological sensors and other high impedance devices are often contaminated with 50/60
Hz noise
corrupting the content of these signals and
degrading the quality of subsequent data analysis.
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Electrical interference is notoriously difficult to remove without altering the original signal imbedded within the noise.
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In theory, proper attention to ground and appropriate shielding can eliminate electrical interference. In practice, noise remains a frequent and distressing problem in
many laboratories.
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Noise may come and
go for no apparent reason and may appear during critical phases of data collection. The effort required to maintain noise at an acceptable level is both time consuming and frustrating.
The
Traditional Approach
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Faraday cages decrease the magnitude of environmental noise sources but this protection is often incomplete.
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Notch or comb filters are occasionally used to suppress 50/60 Hz noise and harmonics but these filters will distort the input waveform if the frequency components of the signal overlap with the filtered frequencies.
A
New Solution
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Quest Scientific has developed a powerful new technique to eliminate 50/60 Hz noise and harmonics from analogue signals without filtering.
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The Hum Bug constructs a noise replica in real time and continuously subtracts this replica from the input signal. It performs this function in the presence of biological activity even when noise characteristics evolve over time.
Simplicity
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The Hum Bug is a real-time device. Simply connect it between your preamplifier and any analysis or recording equipment (oscilloscope
etc.).
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It will automatically eliminate electrical interference while it lets the signal of interest pass through unchanged. No settings or adjustments are required.
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The front panel switches are only used if you wish to bypass
noise cancellation (BYPASS), stop the adaptation process (HOLD), or clear the noise replica (CLEAR).
Advantages
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The Hum Bug is not a filter. It does not create phase delays, amplitude errors, DC shifts or waveform
distortion.
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It effectively eliminates 50/60Hz noise and harmonics without altering the frequency characteristics of the input signal even when these frequencies overlap with noise components.
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