Digitimer
Digitimer - Hum Bug Noise Eliminator
ELIMINATE 50/60HZ NOISE AND HARMONICS WITHOUT FILTERINGELIMINATES ELECTRICAL INTERFERENCE

NO WAVEFORM DISTORTION• Simple 50/60Hz Sine Waves• No Frequency Loss

• Mixtures of 50/60Hz Harmonics• No DC Voltage Shift• Noise Spikes from Dimmers• No Signal Attenuation• Complex Noise from Fluorescent Lamps• No Phase Error

The Problem
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. Electricalinterference is notoriously difficult to remove without altering the original signal embedded within the noise.
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.
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
Faraday cages decrease the magnitude of environmental noise sources but this protection is often incomplete.
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
Developed by Quest Scientific and now manufactured and exclusively available from Digitimer Limited, the Hum Bug
provides a powerful technique to eliminate 50/60 Hz noise and harmonics from analogue signals without filtering.
The Hum Bug constructs a noise replica in real time and continuously subtracts this replica from the input signal. Itperforms this function in the presence of biological activity even when noise characteristics evolve over time.

Simplicity
The Hum Bug is a real-time device. Simply connect it between your preamplifier and any analysis or recording
equipment (oscilloscope etc.). It will automatically eliminate electrical interference while it lets the signal of interest
pass through unchanged. No settings or adjustments are required. The front panel switches are only used if youwish to bypass noise cancellation (BYPASS), stop the adaptation process (HOLD), or clear the noise replica(CLEAR).

Advantages
The Hum Bug is not a filter. It does not create phase delays, amplitude errors, DC shifts or waveform distortion. 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.

Environmental Noise• Power Lines• Power Supplies• Lights• Ground Loops

Noisy Signal

Clean Signal

Technical Overview
Theory of Operation: Principle operations of the HumBug are illustrated above. All functions occur inparallel as the signal passes in a direct analogue path between the input and output. The key innovation
developed by Quest Scientific is the ability to effectively isolate noise from an input signal even when noisecharacteristics are evolving and the frequency components of the noise and input signal overlap.
Frequency Response: Biological signals pass through the Hum Bug unchanged for frequency
components in the range of DC to greater than 500kHz.
Complex Noise: Electrical interference often generates a mixture of harmonics at multiples of 50/60Hz(e.g. 120Hz, 180Hz, 240Hz). The Hum Bug eliminates all harmonics with frequencies up to several kHz.
Therefore, even the complex spikes generated by dimmers and fluorescent lamps are eliminated.
Applications: The Hum Bug can eliminate 50/60Hz noise from virtually any analogue signal. It is equallyeffective at removing noise associated with inadequate grounding, ground loops and electrical pickup.
Common applications include noise elimination from signals recorded using microelectrodes, skinelectrodes (ECG, EMG, EEG), high gain amplifiers, magnetic sensors and audio equipment.

Specifications
Dimensions: 6.5" x 7.5" x 1.3" (W x D x H)
Weight: 2.75kg
Power: 115-240 VAC
Input Protection: 50V peak to peakMax. Input Signal: 5V average peak to peakMax. Noise Amplitude: 1V peak to peak
Frequency Response: DC to >500kHz
Noise Cancellation: 50/60Hz and harmonics to 4kHz
Controls: Bypass, Hold and Clear
Display: LED indicates changing noise levels

Manufactured by:Digitimer Ltd, 37 Hydeway Welwyn Garden City, AL7 3BE, UK
Tel: +44 (0)1707 328347 Fax: +44 (0)1707 373153
Email: sales@digitimer.com Web: www.digitimer.com