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Quest Scientific Hum Bug, Reference Manual

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Quest Scientific 

Hum Bug 

REFERENCE MANUAL

 

 

 
 

 

 

 

CONTENTS

 

Introduction.................................................. 3 

Theory Of Operation.................................... 4 

Installation ................................................... 6 

Controls ....................................................... 7 

Input Signal ................................................. 7 

Noise Generated By Monitors ..................... 8 

Sources Of Complex Noise ......................... 9 

Adaptation Rate........................................... 9 

Front Panel................................................ 10 

Back Panel ................................................ 11 

Trouble Shooting ....................................... 12 

Specifications ............................................ 18 

Warranty And Contacts ............................. 18 

Summary of Contents for Hum Bug

Page 1: ...NTS Introduction 3 Theory Of Operation 4 Installation 6 Controls 7 Input Signal 7 Noise Generated By Monitors 8 Sources Of Complex Noise 9 Adaptation Rate 9 Front Panel 10 Back Panel 11 Trouble Shooting 12 Specifications 18 Warranty And Contacts 18 ...

Page 2: ...Page 2 Hum Bug Reference Manual Quest Scientific ...

Page 3: ...oise without any need for adjustment The Hum Bug is not a filter It is a new class of instrument capable of eliminating electrical interference from analogue signals without creating phase shifts frequency loss amplitude errors DC shifts time delays or digital distortion It effectively eliminates 50 60 Hz2 noise and harmonics3 without altering the frequency characteristics of the desired signal4 e...

Page 4: ... 5 to 10 seconds under ideal conditions but is slower when low amplitude noise is dominated by ongoing physiological activity and or noise harmonics are greater than 1 kHz Therefore the noise replica may lag behind if the noise characteristics suddenly change Under these conditions some noise will transiently appear on the output while the Hum Bug adapts to the new characteristics The major advant...

Page 5: ...Hum Bug Reference Manual Page 5 Quest Scientific ...

Page 6: ... operating mode During your initial evaluation of the Hum Bug it is a good idea to turn off any computer monitors in the vicinity of your recording setup This will eliminate possible confusion between 50 60 Hz noise and any additional interference associated with your monitors See the section on monitor noise for more details After an initial warm up period of approximately thirty seconds the Hum ...

Page 7: ... Pushing it will clear the noise replica and force the Hum Bug to generate a new noise replica from scratch In effect this causes the Hum Bug to immediately forget the noise waveform This function is seldom necessary since the Hum Bug automatically adapts to changing noise conditions INPUT SIGNAL The Hum Bug will operate on analogue signals originating from virtually any laboratory equipment inclu...

Page 8: ...erference is the same as the power mains so it will be eliminated by the Hum Bug The second form of interference referred to as refresh noise is generated each time a monitor refreshes the image displayed on its screen The frequency of this interference will depend on the video mode assigned to the monitor In most cases it will differ from the power mains and will not be recognized as noise by the...

Page 9: ...ncy response is acceptable will depend on your application Feel free to consult Quest Scientific for more information ADAPTATION RATE The Hum Bug adapts to changing noise characteristics in the input signal Under normal conditions these characteristics evolve slowly and the Hum Bug is able to maintain effective noise elimination However noise will appear in the output signal following a sudden cha...

Page 10: ...lowly over time However touching a manipulator approaching the electrode or lifting the electrode from the experimental preparation can cause additional but transient noise on the recorded signal Using HOLD during these manipulations will keep the Hum Bug from chasing the transient noise As a result effective cancellation of ongoing noise can resume immediately after the manipulation is complete ...

Page 11: ...Hum Bug Reference Manual Page 11 Quest Scientific BACK PANEL ...

Page 12: ...t to the expected behavior described for each procedure Step One Set up your equipment in a manner similar to the illustration shown below The objective is to simultaneously view the input and output of the Hum Bug on different channels of an oscilloscope while recording a noisy signal This description assumes that you are recording neuronal activity using a micropipette but a similar procedure co...

Page 13: ...ed as the noise replica grows to the required size When adaptation is complete the Indicator should be off Toggle BYPASS mode on red LED and off green LED to observe the signal with and without noise cancellation Compare the input and output signals You should find that the primary signal of interest is not modified by the Hum Bug Step Four Observe the Hum Bug adapt to changing noise conditions On...

Page 14: ...us on different types of abnormal Hum Bug behavior The tasks outlined in each section are designed to help you identify the specific cause of abnormal behavior in your Hum Bug A The Hum Bug fails to operate 1 No LEDs are illuminated on the panel switches and the indicator does not illuminate when you push clear Check that the power switch is on Check that the power cable on the back panel is pushe...

Page 15: ...ce Perhaps the peak to peak level of noise is too large for the Hum Bug to completely cancel If so the indicator will continue to flash red Connect the input signal of the Hum Bug to an oscilloscope and determine the noise amplitude The Hum Bug cannot cancel noise greater than 1 Volt peak to peak If your noise levels are higher than this limit you may have to reduce the gain in your preamplifier P...

Page 16: ...put is grounded but much larger than expected when an input signal is connected to the Hum Bug Perhaps the grounding of the Hum Bug and associated equipment is the problem See section D1 Are you connecting the Hum Bug to an unusual piece of equipment If so check the output impedance of the device Although the Hum Bug will adapt to a wide range of input characteristics a signal source with a very h...

Page 17: ...und wires will make inappropriate connections between grounds in your setup and the grounds in the power mains Check your cables to make sure that the braided shield is connected to the ground ring of the BNC connector on both ends If you have tried the suggestions outlined above and still have problems or questions please contact Quest Scientific ...

Page 18: ... Hz to 4 kHz Controls BYPASS halts noise cancellation by routing input directly to output HOLD suspends adaptation to evolving noise characteristics CLEAR clears the noise replica Display LED indicates changing noise levels GREEN decreasing amplitude of the noise replica RED increasing amplitude of the noise replica QUEST SCIENTIFIC 1164 West 21st Street North Vancouver BC Canada V7P 2C8 Voice and...

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