About issues caused by electrical noise, or improving the Signal/Noise ratio of an analog circuit.

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Why does a 12V DC applicance generate 50 Hz power line noise in nearby EEG recording

A layman's question: I am recording electroencephalographic signals (EEG) in a shielded cabin. In this cabin, I am also operating an additional electrical device powered by 12V DC (an eye tracker). ...
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1answer
43 views

Suppressing BLDC Motor noise? Is it radiated or a grounding issue? [on hold]

I have a BLDC motor that rotates an imaging assembly(ultrasound) and alot of PWM noise can be seen in the resultant image produced. If I play around with the RX line that carries the imaging signal ...
29
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7answers
5k views

How can “purely” electrical circuits emit sound?

Moving membranes or piezoelectric materials obviously produce sound waves, but how can "purely" electrical circuits such as transformers or DCDC choppers (and others) often have an audible noise? Is ...
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3answers
108 views

How to isolate processor noise

I'm designing a board that consists of a dspic33F, responsible for running a noise reduction algorithm and compressing audio with a Speex library, and an audio codec connected to an electret ...
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2answers
117 views

Do vias introduce more noise to signal

If I have a small signal, does routing it through vias to different layer introduce any significant noise on the signal compared to routing it within same layer without any vias? Considering all other ...
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2answers
54 views

Ideas for troubleshooting a noise generator on a PCB

I am building an electronic "dice" that uses an ATTiny84 to sample avalanche noise from a 2N2222 in reverse-bias and generate random numbers, which are then displayed on 2 7-segment displays. When I ...
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5answers
108 views

Can a proximity sensor read through fabric?

I am trying to build an arduino project with the following requirements: Proximity sensors detect human presence and its distance The sensors are hidden behind fabric Range has to be 1-3 meters or ...
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2answers
103 views

Inconsistency of ADC output

I am having an issue with my ADC output. I am using: 12-bit ADC integrated in a MCU 3.3V voltage reference. Power supply of MCU, ADC and ADC voltage reference sharing the same voltage rail(3.3V) ...
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1answer
75 views

Homework: Noise in a circuit [closed]

I had this problem in a homework assignment: If the noise in a 5 V voltage line and ground for a five volt circuit is of the order of 10 mV, for a first order system, how many time constants will ...
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2answers
52 views

Shielding for Load cells

I am currently having a lot of trouble with noise being picked up by load cells. The strain gauges on the load cell are configured in a full-bridge pattern. In a noiseless environment (ie far away ...
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1answer
49 views

Statistical noise measurement

Is there an accepted measure of noise in a data set? I am taking a series of reading from an ADC, which follow a trend (they are not random data points). However, they generally lie above and below ...
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1answer
111 views

What are these pulses?

To continue of this question... I figured out the main problem and now I have an odd problem. at first, let me to put the codes. "Main.c": ...
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0answers
80 views

Can this op amp circuit easily be modified to provide differential input?

I have a "noisy ground" problem which seems to be essentially the same as the one described in this old post: Ground loop? Switch mode power supply noise The solution (as provided in the answers to ...
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2answers
110 views

Are all USB “audio adapters” DAC's? Can USB ports be used for analog output?

Kind of a weird question.. Background: My motherboard has started producing weird static(buzzing) noises on the audio output(3.5mm jack), it's not noticeable when using headphones, but on speakers it ...
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2answers
338 views

Noise at 2^n transitions

I am sampling a video signal from a linear imager. I noticed when the illumination is just at the intensity when the ADC increases by another MSB bit at the output, the noise occurs. That is, when ADC ...
2
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2answers
304 views

I/O series resistor

I've read that digital I/O pins should have a resistor in series in order to limit noise. Should one also use such approach when interfacing with the I/O pins of an arduino, or is that already done on ...
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2answers
72 views

Switching regulator PCB layout

I'm putting together a buck regulator (first time around) based on the lm2374 chip. TI provides gerbers of a recommended layout for this chip family, but my configuration differs a bit. I've read up ...
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1answer
50 views

Static in earphones when scrolling with mouse [closed]

Why do I sometimes hear faint static in my headphones when I scroll with my mouse? I have noticed this on multiple(4) computers, with Windows 7 and 8. Does anybody else notice this? It happens when I ...
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1answer
59 views

instrumentation amplifier output noise

I have a low level DC signal from a thermopile sensor of 0-9.1mV with 7uV increment. I feed this to an INA114 instrumentation amplifier with gain of 550 to get 0-5V output. I tried introducing RF ...
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3answers
81 views

SPI on long wires with current control

I need to control a 5V CMOS SPI device in my car, but the microcontroller distanced by 5 meters of wires. I googled that standard solution for my problem is differential lines like RS485. But I don't ...
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2answers
161 views

Noise control in op-amp circuit design by using low spec op amps

I have a rather strange problem. I have a breadboard circuit on a double sided PCB with plenty of ground plane and a good well decoupled power supply. I am amplifying a small medium frequency signal ...
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1answer
73 views

Best method to eliminate alternator whine from a 12V line?

I've purchased a Miccus Mini-Jack Rx BlueTooth audio receiver. This device will accept a bluetooth signal from my phone and output it to a headphone jack that I plug into the AUX-In on my car stereo. ...
4
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2answers
473 views

Why does reversing the oscilloscope probes cause ringing in the signal?

I am measuring a PWM signal in an oscilloscope using probes with a 1X and 10X switch (active?). I'm measuring across a resistor which is in series with an LED which is driven by an NPN 2N3904 ...
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3answers
653 views

Does a pin jumper adds noise?

When designing a PCB, is it sensible to use a pin jumper in the pathway of a small current signal (around 0.8 uA) or could there be issues with noise? I would use the jumper to select between ...
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3answers
291 views

Ferrite bead position

I wish to use some extra power supply filtering for my DAC, ADC, CPLD and OpAmp devices. In this question I got the point about the global locations for ferrite beads. If I understood correctly, the ...
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1answer
95 views

How to calculate RMS of total noise from digital Oscilloscope (FFT)?

Only the red channel is in consideration. The yellow curve is not relevant, which is only another channel of the oscilloscope. The image above was captured from a digital oscilloscope. The vertical ...
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2answers
182 views

Replacing a FET to avoid the body diode (audio switching)

Here is a circuit I've found online for switching a guitar signal, it uses a mechanical relay in order to rout the signal through a sound processing unit or around it, bypassing the circuit. ...
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3answers
83 views

Signal to noise ratio for a non-physical property

The signal to noise ratio for a voltage, current, or power is easy to understand, but how do I calculate the SNR when the signal is not a physical property, but instead an abstract quantity? I'll try ...
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1answer
77 views

Weird samples from SAR ADC

I am playing around with some SAR (Successive Approximation) A/D-converters. I have made a test circuit where I have a 16-bit DAC from Texas Instruments (R2R-based) and an 16-bit SAR ADC from Analog ...
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1answer
131 views

NRF24L01+ false detection

I use a NRF24L01+ module configured for receiver, 3-bytes address, 1-byte CRC, 1 Mbit/s, channel 2402 MHz, 2 pipes listening. Addresses are non-trivial (0x525443 and 0x4d4252). But when transmitter ...
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1answer
127 views

Can I set thresholds for 74HC14N (6 NOT gates)? and use as schmitt trigger

I'm trying to convert sine-like wave from IR sensor(quadrature wheel encoder) into square one. Can I make it with 74HC14N(set some fancy RC configuration) or should I use op-amp configuration to be ...
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2answers
70 views

Low noise amplification - Op Amps vs Transistor based amplifiers

Whats the best amplification strategy to use for something requiring very low noise like an EEG (brain wave detecting)? Efficiency isn't really an issue. Op amps with high CMRR are expensive, and ...
0
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1answer
57 views

Current Monitors for Avalanche Photodiodes

I've come a across a document by Linear Technologies that suggests several circuit schematics to interface with an Avalanche Photodiode (APD). They are referred to as current monitors and placed ...
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4answers
87 views

High input impedance devices - induced noise sensitive

I am currently reading about 4-20mA current loops and the reason we use them .As stated there , using voltage to transmit signals we get voltage drops over long cables due to cable resistance. We ...
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1answer
157 views

Any tricks to generate triangle wave to add to analog signal for oversampling?

I want to increase the effective resolution of the ADC by oversampling and decimation. Unfortunately the signal I'm realing is too clean, so I would like to add a bit of artificial noise (1LSB peak to ...
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2answers
112 views

Power supply noise caused by external heat pad

I have a circuit that switches a 50W Sunbeam heating pad via a relay (for regulating temperature). My circuit is driven by a 5v AC/DC switching converter. The AC input to the power converter is shared ...
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2answers
108 views

Simulating accelerometer noise

I would like to create a software simulation of an accelerometer (MPU-6000). As part of that simulation, I need to model the noise on the accelerometer signal. According to the datasheet of the chip, ...
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1answer
59 views

Does NI Multisim simulates op-amp input and output noise?

I just created a circuit with AD620 in-amp and I'm worried that there is not enough noise. I wonder if Multisim simulates advanced op-amp/in-amp properties, like input noise and such? I mean, if I ...
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3answers
222 views

the causes of Fading of signals

I have read about fading of signals , and I have notice that the major cause of fading is multipath , but I have ask myself , what about attenuation , noise and free space loss , all of these make the ...
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1answer
62 views

How much is the noise of a multiplexer for analog inputs?

I have 4 sensors, each have with two differential output (S- and S+) that I need to use in a differential amplifier (with a gain equals to 1000 in my case). The difference between S- and S+ is ...
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0answers
92 views

Demanding design on bandpass filter/ Notch filter with gain

I have posted a related question before, which can be found here: Very low noise high pass filter design However, since a different stage is to be considered, I started this new post. We are not ...
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4answers
289 views

Very low noise high pass filter design

We are trying to design a high pass filter, which mainly goals are: very low noise. Low noise is the first concern. suppresses 1kHz by around 50dB and passes 2kHz. Gets rid of DC Dont care on other ...
0
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1answer
211 views

How to filter low frequency noise on power supply from ChipCorder?

I've built a circuit using an ISD4003 ChipCorder, which is an IC for recording and playback of audio (in a telephone answering machine, for example). I've written code to send the SPI commands to ...
2
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3answers
352 views

Fighting overshoots/undershoots using ferrite beads does not help?

I posted relative problem a while ago here but we came to conclusion that the overshoots were just artifacts. Later, when I extended the signal lines, the overshoots increased and were about 2V of ...
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1answer
141 views

Will motors cause more noise when connected to a ground plane instead of directly to batteries?

I am making a small robot using an Arduino and two servo motors. There are two ways that I can provide power to the motors: 1) Run power and GND wires from the battery holder to the motors, then ...
0
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1answer
39 views

Is the Delay in Strain Data Due to Capacitance?

I have designed a sensor board which gives a strain o/p based on wheatstone bridge principle(change in stress is measured through change in resistance). But the starting value is not at zero level,it ...
4
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1answer
114 views

How can I track where this 471kHz noise is coming from?

I'm new to EE in general and I just received my first oscilloscope (Rigol DS1102E). Anyway, I'm building an audio circuit using an Arduino Micro and the infamous ...
2
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1answer
309 views

Clean DC power design for very high precision circuit

We have been designing a very high precision control circuit for quite a while. And we are thinking to make it much easier to use, which is to get rid of the Lab DC Sources and use AC to DC switching ...
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1answer
103 views

Curious noise on FPGA Microcontroller connection

I have the following setup: An FPGA eval board has a daughterboard with pin headers connected to it. From these headers I have connected 16 ~10 inch 24-gauge wires to feed a bus to a TI OMAP-138 ...
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2answers
149 views

Filter 50Hz hum picked up by the oscilloscope

I am measuring huge 50Hz oscillations on my oscilloscope, but I am not entirely sure the probe is generating those by behaving like an antenna (an ADC at the same point gives stable values but it's ...