New answers tagged noise
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A couple of months ago we had an in-house EMC basic training, and these are my two cents to the subject.
Noise
Line noise can be generated by the source itself, and/or due to electrical and/or magnetic coupling. Electrical coupling is mostly caused by capacitive coupling to traces which experience high dV/dt, while magnetic coupling is more preponderant in ...
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Unfortunately, digital pots are not quite as 'design friendly' as their analogue counterparts.
The audio input voltages are AC, i.e. they alternate between + and - voltages. The voltages on the 3 digital potentiometer pins must fall within the Vdd-Vss range (in your case +5V and 0V). So the 'crackling sound' is probably due to the circuit only passing the +...
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I think your problem is that the audio signal needs to stay within the power supply voltage of the digital potentiometer(0-5V). Usually audio signals are centered around zero so when the signal goes negative, the potentiometer will clamp the voltage which messes with the audio. To fix this you would need to add a DC bias so that the signal stays within the 0-...
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The ISO7841 is the main cause of the noise, it specifies a typical output ripple of 100mV pk-pk, and its output frequency shifts with load, looks like in the ballpark of 30-100KHz,
ok, so your ADC following that has about a PSRR of about 80 decibels, so 0.1V * 0.0001 (-80 decibels ratio) = 0.00001V on the output, or 10uV pk-pk noise.
So your low pass's ...
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in the ADC there will be analog comparators, and opamps and probably DACs.
At really high frequencies, such as the 1 nanosecond RISETIME transients of MCU clocks coupling 1cm away into your ADC VDD, VREF, VIN(+) AND VIN(-), THE PSRR of circuits within the ADC becomes ???? zero??
Thus 10 quanta on trash coupled onto Vref ?may? cause a 10 quanta measurement ...
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Have you tried an adaptive filter? For instance, you could try a Least Mean Squares filter where the reference input is a separate piezoelectric sensor that detects the environmental noise exclusively.
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As others stated,the cause of the radio frequency interference (RFI) is likely separate inverters for a solar power system.
You can easily calculate values for an L-C filter for ~20 kHz region. About 10 nF and 6.3 mH, for example,should block most of that RFI coming over the wires. That said, you'd need an effective ground, e.g. a copper water pipe, to ...
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Some lighting systems use ‘high frequency’ ballasts in that range. Also may be noise from a switching power supply, or even a variable-frequency motor drive.
Use an AC power line filter to suppress it.
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I separated the motor from the steel table it was mounted to with some wood, and I also grounded the motor to a different ground from the DAQ's ground. Some interference still existed after this step, but the accelerometer's data was no longer being overwritten by the motor. The accelerometer will be mounted differently to the test fixture. The threads of ...
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to determine the broadband noise figure, which I've learned to simply describe as RNOISE, while not being confused by the low-frequency charges-bouncing-from-traps that produces 1/F random noise, you need to measure the RMS output from DC to about 1 decade above the 1/F frequency corner.
Thus the upper bandwidth will vary, because 1/F corners vary.
...
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Not having worked (professionally) at such low voltages, tho I have with experiments without good equipment to characterize the results, I'm concerned about
(1) trash entering the cable thru weaves in the copper braid ---- so use SOLID SHIELD coax cable.
(2) trash entering the cable, because either the shield or the center conductor are useful return ...
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Shielding efficiency (unless balanced) and triboelectricity are certainly concerns. Balancing mitigates shielding efficiency, and there are cables developed for microphone connections designed to reduce triboelectric effects.
But so is simple noise - Johnson noise, the thermal noise in any resistance.
(Shot noise, the statistical variation in current ...
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SNR is usually measured by taking the power of the signal and noise. Power is a well behaved robust estimator.
The peak is very fragile metric. Look at a noisy signal over different periods of time and you will record different peak levels. A better metric is the CDF or Cumulative Distribution Function, which tells you what fraction of time the signal ...
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Yes this is SNR and LOD are related.
As SNR=20log(Srms/Nrms). Rms value (root mean square) it's equal to the standard deviation (sigma).
So say "you need 3 sigma to mesure your signal" it's equivalent to say "You need a SNR of 20log(3)=10dB to measure your signal"
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It's a good question and there is a strong correlation between SNR and the ratio of errors /bit or BER and the steepness of the BER curve in dB per decade of BER. This curve can also be used with different data patterns and be used to find an asymmetric error in the detector or ISI or harmonic, random and periodic sources of noise.
Normally (no pun ...
answered May 6 at 7:13
Tony Stewart Sunnyskyguy EE75
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Yes, grounding the chassis GND of your notebook to the Protective Earth terminal in your wall socket often yields good results. Either use an additional wire with some suitabe connectors, or get a replacement external power module (black brick) that has the wall socket's PE connected to the output GND.
The EMI that you're observing may be RF or mains 50/60 ...
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That can be a lot of things, most including software problems, but in all likelihood:
This is a rate mismatch problem. Either, your software can't resample the 8 kHz to its internal sampling rate e.g. for codecs, or you think you're doing 8 kHz, where in reality you're doing 7.992 kHz or 8.008 kHz (or some other variation).
So, encoder expect 8000 samples ...
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LDOs have LARGE onchip transistors (FETs, usually, for low voltage drop) with large junction area and large gate-channel and drain-channel capacitances.
Assume 100 picoFarad across that transistor.
Given 1pF at 1GHz is =j159 ohms, then 100pF at 100MHz (Fring of MCU or switchreg) will be 16 ohms from output to input.
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If you take the SPICE model (or a real part) and sweep an AC current sink at the output you should be able to get a good idea of what the characteristics are over a range of frequencies.
At relatively high frequencies, the output capacitance (eg. 1uF ceramic plus any other bypass capacitors in your circuit) will dominate, and at DC, obviously, all the ...
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What you are expecting is never shown as this is the product of the spectral density of the load current times the spectral density of the source impedance.
Vs(f)= I(f)*Zs(f)
It is more useful to examine impedance ratios, Q and f-3dB and use a filter simulator to examine problems. I have found this way to be very effective ( Falstad's filter+Bode plots) ...
answered May 1 at 18:05
Tony Stewart Sunnyskyguy EE75
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You can always put an extra RC or LC filter between system supply and LDO regulator input to prevent ripples on LDO output load to couple back into system supply.
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But I'm actually more concerned with the noise being generated by the device fed by the LDO, and how much switching noise will end up feeding back into the system.
At low frequencies, this is called load regulation. In your datasheet, this is shown in the form of a DC transfer curve in figure 8:
At high frequencies (above ~100 kHz, depending on the ...
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It's just in the manual
:
4.1.8 Randomvoltagesource
The TRRANDOM option yields statistically distributed voltage values, derived from the ngspice random number generator. These values may be used in the transient simulation directly within a circuit, e.g. for generating a specific noise voltage, but especially they may be used in the control of ...
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