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Questions tagged [log]

For questions about logarithms (log axes such as on Bode plots, log scaling, etc.). Use "log-amplifier" for log amplifiers instead, and do not use for logging data. Consider also using "math" and/or a related plotting tag such as "bode-plot", if applicable.

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2 answers
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Circuit that offsets input voltage to exactly 0 V

I am looking for a (op amp) circuit to offset \$f(x)= \log(x)\$ always to zero. More comprehensible is the explanation on the x-y plot below. Basically, it is possible to offset the voltage with an ...
Andriy S's user avatar
0 votes
1 answer
131 views

Linear line on loglog plot

I'm trying to plot a -20dB/dec line on MATLAB but can't seem to get it correct. I know that a linear line in a loglog plot is actually an exponential curve in the linear scale. So writing a y = mx + ...
SM32's user avatar
  • 406
6 votes
3 answers
400 views

Log - Log Graph: Minor Increments Between Decades: 8 instead of 10 with spacing non-monotonically decreasing

Inolux uses (in its datasheet template for each of its LEDs) a log-log scale to depict the Relative Luminous Intensity, but it's not depicted in a manner that I've witnessed before. For example, IN-...
kando's user avatar
  • 437
4 votes
2 answers
256 views

Can I compress the dynamic range of ns pulses to better fit ADC range using log amp or mixer?

I have an experiment in which the signal I want to measure is a 1 ns pulse that occurs somewhere around 0-100 ns after a trigger. I want to digitize the pulses to extract the time they occurred and ...
argentum2f's user avatar
2 votes
3 answers
576 views

Valid or invalid logarithm operation?

Is the following operation valid or invalid? The question is to calculate receiver gain and this is one of the steps I got confused. The receiver sensitivity is given -45dBm and transmitted power is ...
eldenlord9394's user avatar
17 votes
8 answers
2k views

How can you turn perceived brightness (log scale) into a linear analog output using an LDR?

This question is not about how to make illuminance (in lux) a linear function of voltage! It's about linearly representing the human perception of brightness, which itself scales logarithmic to the ...
Niklas's user avatar
  • 298
3 votes
2 answers
4k views

How do you convert dBm to Vrms?

I'm trying to convert dBm to Vrms. The formula for dBm is \$ dBm = 10 * log(P1 / P0) \$ where P0 = 1mW so \$ +13dBm = 20mW \$ If I convert this to a voltage using the formula \$ P = Vrms^2/R \$ ...
timsweeney7's user avatar
0 votes
1 answer
238 views

How to calculate the 3dB frequency from an oscilloscope using a logarithmic sweep?

How do I calculate the 3 dB frequency from an oscilloscope reading using a logarithmic sweep? I made the mistake to use logarithmic instead of a linear sweep and now my data don't hold for the formula:...
User626's user avatar
  • 33
0 votes
1 answer
85 views

Logging and retrieving large bursts of sensor data from an Arduino

I was wondering, if I put an Arduino with a few sensors on let's say a water rocket to track acceleration and height and what not, how would I save this data? I'm assuming that I want to have a high ...
Christopher's user avatar
0 votes
4 answers
358 views

Values between log scales in a graph

I have a LED voltage vs current graph. The forward current is represented in a log scale. Suppose my value is 120mA. Where should I place my point and what would be my forward voltage with respect to ...
user avatar
3 votes
4 answers
519 views

Why does my diode log amplifier in LTspice not match theory?

I am trying to learn about analog multipliers, and I'm trying to implement one using a log-antilog design. I am currently having some difficulties with the log part because simulating an ideal ...
Paolo Celati's user avatar
0 votes
2 answers
3k views

Plotting a bode gain plot with the slope in Excel

I am not an expert in Excel, and therefore, I want to know if there is a way of including the slope (dB/decade) in a bode gain plot in Excel or any free software (that allows to first input the ...
William's user avatar
  • 71
0 votes
2 answers
783 views

I don't know whether HD44780 LCD is correctly initialized in Proteus

I'm trying to control an HD44780-based LCD in Proteus with 4-bit interface. The problem is that the simulation log gives me a series of messages, which I think means that I'm not sending the commands ...
vram's user avatar
  • 158
1 vote
2 answers
476 views

Potentiometer on max. resistance at lowest setting (off)

first question ever here: I'm struggling with a 10K log potentiometer in an EQ. When at lowest CCW setting it's the same value as on full CW pos. Is this typical when a pot goes bad or is that ...
jackaudioslave's user avatar
0 votes
1 answer
78 views

Understanding log-log axes

In below picture there are two graphs representing the function \$H(s) = s-z_1\$ (assume \$z_1=2\$ is a constant). The left graph has \$\omega\$ on x axis and \$\|H(j\omega)\|\$ on y axis. The right ...
AgentS's user avatar
  • 591