# 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.

15 questions
Filter by
Sorted by
Tagged with
85 views

### 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 ...
• 19
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 + ...
• 406
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-...
• 437
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 ...
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 ...
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 ...
• 298
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 $P = Vrms^2/R$ ...
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:...
• 33
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 ...
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 ...
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 ...
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 ...
• 71
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 ...
• 158
1 vote
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 ...