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.
17 questions
2 votes
1 answer
255 views
Linear to log opamp transisor setup
I'm making a VCO for use as a module in a synth. The oscillator part is working fine. I also need to translate a 1v/oct voltage input to a log scaled voltage output in order to get the correct freq ...
- 173
1 vote
2 answers
305 views
Variable Analog Multiplier (Resistor Values, Concepts)
Is there a way to create a variable analog multiplier using conventional op amps? I've been trying to wrap my head around analog multipliers, and I haven't been able to come up with a reliable answer ...
0 votes
2 answers
166 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
0 votes
1 answer
251 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 + ...
- 450
6 votes
3 answers
659 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-...
- 456
4 votes
2 answers
369 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 ...
- 61
2 votes
3 answers
617 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 ...
- 169
17 votes
8 answers
3k 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
3 votes
2 answers
5k 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 \$ ...
- 53
0 votes
1 answer
289 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
0 votes
1 answer
119 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 ...
- 47
0 votes
4 answers
474 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 ...
user220456
3 votes
4 answers
638 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 ...
0 votes
2 answers
4k 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
0 votes
2 answers
892 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 ...
- 168