I'm trying to construct a dB meter for a school project.
I'm planning to find a mic capsule (could need some help choosing the right one) which then should have a switchable filter for the different weights, then amplified, and then I need to in some way measure the voltage and convert that to dB which can be displayed by some 7-segments.
So how can I convert the voltage to a dB measurement?
I'm planning to find a mic capsule (could need some help choosing the right one) which then should have a switchable filter for the different weights, then amplified, and then I need to in some way measure the voltage and convert that to dB which can be displayed by some 7-segments.
So how can I convert the voltage to a dB measurement?
Use a PIC processor, with an internal A/D converter.
Then you can do the math required and drive a LCD display ou 7 segment
At Microchip you can easily find a chip with 10 bit A/D and enough pins to do the job.
For programming the device you can do it in assembler or an high level language like C
Then you can do the math required and drive a LCD display ou 7 segment
At Microchip you can easily find a chip with 10 bit A/D and enough pins to do the job.
For programming the device you can do it in assembler or an high level language like C
Have a look at LM3914 from Ti. The data sheet will answer all of your questions.
http://www.ti.com/lit/ds/symlink/lm3914.pdf
http://www.ti.com/lit/ds/symlink/lm3914.pdf
Use the AD536.... It's a True RMS converter with db option (range 60 to 80 db) connect that to a DMM
You are right.... didn't check the prices... and however I did use this chip a long time ago I forgot how expensive it was... 🙁
But the cheapest versions are in the range € 16,- to € 30,-
Otherwise i'd advice to google for logarithmic amplifiers. Based on opams they do about 30 to 40 db lineair..
I'll second the advice for an external rectifier or log converter of some sort. If you work out the details, doing the rectification and log conversion in software makes it really hard to have much low level accuracy or dynamic range due to ADC drift and various offsets ahead of the ADC.
Another chip to try is the THAT 4316. With this and a simple micro controller with a 12 bit ADC, you can make a fairly accurate level detector, and end up with about 70dB of dynamic range if you're careful. There's an application note that shows you how to use it with its internal VCA section as a compressor ahead of the level detector to greatly expand the dynamic range of the detector as a whole. It's a bit cheaper than the above chips too...
Another chip to try is the THAT 4316. With this and a simple micro controller with a 12 bit ADC, you can make a fairly accurate level detector, and end up with about 70dB of dynamic range if you're careful. There's an application note that shows you how to use it with its internal VCA section as a compressor ahead of the level detector to greatly expand the dynamic range of the detector as a whole. It's a bit cheaper than the above chips too...
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