How to use an analog umeter to read dB ?

[pierino]

dB meter

Hi
can someone tell me how to use an analog umeter to read dB - I am sure it can be done , maybe w/ some opamps or some passive components...!?
Any schematic(s) would be nice
THANKS
- Pierino

 

[echo47]

dB meter

An analog VU meter is simply an AC voltmeter with a dB scale painted on it.
Do you need something fancier than that?
Example: **broken link removed**

 

[MAKeller]

Re: dB meter

Take a look at the Linear IC by National Semiconductor.
The series LM3914-LM3916.

MAKeller

 

[seadolphine2000]

dB meter

check this

**broken link removed**

 

[pierino]

Re: dB meter

An analog VU meter is simply an AC voltmeter with a dB scale painted on it.
Do you need something fancier than that?
Example: h**p://www.sifam.com/vuppm.lasso

Thank you for your reply
What I want to make is to be able to read dB on a microvolt (or mV) meter . I will then make a new scale for the meter, but the point is to interface somehow the voltmeter to read dB. Maybe I need a log opamp amplifier .. or something similar !?
Thanks

 

[echo47]

dB meter

You can convert your AC signal to DC and then feed it into a logarithmic converter circuit. Try searching National Semiconductor web site for application notes containing keywords such as log, logarithmic, converter, generator, amplifier.
**broken link removed**

Here are a few examples:
**broken link removed**
**broken link removed**

 

[Kral]

Re: dB meter

Here are some suggestions if your intention is to construct a true "VU" meter:
~
The meter must repond to average, not peak.
~
Ballistics are important. The meter must have a response time of about 300 milliseconds.
~
VU meters are not necessarily linear in db, but if this is what you want, you must use some kind of Log converter, as Echo47 suggests.
~
Regards,
Kral