Message 24224 in TECHNI.WW
From: G8MNY
Date: Mon, 15 Jun 26 06:33:00 Z
Newsgroups: TECHNI.WW
Subject: Eagle DB120 Sound Meter
Message-ID: <62484_GB7CIP>
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From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Correction Feb 16)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
The is a simple cheap sound meter.
____ PCB LAYOUT
CIRCUIT
capsule and VR1 calibrates 100R
oscillator Q1&2.
METER DRIVER oOff
To get a usable 40dB scale on a meter quite a lot of compression is needed.
This circuit uses an AGC approach. Transistors Q4, 5 & 6 from a power amp to
drive the double voltage doubler bridge D6-10 rectified load of the meter and
also provide AGC with D3 & D4 making an variable input attenuator.
VR5 set the AGC log action and diodes D1 & D2 correct for over compression to
get the very linear 40dB scale. VR4 is the main calibrate and VR3 is the
battery cal.
See my bul on "Sound Levels dBA dBB dBC".
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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