CONVERSION OF VIBRATION DB TO ACCELERATION

[Scotty]

Hello All

I have downloaded a LD824 sound level meter. I was using it of FFT
mode with an accelorometer and preamp. The downloded details and in
dB. I want convert this to acceleration.

The sensitivity of the Accelerometer is 100 mV/g.

Does anyone have a formula for this?

Cheers

Scott

[Asbjørn]

Post by Scotty
Hello All
I have downloaded a LD824 sound level meter. I was using it of FFT
mode with an accelorometer and preamp. The downloded details and in
dB. I want convert this to acceleration.
The sensitivity of the Accelerometer is 100 mV/g.
Does anyone have a formula for this?
Cheers
Scott

You have to give/get more information,
or preferably get hold of a vibration calibrator.
What was the reference for the dB values?
If that LD824's last calibration was with a microphone on the same
preamplifier,
there might be some hope if you know the sensitivity of that microphone.
(But I am on vacation)

If you had a vibration calibrator you possibly could calibrate the SLM to
show dB re. 1 micrometer/s2 (a0 = 10^-6 m/s2)
then 20 log(a0) = -120 dB, and 10 m/s2 would be 140 dB.
Then the measured acceleration a = 10^((La-120)/20) m/s2
where La is the measured acceleration level in dB re. a0.

Asbjørn

[Angelo Campanella]

Post by Scotty
Hello All
I have downloaded a LD824 sound level meter. I was using it of FFT
mode with an accelorometer and preamp. The downloded details and in
dB. I want convert this to acceleration.

I usually send the signal from an audio oscillator into the input
terminal of accelerometer amplifier and note the response. Then I set
the dB scale for a convenient value.

Ise any reference you want.

it's usually dB re one g RMS, or dB re one micro-g RMS.

The accuracy of your voltmeter that you use to measure the ac voltage of
the oscillator, and attenuator setting precision, becomes your accuracy
of measurement display.


Angelo Campanella

[Robert A. Hedeen]

Post by Scotty
Hello All
I have downloaded a LD824 sound level meter. I was using it of FFT
mode with an accelorometer and preamp. The downloded details and in
dB. I want convert this to acceleration.
The sensitivity of the Accelerometer is 100 mV/g.
Does anyone have a formula for this?
Cheers
Scott

Vey simple, assuming (i) you are using an ICP-type accelerometer with
a voltage (not a charge) output, and (ii) the SLM is correctly
calibrated for a 50 mV/Pa mike, as is usual for an L-D824:

1 g will produce 100 mV, but the L-D824, set to expect 50 mV/Pa,
thinks it is seeing 2 Pa. 1 Pa is 94 dB, so 2 Pa = 1g is 97 Pa. 3.16 g
= 107 dB, 10 g = 117 dB, 0.1 g = 74 dB, and so on.

By the way, how do you download a sound level meter?

Bob Hedeen

[Robert A. Hedeen]

On Wed, 11 Jul 2007 19:29:48 -0400, Robert A. Hedeen

Post by Robert A. Hedeen

Post by Scotty
Hello All
I have downloaded a LD824 sound level meter. I was using it of FFT
mode with an accelorometer and preamp. The downloded details and in
dB. I want convert this to acceleration.
The sensitivity of the Accelerometer is 100 mV/g.
Does anyone have a formula for this?
Cheers
Scott

Vey simple, assuming (i) you are using an ICP-type accelerometer with
a voltage (not a charge) output, and (ii) the SLM is correctly
1 g will produce 100 mV, but the L-D824, set to expect 50 mV/Pa,
thinks it is seeing 2 Pa. 1 Pa is 94 dB, so 2 Pa = 1g is 97 Pa. 3.16 g
= 107 dB, 10 g = 117 dB, 0.1 g = 74 dB, and so on.
By the way, how do you download a sound level meter?
Bob Hedeen

I'm thinking about it a little more. Actually, 2 Pa = 1 g ought to
read 100 dB, not 97.

Wait a minute - didn't we just finish this thread??

Bob Hedeen