🚀 go-pugleaf

In article <cstevens-0109951235590001@cstevens.advtech.uswest.com>
           cstevens@uswest.com "Clarke Stevens" writes:

> In need some instrumentation microphones and accelerometers for some
> multi-channel (16) DSP tests I am running.  My current choices seem to be
> B&K and HP's DSA brand.  Both of these are quite expensive.  Does anyone
> know of some less expensive options that would meet the following
> criteria?
> 
> * Flat frequency response from about 30 Hz to about 8 kHz or better
> * Consistent quality
> * Battery powered power supplies/amplifiers
> * BNC output
> * Reasonable environmental tolerance (i.e. mounted to a vehicle in the hot sun).> 
> Thanks in advance,
> Clarke

Knowles Electronics make good quality electret microphones inserts. I
got a couple of samples from their UK office, although I haven't used
them yet. The acoustics division of the firm I work for uses them a lot
for spectral analysis inside noise reducing headsets and the like. They
are quite inexpensive at about #12 each. I don't have the data with me
here, but their response is flat to over 10 KHz, as I recall. You'll
have to attach your own connector and battery, though. Knowles is a US
company, and I don't have their US address with me, I'm afraid.

Leon
-- 
Leon Heller, G1HSM                | "Do not adjust your mind, there is
E-mail leon@lfheller.demon.co.uk  |  a fault in reality": on a wall
Phone: +44 (0)1734 266679         |  many years ago in Oxford.

In article <cstevens-0109951235590001@cstevens.advtech.uswest.com>
           cstevens@uswest.com "Clarke Stevens" writes:

+ In need some instrumentation microphones and accelerometers ...

I see you've posted to several newsgroups, but I suggest that the
best relevant experts on the net are to be found in
alt.sci.physics.acoustics.  If you can't get this group let me know
and I'll post a query for you.

-- 
Tony Woolf  (tony@howl.demon.co.uk)

In article <cstevens-0109951235590001@cstevens.advtech.uswest.com>
           cstevens@uswest.com "Clarke Stevens" writes:

+ In need some instrumentation microphones and accelerometers for some
+ multi-channel (16) DSP tests I am running.  My current choices seem to be
+ B&K and HP's DSA brand.  Both of these are quite expensive.  Does anyone
+ know of some less expensive options that would meet the following
+ criteria?
+ 
+ * Flat frequency response from about 30 Hz to about 8 kHz or better
+ * Consistent quality
+ * Battery powered power supplies/amplifiers
+ * BNC output
+ * Reasonable environmental tolerance (i.e. mounted to a vehicle in the hot sun).+ 
+ Thanks in advance,
+ Clarke
+  
+ -------------------
+ J. Clarke Stevens
+ cstevens@uswest.com
 
I'm re-quoting this and posting also to alt.sci.physics.acoustics,
because I think that's where the experts mostly are.  

Follow-up to this posting is set to alt.sci.physics.acoustics only.

-- 
Tony Woolf  (tony@howl.demon.co.uk)

cstevens@uswest.com (Clarke Stevens) wrote:

>In need some instrumentation microphones and accelerometers for some
>multi-channel (16) DSP tests I am running.  My current choices seem to be
>B&K and HP's DSA brand.  Both of these are quite expensive.  Does anyone
>know of some less expensive options that would meet the following
>criteria?

>* Flat frequency response from about 30 Hz to about 8 kHz or better
>* Consistent quality
>* Battery powered power supplies/amplifiers
>* BNC output
>* Reasonable environmental tolerance (i.e. mounted to a vehicle in the hot sun).

I use KE4-211-2  (Part #172280) omnidirectional electret condenser
capsules from

SENNHEISER ELECTRONIC KG 
Am Labor 1
D-30900 Wedemark
Germany

Phone: +49 5130 6000
Fax:       +49 5130 6312

They are specified by the manufacturer to have a frequency response
from 20Hz to 20kHz (40Hz to 10kHz within +/+ 2.5 dB). The response
above 10 KHz is not shown in the data sheet I got. 
_But_
I tested several of them in camparison to a Bruel & Kjaer Mic and
found them to be flat from 100 Hz to >20kHz with a max. deviation of
+/-0.5 dB !
From 100 Hz down to 20 Hz there was a decraese of about 3 dB, which
could be corrected by means of a simple filter.

The price is 50 DM, which is $34.

If   your intend is to do conventional sound pressure level
measurements I recommend them without any doubt. But if you are going
to do something like a Fourier analysis, the response to impulses will
be relevant, which is something I did not test.

Output voltage:                    10 mV/Pa +/- 2.5 dB
Output Impedance:            app. 1.5 kOhms at a supply voltage of 5 V
Power consumption:         app. 0.15 mA at a supply voltage of 5 V
Operating temp. range:    -10 to +50 degrees Celsius
Equivalent noise:               app. 29 dB

Diameter:                              4.75 Millimeters (0.187 inches)
Length without wires:         4.20 Millimeters (0.165 inches)

To preserve the good high frequeny response, you should mount them at
the top of a grounded metal tube which is 4 or more inches long (The
longer the better). The diameter of the tube should not exceed 5 to 6
Millimeters.

Such tubes fit well into the cable outlet of an XLR Connector.
Because  the capsule is a three pin type (One for the supply voltage,
one for the output and one for the GND pin) you can not use a BNC
connector at the microphone itself unless you mount the battery at the
end of the tube. 

I think that because of the low price and high quality of this
microphone it would be worth to send a fax to SENNHEISER in order to
get a list of their international distributors.

Please make sure that you get the KE4-211-2  (Part #172280) capsule,
because the different types look all the same.

In article <cstevens-0109951235590001@cstevens.advtech.uswest.com> cstevens@uswest.com (Clarke Stevens) writes:
>In need some instrumentation microphones and accelerometers for some
>multi-channel (16) DSP tests I am running.  My current choices seem to be
>B&K and HP's DSA brand.  Both of these are quite expensive.  Does anyone
>know of some less expensive options that would meet the following
>criteria?
>
>* Flat frequency response from about 30 Hz to about 8 kHz or better
>* Consistent quality
>* Battery powered power supplies/amplifiers
>* BNC output
>* Reasonable environmental tolerance (i.e. mounted to a vehicle in the hot sun).
>
>Thanks in advance,
>Clarke
>
>-- 
>-------------------
>J. Clarke Stevens
>cstevens@uswest.com

You can try some of the el-cheapo Panasonic modules from Digikey. They
are pretty good for their price. See the ongoing thread on Mitey Mike
in rec.audio.tech.

Shankar