measurement

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dr.power

Member

• Dec 21, 2011

• #1

Hi guys,

I want to use an electret mike and a VU meter to measure the level of an audio signal (between 100Hz to 4Khz) and an ultrasonic signal (between 30kHz to 55kHz).
What do you think of using just ONE electret mike and a couple of VU meters and a filter to do so?

Thanks

 

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Nigel Goodwin

Super Moderator

Most Helpful Member

• Dec 21, 2011

• #2

Do you have a microphone that will pickup ultrasonic frequencies as well as audio ones?.

Assuming you do?, then there's no problem at all doing it.

 

D

dr.power

Member

• Dec 21, 2011

• #3

Hi and thanks.

Yes there are some electeret mikes capable of covering the said frequency.

So can you guys help me about the cut-off frequencies and the filter type (active or passive) for this job plz?
I think I need a low pass filter for the audio measuring and a high pass one for the ultrasonic, right?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Dec 21, 2011

• #4

dr.power said:

Hi and thanks.

Yes there are some electeret mikes capable of covering the said frequency.

So can you guys help me about the cut-off frequencies and the filter type (active or passive) for this job plz?
I think I need a low pass filter for the audio measuring and a high pass one for the ultrasonic, right?

Click to expand...

Yes, you need active ones.

There are plenty of sites that have either applications or programmes for designing filters - you can even download one from MicroChip.

 

audioguru

Well-Known Member

Most Helpful Member

• Dec 21, 2011

• #5

I have never heard of an electret mic that has documented output from 30kHz to 55kHz.
Which one did you find and please post or link to its datasheet.

 

D

dr.power

Member

• Dec 21, 2011

• #6

Gurue,

Plz take a look at the below links, at least 2 of them are condenser mikes:

**broken link removed**

**broken link removed**

**broken link removed**


http://www.avisoft.com/usg/microphones.htm

I think that I have seen a 60kHz band width eleteret mike made by Panasonic, But unfortunatelyI can not remember the part number.

 

audioguru

Well-Known Member

Most Helpful Member

• Dec 21, 2011

• #7

Gasp, cough, choke.
Two thousand, eight hundred English Pounds!!

They are condenser mics that are powered from a 48V supply. An electret mic has the 48V built-into the electret material.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Dec 21, 2011

• #8

If you're looking at mikes costing in the thousands, why are you messing about building gear for them?.

What are you trying to do anyway?.

 

D

dr.power

Member

• Dec 21, 2011

• #9

Actually I am using "MCE-2500" electeret capsule mike as there are some reports in the net indicating that the said mike is able to cover 60KHz (the datasheet does not say anything about the ultrasonic spectrum of the said mike though).
I just wanted to tell that there are ELECTERET mikes covering higher frequencies in the market as GURU requested.

 

D

dr.power

Member

• Dec 21, 2011

• #10

Nigel Goodwin said:

What are you trying to do anyway?.

Click to expand...

I am trying to measure the output of a device like this:
**broken link removed**

Ok first for the audio section, can you guys let me know what kind of filters is good?

Thanks

 

audioguru

Well-Known Member

Most Helpful Member

• Dec 21, 2011

• #11

They don't say so but I think the Holosonics Spotlight speakers operate with ultrasonics and a special processor so that a narrow ultrasonic beam aimed at an object or at a person causes interferences that is demodulated when it strikes the object or the person.

Your ultrasonic mic will pickup the processed ultrasonics. If you slow down the playback then the frequencies will be reduced so that you can hear them but I don't think it will sound like slow speech.