Wish list : Extending the sound beeper volume of an Multimeter

[Kiriakos-GR]

Extending the sound beeper volume of an Multimeter , and alternative as choice to light up an light source..

I wish ...   But you, the mega brains, will find the solution that I am looking for ..  

In photography we have the called slave flash units , they get activated by the light of the primary flash,
the modern ones use remote sensors.

Well I believe that an sound circuitry with a Mic  ( Mic + preamp ) + an amplifier like 2W output, it could produce an strong beeping sound , good enough to hear in an noisy environment.  

The mic it could be ( I guess )  like the ones that you was hook up in phones , with the suck mound elastic membrane .

The hard part are the amplified sounds to be limited at the frequency of the latched beeper, so to not amplify anything else ...

Alternatively , the same circuit it should had , and a small relay that it will activate an light source like 10 LED's  ...

So,  if the amplified sound of the continuity beeper ( buzzer ) , its not good enough at extremely noisy environments , the light source will do the trick ..

If your idea are good enough ,  it could become usable and help many Industrial technicians .  

      

[blackdog]

Something like this...
Mice amp, bandpass filter(frequentie buzzer of the meter), Rectifier, Schmitt trigger (level control, that is sensitivity), relais/powerfet controling the LED/Powerbuzzer.
Most of the functions can be done with a cheap quad opamp.
I dont have a schematic at hand, build something like that long time ago...
If i have some spare time this week i will draw schematic for you :-)

Bram

[sonicj]

i would probably use a 2.5mm shunted jack. when the 2.5mm phone plug is inserted, signal is routed to external tone circuit. (555 warble, etc.) when plug is removed, meter returns to normal internal piezo operation.

[alm]

i would probably use a 2.5mm shunted jack. when the 2.5mm phone plug is inserted, signal is routed to external tone circuit. (555 warble, etc.) when plug is removed, meter returns to normal internal piezo operation.

I would be really careful with something like this. The meter is designed to be completely isolated, hence the plastic case and instructions not to use it with battery cover removed. The jack would be directly connected to the common test lead, so insulation rated for 1000V CAT III/600V CAT IV would be required. Why do you think most of these meters use IR for communication?

[Zero999]

Yes, the beeper needs to be coupled via a transformer or an opto-coupler.

[saturation]

I'm not sure I would want anything to cut a hole in the casing of the Fluke 87V.  If you need to amplify sound of the piezo and add lights to it I would simply attach adevice to the Fluke so it amplified any sound it made, and flashed the lights you mention.  There should be no electrical connection between the devices.  

If you want the sound of the Fluke beep alone to be amplified, you can add a pass filter for the specific frequency, but if you make the box connection sufficiently close and stuff it with insulation except for where the mic touches the Fluke, it wouldn't be necessary.

Before you even build this, check if the piezo element inside the Fluke is actually working properly; just put another one is parallel, and if its louder, then maybe the OEm one is defective.  Piezo elements are like capacitors, and 2 in parallel would be like addiing capacitance, so if one dominated, the other has too high an impedance.  What should happen if they are ~ equal, is the sound should be reduced somewhat.

For occasional use, get a an FM mic bug kit, about $10.  



Put it in a box so the mic is above the piezo element.  Use an FM radio to play back the beep.  Now you have unlimited volume, wide distribution, your Fluke is not modified, and the unit should be electrically safe to use.

For flashing LED, put a flashing LED parallel to the mic amp transistor on the PCB of this, as in this schematic.  It should momentarily flash whenever the mic transmits any sound.




Or for permanent dedicated use, get a pocket amp like this and add a microphone to the line input:

http://www.radioshack.com/product/index.jsp?productId=2104056

Then add a speaker or a piezo crystal in lieu of the headset output.

Build the LED circuit above to make the flashing lights as sound occurs.

[blackdog]

OK
1e part of the Buzzer-Amp

OP2 and 3 = Bandpass filter 2 - 4Khz to filter the noise
OP3 = power splitter
OP4 = comparator (need some extra disign  )

Tomorrow more afther some sleep...

www.bramcam.nl/Buzzer-Amp.JPG

Bram

[Zero999]

I think a simpler and more accurate approach is to use the NE567 or a CD4046 as a tone decoder, rather than a band pass filter. You need to be sure of the exact frequency of the beeper so connect a mic and amplifier to a frequency counter to measure the frequency.

[Nermash]

I would propose hardware hacking and installation of small low power transmitter, ZigBee protocol or simillar. Then you place one big fat horn speaker on the factory floor connected with rx, and if you miss the continuity buzzer your coworkers will certainly not fail to notice it

[blackdog]

Kiriakos

Wy do yo want to use your Multimeter for a continuity check.
Maybe just a small box with a speaker and some LEDS, and 2 testwires.

Or is it you want to know if a max of min. is reached on the Multimeter?

Bram

[Kiriakos-GR]

The continuity test , works by two ways ...

1)  You have your DMM at hand , and in this case any test are easy .

2) You have your DMM  hooked with crocks on the cables that you need to be active,
and you are 5 meters away at the nearest cross box ,  trying to locate the cables by sorting just the copper ends .    ( telephone cables are the trickiest part ... they look good ... but only under voltage (load ) you know if they work right )


Basically the extended usability will help the most , when some ones works alone.

To just to give you an picture,  the dimension of the one,  of the five buildings that I work at ,
are 35 meters wide - 120 meters long !!  

(multiply those number by 3 = US Foot )  

[MrPlacid]

Kiriakos-GR, if all you need is a continuity check, why don't you try hacking an alarm. I have done that at the store I worked in. Everytime I needed assistance, I had to yell at the top of my lungs to call them and they still couldn't hear me. I went to fry's electronic and got some cheap alarm for around $12. They were three in a pack, I took out the foot switch one which uses a 9 volt battery. I put everything in an altoid box. The whole thing is really small and compact. It doesn't have a light, but if it works, you probably won't need it. Or you could calculate the voltage consumption of the LEDs and add it in series with the battery, and up the voltage source.

If you are checking telephone wires, you could just hook up a 9v battery to the end of the wires, then run to the other end and check for voltage with your meter. The 9v battery will act like a simple signal generator.

Leave your precious meter too far away and someone is gonna run off with it while you're sorting your cables on the other end.