I've been thinking for a while about building my own test rig. Not a high resolution set up. Just a portable function generator and a meter that will read Vrms and dBu. I'm thinkig multimeter size. I've tried a couple of cheap DIY oscilloscope things from ebay, just for monitoring waveforms while fault finding. But I'd like something more.
I'm starting this thread as an idea. If anyone with more experience wants to step in, be my guest! I've done a bit of analogue design, digital stuff is new to me. I'm currently reading a book about PICs and my ideas are flowing. But I think this "audio multimeter" would be useful to everyone on this forum. It warrants the knowledge of the pros! I'd like to include an ESR measurement feature too...
Anyway.
So I'm thinking a box, with LCD meter. 9V PP3 battery, XLR in and out. Function generator and level meter all controlled by a PIC.
METER:
XLR input
Switchable input impedance (balanced) 100k, 10k, 600ohms
will read Vrms, Vpk, dBu
uses that2252 rms converter and 8 bit ADC built into PIC (see app note an119)
2 ranges:
-100dBu to +20dBu @ 0.5dB resolution (Noise floor & whatever you like)
-30dBu to +30dBu @ 0.25dB resolution (frequency repsonse and headroom testing)
Peak hold/clear switch
FUNCTION GENERATOR:
XLR output
Uses DDS chip of some sort
Sine/Square waveforms and pink noise
Variable frequency/level
Maxiumum output level from 9V battery ~11dBu. Problem?? Other than headroom testing?
How do you meter what the function generator is doing I hear you say? well when you adjust the function gen the LCD meter automatically switches to read the function gen. Clever eh!?
What about USB connectivity!
*Charges battery?
*Automation of frequency sweeps?
*What else??
Am I naive to think this is possible? Why hasn't it been done before??
I'm not fussed if it's accurate. It's just a useful pocket meter to read line level stuff at various frequencies...Who wants one??
I'm starting this thread as an idea. If anyone with more experience wants to step in, be my guest! I've done a bit of analogue design, digital stuff is new to me. I'm currently reading a book about PICs and my ideas are flowing. But I think this "audio multimeter" would be useful to everyone on this forum. It warrants the knowledge of the pros! I'd like to include an ESR measurement feature too...
Anyway.
So I'm thinking a box, with LCD meter. 9V PP3 battery, XLR in and out. Function generator and level meter all controlled by a PIC.
METER:
XLR input
Switchable input impedance (balanced) 100k, 10k, 600ohms
will read Vrms, Vpk, dBu
uses that2252 rms converter and 8 bit ADC built into PIC (see app note an119)
2 ranges:
-100dBu to +20dBu @ 0.5dB resolution (Noise floor & whatever you like)
-30dBu to +30dBu @ 0.25dB resolution (frequency repsonse and headroom testing)
Peak hold/clear switch
FUNCTION GENERATOR:
XLR output
Uses DDS chip of some sort
Sine/Square waveforms and pink noise
Variable frequency/level
Maxiumum output level from 9V battery ~11dBu. Problem?? Other than headroom testing?
How do you meter what the function generator is doing I hear you say? well when you adjust the function gen the LCD meter automatically switches to read the function gen. Clever eh!?
What about USB connectivity!
*Charges battery?
*Automation of frequency sweeps?
*What else??
Am I naive to think this is possible? Why hasn't it been done before??
I'm not fussed if it's accurate. It's just a useful pocket meter to read line level stuff at various frequencies...Who wants one??