Are these multimeters good for audio work? - Page 2

AmpliFire · 22nd February 2012, 06:16 PM

Yes you are fully right, thanks for putting it right. I could just add that often 'x% of full scale' is often quoted by meter manufacturers, which is mainly the fixed inaccuracy as you mention. But it does mean that an inaccuracy of 4mV at 400mV range still stands, even if you measure 20 mV at a given moment.

lloop9 · 23rd February 2012, 12:15 AM

Thank you for all the valued input guys.

If one were to use a handheld DMM for matching mosfets, jfets, etc, what is the minimum digit count to aim for? Cheap units are mostly 2000 counts, I heard someone said that a 10000 is the minimum?

cheers

AmpliFire · 06:50 AM

Well, it depends on how close you want to match them. The hFE option on DMMs is at one given (low) current only, while close matching rather requires comparing BJT/FET over a wide range, and for power devices preferrably under load.

There is a curve tracer design thread by locky_z going here, with an excellent group buy organised by LazyButt here. You can still order.

Or, an alternative device which allows you to connect any case style (even TO-3 and TO-66), is something like this, but it's not a curve tracer.

And measuring an hFE upto 2000 would be very sufficiant....

lloop9 · 23rd February 2012, 06:55 AM

Thks for the headsup on the curve tracer Amplifire. I just going deal on some Meterman DM9B for $25, they shld serve me well until I'm up for something more advance.

cheers

epicyclic · 1st March 2012, 12:14 PM

Unless i missed it no ones mentioned accuracy when measuring AC signal voltages , for the purpose of gain calculation etc . Its been my experience to be wary of the result when measuring any signal voltage whos frequency is below 50Hz or above 3Khz with an ordinary dvm . Cant give any comparisons between different makes however .

23rd February 2012, 06:45 AM	#13
AmpliFire diyAudio Member Join Date: Oct 2011 Location: Tokyo, Japan	Well, it depends on how close you want to match them. The hFE option on DMMs is at one given (low) current only, while close matching rather requires comparing BJT/FET over a wide range, and for power devices preferrably under load. There is a curve tracer design thread by locky_z going here, with an excellent group buy organised by LazyButt here. You can still order. Or, an alternative device which allows you to connect any case style (even TO-3 and TO-66), is something like this, but it's not a curve tracer. And measuring an hFE upto 2000 would be very sufficiant.... Last edited by AmpliFire; 23rd February 2012 at 06:50 AM.

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22nd February 2012, 06:16 PM	#11
AmpliFire diyAudio Member Join Date: Oct 2011 Location: Tokyo, Japan	Yes you are fully right, thanks for putting it right. I could just add that often 'x% of full scale' is often quoted by meter manufacturers, which is mainly the fixed inaccuracy as you mention. But it does mean that an inaccuracy of 4mV at 400mV range still stands, even if you measure 20 mV at a given moment.

23rd February 2012, 12:15 AM	#12
lloop9 diyAudio Member Join Date: Jan 2004	Thank you for all the valued input guys. If one were to use a handheld DMM for matching mosfets, jfets, etc, what is the minimum digit count to aim for? Cheap units are mostly 2000 counts, I heard someone said that a 10000 is the minimum? cheers

23rd February 2012, 06:55 AM	#14
lloop9 diyAudio Member Join Date: Jan 2004	Thks for the headsup on the curve tracer Amplifire. I just going deal on some Meterman DM9B for $25, they shld serve me well until I'm up for something more advance. cheers

1st March 2012, 12:14 PM	#15
epicyclic diyAudio Member Join Date: Jan 2012	Unless i missed it no ones mentioned accuracy when measuring AC signal voltages , for the purpose of gain calculation etc . Its been my experience to be wary of the result when measuring any signal voltage whos frequency is below 50Hz or above 3Khz with an ordinary dvm . Cant give any comparisons between different makes however .