Forums

Multimeter and Signal Generator

Started by Unknown September 30, 2015
Hi, 

I am using the following multimeter 

http://www.repeater-builder.com/radio-shack/22-812/22-812-operating-manual-en.pdf

My questions is that what is its input resistance or impedance of this meter? 


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I am also trying to find the output impedance of the following signal generator, page 12. I do not have Minirator MR2 pro. I have a simple one. 


http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2-Manual.pdf

I tried to measure the output impedance using mutlimeter. I did this with Signal Generator ON and OFF settings. 

Is this the right way to test the output impedance of the Signal Generator?


melissa
On Wed, 30 Sep 2015 15:20:42 -0700, walravenmelissa wrote:

> Hi, > > I am using the following multimeter > > http://www.repeater-builder.com/radio-shack/22-812/22-812-operating-
manual-en.pdf
> > My questions is that what is its input resistance or impedance of this > meter?
They don't say, so you don't know. If the chain of cheap copies stretches back to something industry standard, it's 10M-ohm or so. If not -- you don't know. You may be able to figure this out with a largish capacitor -- if you connect a fairly accurate 10uF ceramic cap to the leads, charge it up with a battery, then disconnect the battery, the voltage should decay exponentially. Plot voltage vs. time on semilog graph paper, and the slope will tell you the time constant. Then use tau = 1/(R*C) to calculate R. Alternately, get your hands on a string of 10 1M-ohm resistors and measure a battery's voltage through the string -- if the string cuts the measured voltage in half, it's a 10M-ohm meter.
> I am also trying to find the output impedance of the following signal > generator, page 12. I do not have Minirator MR2 pro. I have a simple > one. > > > http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2-
Manual.pdf
> > I tried to measure the output impedance using mutlimeter. I did this > with Signal Generator ON and OFF settings. > > Is this the right way to test the output impedance of the Signal > Generator?
No, it is not. Measure the signal generator voltage with no load, then with a resistor across the outputs. A resistor that cuts the voltage by a factor of two should (if the meter is decently built) equal the generator output impedance. It's a good idea to check the output impedance over frequency, as it may vary. It shouldn't, but it's an instrument without specifications. Unless you're living in abject poverty the best way to find out the input impedance of your meter and the output impedance of your signal source is to throw the cheap stuff away and buy something that actually specifies these things and is made by someone who actually builds to specification. I understand that this may be beyond your means, but unless you're doing all the messing around for fun and for free, or you're just barely getting by financially and calibrating your own instruments is part of pulling yourself up by the bootstraps, then you'll probably come out ahead in the long run by spending more money up front and getting decent test equipment. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
In article <5a22d01f-5d17-406c-8b85-fdc8d1a2c13c@googlegroups.com>, 
walravenmelissa@gmail.com says...
> > Hi, > > I am using the following multimeter > > http://www.repeater-builder.com/radio-shack/22-812/22-812-operating-manual-en.pdf > > My questions is that what is its input resistance or impedance of this meter? > > > -------------------------------------------------------------------------------- > > I am also trying to find the output impedance of the following signal generator, page 12. I do not have Minirator MR2 pro. I have a simple one. > > > http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2-Manual.pdf > > I tried to measure the output impedance using mutlimeter. I did this with Signal Generator ON and OFF settings. > > Is this the right way to test the output impedance of the Signal Generator? > > > melissa
The meter has an input Z of 10Mohm, on page 8. As for the signal generator, it's right there on the page you pointed to. 200 Ohms output Z and with a 200 load it's 6 db down. I think this was a lure post, now I'll check my PC for crap attached to those links. Jmaie
On Wed, 30 Sep 2015 19:09:58 -0400, M Philbrook wrote:

> In article <5a22d01f-5d17-406c-8b85-fdc8d1a2c13c@googlegroups.com>, > walravenmelissa@gmail.com says... >> >> Hi, >> >> I am using the following multimeter >> >> http://www.repeater-builder.com/radio-shack/22-812/22-812-operating-
manual-en.pdf
>> >> My questions is that what is its input resistance or impedance of this >> meter? >> >> >>
--------------------------------------------------------------------------------
>> >> I am also trying to find the output impedance of the following signal >> generator, page 12. I do not have Minirator MR2 pro. I have a simple >> one. >> >> >> http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2-
Manual.pdf
>> >> I tried to measure the output impedance using mutlimeter. I did this >> with Signal Generator ON and OFF settings. >> >> Is this the right way to test the output impedance of the Signal >> Generator? >> >> >> melissa > > The meter has an input Z of 10Mohm, on page 8. > > As for the signal generator, it's right there on the page you pointed > to. > 200 Ohms output Z and with a 200 load it's 6 db down. > > I think this was a lure post, now I'll check my PC for crap attached to > those links.
Man, I looked for that and didn't see it. I'm going blind, I guess. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
In article <coWdnaCFjuh27ZHLnZ2dnUVZ5vednZ2d@giganews.com>, 
seemywebsite@myfooter.really says...
> > On Wed, 30 Sep 2015 19:09:58 -0400, M Philbrook wrote: > > > In article <5a22d01f-5d17-406c-8b85-fdc8d1a2c13c@googlegroups.com>, > > walravenmelissa@gmail.com says... > >> > >> Hi, > >> > >> I am using the following multimeter > >> > >> http://www.repeater-builder.com/radio-shack/22-812/22-812-operating- > manual-en.pdf > >> > >> My questions is that what is its input resistance or impedance of this > >> meter? > >> > >> > >> > -------------------------------------------------------------------------------- > >> > >> I am also trying to find the output impedance of the following signal > >> generator, page 12. I do not have Minirator MR2 pro. I have a simple > >> one. > >> > >> > >> http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2- > Manual.pdf > >> > >> I tried to measure the output impedance using mutlimeter. I did this > >> with Signal Generator ON and OFF settings. > >> > >> Is this the right way to test the output impedance of the Signal > >> Generator? > >> > >> > >> melissa > > > > The meter has an input Z of 10Mohm, on page 8. > > > > As for the signal generator, it's right there on the page you pointed > > to. > > 200 Ohms output Z and with a 200 load it's 6 db down. > > > > I think this was a lure post, now I'll check my PC for crap attached to > > those links. > > Man, I looked for that and didn't see it. I'm going blind, I guess.
I tell myself that everytime I take a leak! :) Jamie
On Wednesday, September 30, 2015 at 9:14:11 PM UTC-5, M Philbrook wrote:
> In article <coWdnaCFjuh27ZHLnZ2dnUVZ5vednZ2d@giganews.com>, > seemywebsite@myfooter.really says... > > > > On Wed, 30 Sep 2015 19:09:58 -0400, M Philbrook wrote: > > > > > In article <5a22d01f-5d17-406c-8b85-fdc8d1a2c13c@googlegroups.com>, > > > walravenmelissa@gmail.com says... > > >> > > >> Hi, > > >> > > >> I am using the following multimeter > > >> > > >> http://www.repeater-builder.com/radio-shack/22-812/22-812-operating- > > manual-en.pdf > > >> > > >> My questions is that what is its input resistance or impedance of this > > >> meter? > > >> > > >> > > >> > > -------------------------------------------------------------------------------- > > >> > > >> I am also trying to find the output impedance of the following signal > > >> generator, page 12. I do not have Minirator MR2 pro. I have a simple > > >> one. > > >> > > >> > > >> http://www.nti-audio.com/Portals/0/data/en/Minirator-MR-PRO-MR2- > > Manual.pdf > > >> > > >> I tried to measure the output impedance using mutlimeter. I did this > > >> with Signal Generator ON and OFF settings. > > >> > > >> Is this the right way to test the output impedance of the Signal > > >> Generator? > > >> > > >> > > >> melissa > > > > > > The meter has an input Z of 10Mohm, on page 8. > > > > > > As for the signal generator, it's right there on the page you pointed > > > to. > > > 200 Ohms output Z and with a 200 load it's 6 db down. > > > > > > I think this was a lure post, now I'll check my PC for crap attached to > > > those links. > > > > Man, I looked for that and didn't see it. I'm going blind, I guess. > > I tell myself that everytime I take a leak! :) > > Jamie
Now that's funny as hell.