Multimeter and Signal Generator

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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

Re: Multimeter and Signal Generator
On Wed, 30 Sep 2015 15:20:42 -0700, walravenmelissa wrote:

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manual-en.pdf
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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.

Quoted text here. Click to load it
Manual.pdf

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
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Re: Multimeter and Signal Generator
snipped-for-privacy@gmail.com says...
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 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



Re: Multimeter and Signal Generator
On Wed, 30 Sep 2015 19:09:58 -0400, M Philbrook wrote:

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manual-en.pdf
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Manual.pdf

Man, I looked for that and didn't see it.  I'm going blind, I guess.

--  

Tim Wescott
Wescott Design Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Multimeter and Signal Generator
snipped-for-privacy@myfooter.really says...
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I tell myself that everytime I take a leak! :)

Jamie


Re: Multimeter and Signal Generator
On Wednesday, September 30, 2015 at 9:14:11 PM UTC-5, M Philbrook wrote:
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Now that's funny as hell.

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