Multimeter and Signal Generator

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

 

[Tim Wescott]

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

 

[M Philbrook]

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

 

[Tim Wescott]

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

 

[M Philbrook]

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

 

[Ron M.]

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.