Scale limits in impedance measurement

miniDSP and AV Nirvana
J

JLM1948

Member
Thread Starter
Joined
Jan 12, 2019
Posts
129
Hi,
I have finally got the time to set up impedance measurement. I intend to make a database of dynamic and ribbon microphone impedance.
I have used a 2kohm series resistor.
I find that the graph only goes to 1000 ohms.
Trying to change it in the "Limits" box apparently doesn't work.
Of course the cursor indicates the correct value, but I'd like to have the full graph.
Is it possible to have the impedance axis logarithmic instead of linear (which I know is a standard but doesn't make much sense IMO?
 
M

Midiman

Registered
Joined
Apr 1, 2024
Posts
7
I have a similar question. I was trying to measure the input impedance of a 1:1+1 audio line level transformer. I can see a curve at the left side and the cursor shows values between 5k and ~ 200 k but the scale of the Y axis only goes to 1000 ohm so I never actually see the curve.
Is there a way to change that or is REW limited to measuring impedances below 1000 ohm. If so, why?

It is a common use case in my audio lab to measure input impedances of different devices.
 
M

Midiman

Registered
Joined
Apr 1, 2024
Posts
7
Select log impedance axis in the graph controls.

I only have [Frequency axis log/linear] in the graph control. That selects log or linear X frequency axis but doesn't affect the Y axis. Am I missing something?
 
B

Bernard

Member
Joined
May 22, 2017
Posts
121
Midiman said:
Select log impedance axis in the graph controls.

I only have [Frequency axis log/linear] in the graph control. That selects log or linear X frequency axis but doesn't affect the Y axis. Am I missing something?
Click to expand...
Perhaps...
Click on the icon << Limits >> to the right of << Freq.axis >>, then click on << Fit Y to data >>.
 

Attachments

  • no scaling.jpg
    no scaling.jpg
    175.8 KB · Views: 8
  • Fit Y to data.jpg
    Fit Y to data.jpg
    212 KB · Views: 8
J

JLM1948

Member
Thread Starter
Joined
Jan 12, 2019
Posts
129
Midiman said:
Select log impedance axis in the graph controls.

I only have [Frequency axis log/linear] in the graph control. That selects log or linear X frequency axis but doesn't affect the Y axis. Am I missing something?
Click to expand...
It's at the bottom of the "Controls" tag.
Please note that measuring an otherwise unconnected transformer shows a much higher impedance than the nominal impedance. A typical 600 ohms transformer will show as a rising graph from about 1kohm at 20Hz to several hundred kilohms at 20kHz.
 
M

Midiman

Registered
Joined
Apr 1, 2024
Posts
7
Bernard said:
Perhaps...
Click on the icon << Limits >> to the right of << Freq.axis >>, then click on << Fit Y to data >>.
Click to expand...
Doesn't work. When measuring Impedance it goes max. 1000 Ohm on the Y axis. Also entering it manually doesn't work. It jumps back to '1000.'
 
M

Midiman

Registered
Joined
Apr 1, 2024
Posts
7
JLM1948 said:
It's at the bottom of the "Controls" tag.
Please note that measuring an otherwise unconnected transformer shows a much higher impedance than the nominal impedance. A typical 600 ohms transformer will show as a rising graph from about 1kohm at 20Hz to several hundred kilohms at 20kHz.
Click to expand...
Aaaaaaaah.... I found it! (It is in the 'Controls' submenu)
Ok.... that seems to work for my purpose.
And sure, I am aware of the impedance behaviour of transformers. Still, it is a kind of 'fingerprint' of the transformer and it might make sense to linearize that impedance with some components. It is about imagining, what a 'driver' will see.
 
You must log in or register to reply here.
miniDSP and AV Nirvana

Popular tags

20th century fox 4k blu-ray 4k uhd 4k ultrahd action adventure animated animation bass blu-ray calibration comedy comics denon dirac dirac live disney dolby atmos drama fantasy hdmi 2.1 home theater horror kaleidescape klipsch lionsgate marantz movies onkyo paramount pioneer rew romance sci-fi scream factory shout factory sony stormaudio subwoofer svs terror thriller uhd ultrahd ultrahd 4k universal value electronics warner warner brothers well go usa
Top Bottom