Author Topic: The 'newer' EEVBLOG 121GW Multimeter  (Read 7640 times)

0 Members and 1 Guest are viewing this topic.

Offline taydin

  • Frequent Contributor
  • **
  • Posts: 420
  • Country: tr
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #25 on: November 13, 2017, 12:45:36 pm »
The number of digits defines the precision, which is not dependent on the meter accuracy, even though both are usually confused.
The attached image shows the difference way better than I could explain.

This picture makes the concepts clear, but I would replace the word "precision" here with "stability". A stable voltage reference (whose value changes very little) is very valuable, even if it doesn't output the desired voltage level of say, 10.0000V, but instead outputs 6.28938V.
Real programmers use machine code!

My hobby projects http://mekatronik.org/forum
 

Offline DrGeoff

  • Frequent Contributor
  • **
  • Posts: 709
  • Country: au
    • AXT Systems
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #26 on: December 20, 2017, 04:35:07 am »
It just occurred to me that a nice addition that might be possible in firmware in the V setting is a mode for dBV for AC volts.
I have other meters which give me this reading directly as a mode when measuring ACV. Just thought I'd put it out there.

- Geoff
Was it really supposed to do that?
 

Online EEVblog

  • Administrator
  • *****
  • Posts: 29692
  • Country: au
    • EEVblog
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #27 on: December 20, 2017, 06:43:51 am »
It just occurred to me that a nice addition that might be possible in firmware in the V setting is a mode for dBV for AC volts.

LOL, I forgot it actually has this already. Need to add that to the manual.

 
The following users thanked this post: Andrew McNamara

Offline Bud

  • Super Contributor
  • ***
  • Posts: 3468
  • Country: ca
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #28 on: December 20, 2017, 06:51:23 am »
What is the reference impedance you use to calculate dBm ?
Facebook-free life and Rigol-free shack.
 

Offline DrGeoff

  • Frequent Contributor
  • **
  • Posts: 709
  • Country: au
    • AXT Systems
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #29 on: December 20, 2017, 06:58:04 am »
It just occurred to me that a nice addition that might be possible in firmware in the V setting is a mode for dBV for AC volts.
LOL, I forgot it actually has this already. Need to add that to the manual.

Nice one Dave. Thanks!
Was it really supposed to do that?
 

Online EEVblog

  • Administrator
  • *****
  • Posts: 29692
  • Country: au
    • EEVblog
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #30 on: December 20, 2017, 07:04:42 am »
What is the reference impedance you use to calculate dBm ?

I presume standard 600ohm, but I haven't actually tried this as I forgot all about the feature  :-[
 

Offline Bud

  • Super Contributor
  • ***
  • Posts: 3468
  • Country: ca
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #31 on: December 21, 2017, 02:41:15 am »
This may be source of great confusion for people especially RF people, as many assume 50 Ohm reference impedance. As DrGeoff said better use dBV.
Facebook-free life and Rigol-free shack.
 

Online drussell

  • Super Contributor
  • ***
  • Posts: 1100
  • Country: ca
  • Hardcore Geek
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #32 on: December 21, 2017, 05:51:32 am »
This may be source of great confusion for people especially RF people, as many assume 50 Ohm reference impedance. As DrGeoff said better use dBV.

The usual reference impedance on multimeters is for 600 \$\Omega\$ lines.
 

Offline Bud

  • Super Contributor
  • ***
  • Posts: 3468
  • Country: ca
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #33 on: December 21, 2017, 04:23:13 pm »
Using dBV will eliminate all guesses. This is why I asked my question.

Edit: also, it is not terribly useful to have it tied to 600 Ohm. There is a multitude of measurements done with a multimeter with different circuit impedances, you do not want to recalculate every time, and may not need it in terms of power . In terms of voltage will be more useful, and that is dBV.
« Last Edit: December 21, 2017, 04:26:52 pm by Bud »
Facebook-free life and Rigol-free shack.
 

Offline Andrew McNamara

  • Contributor
  • Posts: 28
  • Country: au
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #34 on: December 22, 2017, 01:35:18 am »
Edit: also, it is not terribly useful to have it tied to 600 Ohm. There is a multitude of measurements done with a multimeter with different circuit impedances, you do not want to recalculate every time, and may not need it in terms of power . In terms of voltage will be more useful, and that is dBV.

600 ohms is the customary impedance for audio frequency measurements of dBm. Given the meter is likely out of spec for RF anyway, 50 ohms wouldn't make much sense. Maybe dBv would be preferable, but for AF, dBm is the tradition - maybe the assumed impedance should be configurable?
 

Offline lowimpedance

  • Super Contributor
  • ***
  • Posts: 1060
  • Country: au
  • Watts in an ohm?
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #35 on: December 22, 2017, 02:40:21 am »
The ancient Fluke 8050a has dB measurement and the REF. impedance is configurable, so having that ability on the 121GW would be very useful. Maybe displaying the currently set REF. IMP. briefly when the function is selected.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline imaradiostar

  • Contributor
  • Posts: 11
  • Country: us
Re: The 'newer' EEVBLOG 121GW Multimeter
« Reply #36 on: May 24, 2019, 04:36:15 am »
Sorry for the bump- any further thoughts on this? dBv would be a nice change to this meter. My ancient Fluke 8050a and 8060a can do it, as can my 187.

Not complaining, just asking. The meter is great!

JT
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf