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Re: Resolution, accuracy, error and digital displays

 

¿ªÔÆÌåÓý

Hi Mike,
Couldn't? agree more.

Before you take in account the measurement accuracy,
No mater how many digits there are, the least significant digit is subject to +/- 1 rounding, so is to be ignored.

We had apprentices bringing in their latest purchase 4 1/2 digit DVM's and the first thing we do is point out in 99.999% of cases that accuracy is at best unnecessary / and misleading.
60 years ago we made do without needing that accuracy.
When trying to align something for a peak or minimum, Auto ranging & flickering last digits are a PITA.
Use an analogue meter, alternately it's the reason why better DVM's have the bargraph function to see trends.

*MOST* voltages quoted in manufactures service manuals have a tolerance of at least 5% (10% is not unusual) 10v =? anything in the range 9.5 --> 10.5v (9 -->11v) is allowable.
Does the fact I read 10.501v mean I should look for a fault, while 10.5v is OK??
All but the very cheapest DVM's suffice, and are expendable when the apprentice over current or inadvertently leave the meter on resistance range while they put the prods on the mains line in strip.


It reminds me of a saying. A man with a clock knows the time, a man with two clocks in probability doesn't.? :-[

Alan



On 05/11/2018 14:23, Michael Maiorana wrote:

I was looking over the latest QST magazine and I had a thought that I wanted to discuss with the group. On the cover was an interesting "dummy load" project that used an array of resistors in an oil bath as the load, and an Arduino Nano to display the output power.?

A voice from my past echoed in my head. Dr. Wolfe taught Chemistry at the community college that I attended. He was bright and energetic, but quite strict. I learned a lot from Dr. Wolf, but the one thing that has stuck with me over the years was his insistence on properly expressing values considering the measurement accuracy and significant figures.

The display on the watt meter on the cover of QST shows 4 figures of accuracy. What I wanted to discuss was if it was reasonable to display 4 digits of precision in this particular instance.?

This is certainly not a criticism of the QST project, but simply an opportunity to discuss the topic.

73
Mike M.
KU4QO
Re: Resolution, accuracy, error and digital displays

 

Hi,

This goes into the deep end fast! Those four digits are resolution. Accuracy is a different thing entirely. I haven't looked at the article (I should) so I don't know what the four digits represent. Milliwatts? Megawatts? (probably not) I wonder if four digits of resoulution, even if accurate to 5 digits, is really needed. Maybe the author had a four digit display in the junk box so he put that fourth digit to work. I am a QRP guy and two digits is a great plenty for me for resoulution with three digit accuracy (third digit not displayed). If I am working with low level bits an RF probe and voltmeter or an oscilloscope is more appropriate (to me). The resolution vs accuracy applies to all of our instruments. We should always be aware of that. MiiliHertz? Harumph!

73,

Bill KU8H

On 11/05/2018 09:23 AM, Michael Maiorana wrote:
I was looking over the latest QST magazine and I had a thought that I
wanted to discuss with the group. On the cover was an interesting "dummy
load" project that used an array of resistors in an oil bath as the
load, and an Arduino Nano to display the output power.

A voice from my past echoed in my head. Dr. Wolfe taught Chemistry at
the community college that I attended. He was bright and energetic, but
quite strict. I learned a lot from Dr. Wolf, but the one thing that has
stuck with me over the years was his insistence on properly expressing
values considering the measurement accuracy and significant figures.

The display on the watt meter on the cover of QST shows 4 figures of
accuracy. What I wanted to discuss was if it was reasonable to display 4
digits of precision in this particular instance.

This is certainly not a criticism of the QST project, but simply an
opportunity to discuss the topic.

73
Mike M.
KU4QO
--
bark less - wag more
Resolution, accuracy, error and digital displays

 

I was looking over the latest QST magazine and I had a thought that I wanted to discuss with the group. On the cover was an interesting "dummy load" project that used an array of resistors in an oil bath as the load, and an Arduino Nano to display the output power.?

A voice from my past echoed in my head. Dr. Wolfe taught Chemistry at the community college that I attended. He was bright and energetic, but quite strict. I learned a lot from Dr. Wolf, but the one thing that has stuck with me over the years was his insistence on properly expressing values considering the measurement accuracy and significant figures.

The display on the watt meter on the cover of QST shows 4 figures of accuracy. What I wanted to discuss was if it was reasonable to display 4 digits of precision in this particular instance.?

This is certainly not a criticism of the QST project, but simply an opportunity to discuss the topic.

73
Mike M.
KU4QO
Good info on Lithium cells

 

If we are going to power test equipment from Lithium based cells we should probably know
more about how they work.? I found this on-line video that is quite informative.


Arv? K7HKL
_._
Re: Test fixtures

 

With the si5351 i strongly suggest to have the 1st if between 100 and 120mhz.
This will give the largest range and fast sweeping as the si5351 can be swept with less register writes.
There is a 8$ ad8307 module on ebay
You may want to amplify the output of the ad8307 with factor 2 to get most out of arduino analog input accuracy
The programmable attanuator is a good suggestion.
?
The crosstalk in the si5351 is a problem. Carefull selection of the 1st frequency is needed, I use 110.7MHz
Erik
Re: Sub 50$ dead bug style VNA goes above 600Mhz

 

Many thanks Erik.
Gilles - F1BFU /Fr

Le?sam. 27 oct. 2018 ¨¤?22:43, <erik@...> a ¨¦crit?:
Just in case you want to build a VNA
Arduino nano, SI5351, 3 SA612, 4 opamps and a pc to do the difficult processing

Contains sw, schematics and measurement examples
Erik



--
Gilles - F1BFU/FR
Re: Test fixtures

 

Here you can find what i build
Sub 50$ dead bug style VNA goes above 600Mhz

 

Just in case you want to build a VNA
Arduino nano, SI5351, 3 SA612, 4 opamps and a pc to do the difficult processing

Contains sw, schematics and measurement examples
Erik
Re: Test fixtures

 

Giles

Fantastic analyzer.? Now others can follow your lead to make their own spectrum
analysis tools.? Thanks for sharing.

Arv
_._


On Sat, Oct 27, 2018 at 2:06 PM F1BFU - Fr - 79 <gilles.f1bfu@...> wrote:
Hi Arv, Sharan, Erik and all

I share with you the design of my future spectrum analyzer based on the Specan.

I liked the construction of erikkaashoek.

73 QRO
Gilles - F1BFU Fr


--
Gilles - F1BFU/FR
Re: Test fixtures

 

Hi Arv, Sharan, Erik and all

I share with you the design of my future spectrum analyzer based on the Specan.

I liked the construction of erikkaashoek.

73 QRO
Gilles - F1BFU Fr


--
Gilles - F1BFU/FR

Spectrum Analyser.pdf
Spectrum Analyser.pdf

Re: Signal Quality Meter

 

has anyone every used or built the kit?Signal Quality Meter sold by "midnight design solutions"?? If so what are your thought about using it to find harmonics? ?

thanks
john kg9dk
Re: function generator

 

Cheers Arv.

I had a look at that one, very interesting.
Re: function generator

 

Terry

Good point.? But I probably need to be careful how I comment it as well.?
Many of the scam sites just cannot resist adding a one-line comment to
act as bait.?

Inexpensive Arduino Based Waverform Generator from Instructables:

That should work.? Thanks Terry.

Arv
_._


On Sun, Oct 21, 2018 at 5:26 PM Terry VK5TM <vk5tm@...> wrote:
Arv, can I respectfully suggest that the posting of just a link and no accompanying text in the group be a no no.

It is a commonly used ploy of scammers and other criminal types to trap people into their various ploys.

I for one never click on links in emails or posts like this.

Terry VK5TM

Re: function generator

 

Arv, can I respectfully suggest that the posting of just a link and no accompanying text in the group be a no no.

It is a commonly used ploy of scammers and other criminal types to trap people into their various ploys.

I for one never click on links in emails or posts like this.

Terry VK5TM
function generator

 

Re: another SNA design

 



One of several blog posts about the SNAjR. and its accessories. Also links to gerber files and sketch.


DuWayne


--
DuWayne,? KV4QB
Re: another SNA design

 

We had 30 built at 2 weekend buildathon. 14 months in the making.

image.png

73 Ken

On Sun, Oct 14, 2018 at 8:21 PM Arv Evans <arvid.evans@...> wrote:
Looks good.? Many seem to be finding that a simple SNA is not all that complex.?
_._


On Sun, Oct 14, 2018 at 6:18 PM Ken <chase8043@...> wrote:
How about this SNA? Designed and bulit by Peel Amateur Radio Club. It's the PARC SNA and won 1st place at FDIM club night.



73

Ken VA3ABN

On Sun, Oct 14, 2018 at 7:48 PM Arv Evans <arvid.evans@...> wrote:

_._
Re: another SNA design

 

Looks good.? Many seem to be finding that a simple SNA is not all that complex.?
_._


On Sun, Oct 14, 2018 at 6:18 PM Ken <chase8043@...> wrote:
How about this SNA? Designed and bulit by Peel Amateur Radio Club. It's the PARC SNA and won 1st place at FDIM club night.



73

Ken VA3ABN

On Sun, Oct 14, 2018 at 7:48 PM Arv Evans <arvid.evans@...> wrote:

_._
Re: another SNA design

 

How about this SNA? Designed and bulit by Peel Amateur Radio Club. It's the PARC SNA and won 1st place at FDIM club night.



73

Ken VA3ABN


On Sun, Oct 14, 2018 at 7:48 PM Arv Evans <arvid.evans@...> wrote:

_._
another SNA design

 


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