Author Topic: What does it means: Absolute Resistor Value Temperature Drift  (Read 3640 times)

0 Members and 1 Guest are viewing this topic.

Offline nourTopic starter

  • Frequent Contributor
  • **
  • Posts: 271
  • Country: sa
  • calm down, it is just a smoked oPamP!
I am aware of the meaning of temperature drift but I don't think I understand the meaning of "Absolute"?

Also, I don't see this term in other devices like op amps or voltage reference! which is confusing, is it something related to resistors only?
if what I have wrote doesn't make sense for you or you think there is something wrong, please correct me, I am still beginner and what I know probably less than what you know
 

Offline pitagoras

  • Regular Contributor
  • *
  • Posts: 116
  • Country: fr
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #1 on: June 05, 2017, 04:27:24 pm »
I would say it is how many ohms a resistor changes for every degree of change
 

Offline Muxr

  • Super Contributor
  • ***
  • Posts: 1369
  • Country: us
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #2 on: June 05, 2017, 04:52:04 pm »
Absolute is opposite of Relative.
Quote
Some circuits require constant ratios among a number of resistors but not the absolute stability
of each individual resistor. For example, the accuracy of an operational amplifier depends on
the accuracy and stability of the ratios of the input, feedback, and bias resistors; if all resistors
move together to maintain the constant ratio, the op amp accuracy remains constant. The
resistor manufacturer may test resistors and select a set with a good TCR match to achieve the
Facts a Glance
From: Vishay Foil Resistors
July, 2013
FACTS #121
- 4 -
required ratio stability over a defined temperature range. But this neglects the power-induced
divergence of resistance values through service life.


http://www.vishaypg.com/docs/63517/FACTS-121.pdf

So absolute is as it says the absolute drift of a resistor, not the relative drift between resistors of the same type (which might be lower if you expect resistors of the same composition to have similar drifts). At least that's how I am parsing it.
« Last Edit: June 05, 2017, 04:54:59 pm by Muxr »
 

Offline nourTopic starter

  • Frequent Contributor
  • **
  • Posts: 271
  • Country: sa
  • calm down, it is just a smoked oPamP!
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #3 on: June 05, 2017, 06:24:43 pm »
I would say it is how many ohms a resistor changes for every degree of change

It would still be the same if we omit the word absolute refer to any opamp datasheet and look at Vos drift, there is no absolute there!

Absolute is opposite of Relative.
Quote
Some circuits require constant ratios among a number of resistors but not the absolute stability
of each individual resistor. For example, the accuracy of an operational amplifier depends on
the accuracy and stability of the ratios of the input, feedback, and bias resistors; if all resistors
move together to maintain the constant ratio, the op amp accuracy remains constant. The
resistor manufacturer may test resistors and select a set with a good TCR match to achieve the
Facts a Glance
From: Vishay Foil Resistors
July, 2013
FACTS #121
- 4 -
required ratio stability over a defined temperature range. But this neglects the power-induced
divergence of resistance values through service life.


http://www.vishaypg.com/docs/63517/FACTS-121.pdf

So absolute is as it says the absolute drift of a resistor, not the relative drift between resistors of the same type (which might be lower if you expect resistors of the same composition to have similar drifts). At least that's how I am parsing it.

So basically, the "Absolute" term means the drift relative to the resistor as an entity not relative to other resistors? well, why don't we see the same term in other devices datasheets? and why not just say drift and everyone will know we are talking about the resistor itself and say relative drift if we are talking about resistor among others?
if what I have wrote doesn't make sense for you or you think there is something wrong, please correct me, I am still beginner and what I know probably less than what you know
 

Offline Conrad Hoffman

  • Super Contributor
  • ***
  • Posts: 1928
  • Country: us
    • The Messy Basement
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #4 on: June 05, 2017, 06:50:14 pm »
Long ago you'd see the term "absolute ohms" as opposed to "international ohms". I wonder if it's a carryover of some sort.
 

Offline pitagoras

  • Regular Contributor
  • *
  • Posts: 116
  • Country: fr
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #5 on: June 05, 2017, 07:11:43 pm »
I would say it is how many ohms a resistor changes for every degree of change

It would still be the same if we omit the word absolute refer to any opamp datasheet and look at Vos drift, there is no absolute there!


It would help if you show us the context.
Absolute might indicate that it is expressed in ohms rather than ppm (i.e. relative to the resistor value).
 

Offline nourTopic starter

  • Frequent Contributor
  • **
  • Posts: 271
  • Country: sa
  • calm down, it is just a smoked oPamP!
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #6 on: June 05, 2017, 07:16:58 pm »
It would help if you show us the context.
Absolute might indicate that it is expressed in ohms rather than ppm (i.e. relative to the resistor value).

from LT5400 Datasheet:
Quote
8ppm/°C Absolute Resistor Value Temperature Drift
LT5400
It is indicated in ppm not in ohms!
Which lead me to ask, which is important? the relative or the absolute drift?
if what I have wrote doesn't make sense for you or you think there is something wrong, please correct me, I am still beginner and what I know probably less than what you know
 

Offline pitagoras

  • Regular Contributor
  • *
  • Posts: 116
  • Country: fr
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #7 on: June 05, 2017, 07:57:01 pm »
It would help if you show us the context.
Absolute might indicate that it is expressed in ohms rather than ppm (i.e. relative to the resistor value).

from LT5400 Datasheet:
Quote
8ppm/°C Absolute Resistor Value Temperature Drift
LT5400
It is indicated in ppm not in ohms!
Which lead me to ask, which is important? the relative or the absolute drift?
What I understand in this case is that the measured value of each resistor can drift at 8ppm/C, but the ratio of the resistors are within 0.2ppm/C. I.e they drift "together".
 

Offline Muxr

  • Super Contributor
  • ***
  • Posts: 1369
  • Country: us
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #8 on: June 05, 2017, 08:43:15 pm »
LT5400 is a quad matched resistor network, so that's why they feel the need to call it absolute to let you know that they mean absolute not compared to the other resistors in the network. There is no need to call something absolute when talking only about one resistor (as opposed to a matched resistor network).
 

Offline nourTopic starter

  • Frequent Contributor
  • **
  • Posts: 271
  • Country: sa
  • calm down, it is just a smoked oPamP!
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #9 on: June 05, 2017, 10:11:47 pm »
LT5400 is a quad matched resistor network, so that's why they feel the need to call it absolute to let you know that they mean absolute not compared to the other resistors in the network. There is no need to call something absolute when talking only about one resistor (as opposed to a matched resistor network).
In Vishay  datasheet VHP100
They have mentioned this

Absolute resistance  change  (window):
VHP100 < 60  ppm  (- 55 °C to  +  125 °C)
VHP101 < 10  ppm  (+  15  °C  to + 45 °C)

What is the meaning of "absolute" in this datasheet? There is no mention for a resistors array(which is obvious!) to have a need to say absolute! And what does window means?

They have mentioned also it is zero TCR in the title !!!! Why if they later said 10 ppm
« Last Edit: June 05, 2017, 10:14:36 pm by nour »
if what I have wrote doesn't make sense for you or you think there is something wrong, please correct me, I am still beginner and what I know probably less than what you know
 

Offline pitagoras

  • Regular Contributor
  • *
  • Posts: 116
  • Country: fr
Re: What does it means: Absolute Resistor Value Temperature Drift
« Reply #10 on: June 06, 2017, 06:33:49 pm »
LT5400 is a quad matched resistor network, so that's why they feel the need to call it absolute to let you know that they mean absolute not compared to the other resistors in the network. There is no need to call something absolute when talking only about one resistor (as opposed to a matched resistor network).
In Vishay  datasheet VHP100
They have mentioned this

Absolute resistance  change  (window):
VHP100 < 60  ppm  (- 55 °C to  +  125 °C)
VHP101 < 10  ppm  (+  15  °C  to + 45 °C)

What is the meaning of "absolute" in this datasheet? There is no mention for a resistors array(which is obvious!) to have a need to say absolute! And what does window means?

They have mentioned also it is zero TCR in the title !!!! Why if they later said 10 ppm
It is explained in the data sheet. The tcr in ppm/C is nearly zero, so instead of that they define window as the maximum variability in the whole range of operating temperature (which is 60ppm)
 
The following users thanked this post: nour


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf