Talk:Hysteresis

message: The first sentence uses the terms
*path-dependence
*rate-independent memory
which as a general reader I have no clue what they are.
Can someone who knows the subject write a definition that is more understandable to a general audience?
Federico Grigio, alias Nahraana (talk) 18:20, 20 March 2008 (UTC)
replies: text: I've just looked at a half-dozen definitions - how's this ?  I'm finding it difficult to phrase so that we don't talk about the rate of change with respect to time - it's not a differntiator or a high-pass filter. I thought working in the rubber band in the lead woudl be a good physical model, although I doubt many people ever notice that a rubber band stays longer the first time you stretch it. I'd like to mention the idea of "stickyness" in the lead, too.   --Wtshymanski (talk) 19:13, 22 September 2011 (UTC)
replies: text: I think you were headed in the right direction, Wyshymanski, but in my opinion the whole lead section needed major surgery to eliminate unnecessary terminology and a lot of redundancy. So I operated. RockMagnetist (talk) 23:55, 22 September 2011 (UTC)
replies: text: Mmm, don't care for the results, nor for my last revisions either. "Memory" has absolutely the wrong connotations, especially for a reader sitting in front of a box with mumblety-mumble gigabytes of "memory".   A path is a beaten down trail between the trees, or so may our reader think. What "path" are we talking about? And the lag is not a *time* lag; "lag" and "delay" imply time, and it's not necessarily anything to do with time. --01:51, 23 September 2011 (UTC)

text:  From "Physics of Baseball& Softball" by Rod Cross, through the magic that is Google Books:
 Hysteresis refers to the fact that different graphs of force vs. compression are obtained depending on whether the force is increasing or decreasing. A graph of force vs. compression ... for a metal spring is a straight line, and it is the same regardless of whether the force is increasing or decreasing. A graph of force vs. compression for a baseball...is a curved line and its shape does depend on whether the force is increasing or decreasing."  This is closer to what we need here, but has too much "whether" in it. --Wtshymanski (talk) 02:01, 23 September 2011 (UTC)
replies: text: The problem is, talking about whether some input is increasing or decreasing implies that only the trend matters, when in fact a particular set of extrema is often what determines the output. I think "memory" has exactly the right connotations, because computer memory is based on hysteresis! RockMagnetist (talk) 02:38, 23 September 2011 (UTC)
replies: text:  You can make little BH loops, or bigger BH loops...but they are still loops even for small values of H.  It's not the extrema that make hysteresis,its absolutely the history of the dependent variable - that's what the original, correct, but opaque lead meant by "path dependent". A flip flop is not a good model for hysteresis. The key element is that you don't get a single curve of effect vs. cause but instead varying results depending on the direction of change. --Wtshymanski (talk) 13:26, 23 September 2011 (UTC)
replies: text:  For an example where the trend doesn't matter, see the Stoner–Wohlfarth model, the main model for single-domain magnets (as are used in magnetic tapes, for example): the change in magnetization is reversible except at jumps.  For what I mean by "a particular set of extrema", see the book by Mayergoyz. But we're getting off the topic of the lead section. I think my current revision is correct and a lot simpler than the one that Nahraana was complaining about. RockMagnetist (talk) 15:37, 23 September 2011 (UTC)
thread_title: Basic definition of hysteresis is in hieroglyphs

message: The associated section describes the unloading and loading of weights attached to an "idealized" rubber band. Intuitively, as the rubber band is loaded, its length will extend and, as its length extends, its elasticity will decrease. As the elasticity of the rubber band decreases, the rate at which its length increases with additional loads likewise decreases. One would, therefore, expect, in the aforesaid figure, that the Force-Extension curve of the loading phase to approach a limiting Extension value. As the load or Force exerted on the band increases, the Extension will increase, eventually approaching, but never exceeding that limiting value. The Force-Extension curve should, therefore, eventually inflect upward. This is not depicted in the figure. The unloading phase would occur in an analogous manner. 
The curve should resemble this:
http://www.revisionworld.co.uk/files/strain_33.gif  —Preceding unsigned comment added by Atlasfugged (talk • contribs) 06:05, 10 October 2010 (UTC)
replies: text: I agree. I propose that the figure be replaced so it provides a better graphical description.George Rodney Maruri Game (talk) 18:07, 7 November 2010 (UTC)
thread_title: Consider Revising Or Replacing The Figure For Elastic Hysteresis Of A Rubber Band 

message: The two phenomena are closely related (at least, in the area of electronic circuits). Any amplifying circuit with positive feedback having a loop gain B.A > 1 possesses hysteresis and v.v., any circuit with hysteresis is an amplifying circuit that is comprised by such a positive feedback. IMO it is impossible to separate them (to have a hysteresis without positive feedback and feedback without hysteresis); we can use positive feedback to obtain hysteresis.
A proportional (fully analog) thermostat is an amplifier (comparator) with only a "global" negative feedback (consisting of cascaded heater, an object and a thermo sensor). The comparator of the simpler bistable thermostat has in addition a "local" positive feedback that forces the transition between the two supply rails and creates the needed hysteresis. Another example: op-amp relaxation oscillator. But how does the positive feedback do this magic? How do we obtain hysteresis by applying feedback? How do we create dual-threshold circuits? How do we convert a one-threshold circuit into a two-threshold one?
Dynamic threshold. The first trick is very simple and intuitive - when the input voltage crosses the threshold in some direction the very circuit changes slightly its own threshold to the opposite direction (i.e., it subtracts voltage from the threshold that is equal to adding voltage to the input voltage). So, the output affects the threshold and do not impact on the input voltage. These circuits are implemented with differential amplifier with series positive feedback where the output is connected to the non-inverting input and the input - to the inverting input. In this arrangement, the humble loop forms the needed summing circuit in the figure (the circle with "+" inside). Examples: classic emitter-coupled transistor Schmitt trigger, op-amp inverting Schmitt trigger, etc.
Modified input voltage. The second technique is opposite - when the input voltage crosses the threshold in some direction the circuit changes slightly the very input voltage in the same direction (i.e., it directly adds voltage to the input voltage). In this case, the output affects (helps) the input voltage and do not affect the threshold. These circuits can be implemented by a single-ended amplifier with parallel positive feedback where the output and the input source are connected through resistors to the non-inverting input. Now, the two resistors form the needed summing circuit (the circle with "+" in the figure). Examples: collector-base coupled transistor Schmitt trigger, op-amp non-inverting Schmitt trigger, etc.
From the feedback view, both the techniques above are the same - systems with positive feedback that is out of control. In both the circuit, the output voltage increases the derivative (difference) input voltage of the comparator (not of the whole circuit!) by decreasing the threshold or by increasing the circuit input voltage. The threshold and memory properties are incorporated in one element (two in one:)
Two different static thresholds. In this case, the threshold and memory properties are separated. The two different thresholds are created by separate ordinary open-loop comparators (without hysteresis) that drive an RS trigger (2-input memory cell). Again, there is a positive feedback but now it is concentrated only in the memory cell. Example: 555 timer. Circuit dreamer (talk, contribs, email) 22:25, 12 November 2010 (UTC)
replies: text: Nevertheless I have restored the older text because the statement about positive feedback while removing the thermostat example does not help the reader. The example is unusual in an encyclopedic article, particularly the lead, but it is about the only text on the page which tells a reader what hysteresis actually is. It needs some cleaning which I might get a chance to do later. I agree that positive feedback is involved, although I haven't thought about the issue enough lately to form an opinion on whether it is an essential component (my guess is "yes, it is", but there may well be a counter example). Regardless of that, positive feedback is a mechanism to implement hysteresis, and not a defining characteristic. Johnuniq (talk) 00:11, 13 November 2010 (UTC)
replies: text: I am very glad to find this discussion here, because I found the article non-sensical.  The only part of the intro that was intelligible was the bit about thermostats -- but a thermostat is the canonical example of a negative feedback loop (the increase in temperature triggers the shut off of the part of the system that increases the temperature.)  I am left with the impression that either someone is badly confused that hysteresis has something to do with positive feedback, or that the role of positive feedback in hysteresis has been inadequately explained. 24.61.41.34 (talk) 04:31, 27 May 2013 (UTC)
thread_title:  About the relation between hysterisis and positive feedback 

message: (the text below is copied from memristor talk)
I do not share Chua's, Ventra's and others' (including memristor) assertions about the (unconditional) existence of hysteresis in memresistive, memcapacitive and meminductive elements (see for example ). Hysteresis is a rate-independent phenomenon like nonlinear resistance. This means that there is no matter if we drive a hysteretic element by slow (DC) or rapidly (AC) changing input quantity; it will show different forward/backward paths (what is the definition of hysteresis) of its IV curve in both the cases. This is not true for a volatile memristor, memcapacitor and meminductor that exhibit "hysteresis" only in the case of slow changing input. If we wiggle the input rapidly, their bizarre ("pinched") hysteresis loop will become a humble straight line (for example, imagine an inert thermistor).
If we assume that volatile "mem" elements possess hysteresis, we should accept that the ordinary ("not mem") capacitors and inductors possess hysteresis as well. For example, if we drive a capacitor with low frequency AC input current, measure the voltage across it as an output and draw its "IV curve", we will probably see a "hysteresis" loop (I am not sure if it will be "pinched"; please, check it:)
It seems only nonvolatile "mem" elements (i.e., true memory elements) should possess hysteresis since their IV curve does not depend on the input rate? Please, discuss this extremely interesting topic; I would like to know if I am right. I have copied this text from memristor talk. Circuit dreamer (talk, contribs, email) 09:48, 10 April 2011 (UTC)
replies: text: I hope you don't mind, but I fixed the memristor links in the above; no thoughts on the issue at the moment. Johnuniq (talk) 09:57, 10 April 2011 (UTC)

text: Hysteresis doesn't have to be rate independent. Consider all the examples involving lag.RockMagnetist (talk) 13:52, 11 April 2011 (UTC)
replies: text: Then the humble capacitor possesses hysteresis? Circuit dreamer (talk, contribs, email) 06:51, 12 April 2011 (UTC)
replies: text: I don't know whether the capacitor's behavior counts as hysteresis. On the one hand, there is a time lag, which is one definition of hysteresis. On the other, there is no net energy loss in a cycle, so there wouldn't be a loop. I don't think merely being humble disqualifies it! But magnetic hysteresis is definitely rate dependent. The slower the time variation, the smaller the loop. RockMagnetist (talk) 13:17, 13 April 2011 (UTC)
replies: text:  There's dielectric losses and polarization in some kinds of capacitors, which would make the voltage across the unit somewhat "path dependent" - and on a crude level, put enough voltage on a real capacitor and it goes "bang" and cannot be reversed to its initial conditions. "Ideal" capacitors, though, wouldn't display hysteresis as I understand it (they're kept in the same lab closet with the frictionless planes, the bottle of ideal gas, and the ideal voltage and current sources). --Wtshymanski (talk) 14:22, 13 April 2011 (UTC)
replies: text: Many real-world capacitors show Dielectric absorption, but that's really another sort of non-ideal behavior separate from hysteresis. As for time lag and energy loss, an ideal opamp with positive feedback has neither. Magnetic hysteresis is an important subset of hysteresis. but we need to avoid definitions that don't apply to other kinds of hysteresis. Guy Macon (talk) 16:53, 13 April 2011 (UTC)
replies: text: Gymacon, you seem to think that I am arguing for a restrictive definition, but it is just the reverse. I am saying that we shouldn't restrict the definition of hysteresis to rate-independent phenomena because that would leave out magnetic hysteresis. RockMagnetist (talk) 19:07, 13 April 2011 (UTC)
thread_title:  Do "mem" elements possess hysteresis? 

message: Hysteresis is a very general phenomena.  It seems that all fields should be treated equally here, not dismissed with "and also's". Certainly, the rest of the article acknowledges this (though the citation's are too sparse), but the introduction should be more universal also.— Preceding unsigned comment added by 146.186.131.40 (talk • contribs) 19:02, 30 March 2012 (UTC)
thread_title:  Generality 

message: The first reference (http://www.ramehart.com/goniometers/contactangle.htm) has been moved to http://www.ramehart.com/contactangle.htm  
I took care of it.
— Preceding unsigned comment added by Marvin W. Hile (talk • contribs) 14:42, 29 October 2012 (UTC)
thread_title:  References 

message: In the section on elastic hysteresis, it says, "In the elastic hysteresis of rubber, the area in the centre of a hysteresis loop is the energy dissipated due to material plasticity."  How can this be caused by plasticity when there is no permanent deformation?  And if this is incorrect, what is the correct name for the property which results in energy dissipation due to internal friction type losses during elastic deformation?
193.52.102.13 (talk) 18:22, 28 January 2013 (UTC)
thread_title:  Elastic Hysteresis (due to plasticity) 

message: I lack the technical expertise to add this topic, but as an amateur I am pretty certain the level of the water table (measured below a nominal ground level datum point) if plotted against the local rainfall will show a  rate-dependent hysteresis effect. The water table falls during dry weather and continues to do so for some hours / days after there is significant rain. Similarly it continues to rise for some time after the rain stops. Would someone like to comment on this observation? I realise that there are other factors in play such as air temperature, evaporation, other sources of water and so on.  --BletchleyPark (talk) 00:10, 2 August 2013 (UTC)
thread_title:  Water table / rainfall hysteresis in Hydrogeology 

message: If a thermostat had positive feedback, the temperature would "run away," overheating more and more, or overcooling more and more.  Thermostats are an example of negative feedback systems.
129.6.57.132 (talk) 17:28, 7 November 2013 (UTC)
replies: text: You're right. Moreover, the hysteresis effect is a property of the feedback, not a result of it. I have removed the offending statement. RockMagnetist (talk) 21:36, 7 November 2013 (UTC)
replies: text: OK, but I think the comment about positive feedback was referring to the process of switching from one state to another, and that is positive feedback. Taking an air conditioner, the overall cycle is negative feedback: rise in room temperature causes cooling to switch on which opposes the initial rise. However, the point about hysteresis is that something has to jam the cooler on by switching it from "off" to "on" with the assurance that it won't swing back to "off" after running for a second. Moreover you don't want the cooler to be switched half-on when the room is a little warm. Johnuniq (talk) 22:41, 7 November 2013 (UTC)
replies: text: If you're right, it would be best to make the point properly in the body of the article (with sources) before adding it back in the lead. RockMagnetist (talk) 23:24, 7 November 2013 (UTC)
thread_title:  Thermostats are negative feedback, not positive 

message: An IP editor has claimed that the diagram in Hysteresis#Elastic hysteresis is incorrect: "The diagram should be a steep gradient followed by less steep and then steep." Does anyone know if that is true? I found one diagram from a publication that looked like the one in this article, but it is just a schematic. A citation would be useful. RockMagnetist (talk) 18:00, 11 April 2014 (UTC)
replies: text: I formally tagged the image itself (:commons:File:Elastic Hysteresis.svg), including several links that support the IP's claim (the IP had also left a note in the image-description there) and a possible origin of the confusion. And I left a note for the uploader of the image at :commons:User talk:Tiger66, but that account appears inactive on all wikis since December 2012. DMacks (talk) 18:33, 11 April 2014 (UTC)
replies: text: Uploader agreed with the problem and uploaded a replacement image that resolves it, so I'm going to un-tag the article. DMacks (talk) 02:12, 14 April 2014 (UTC)
replies: text: That diagram looks like the same one with a different vertical scale. I think the other editor was saying that the curve should have negative curvature at first and then positive curvature - as in this image.  RockMagnetist (talk) 14:52, 14 April 2014 (UTC)
replies: text: If only there were some term to describe a lag between a changed input to a complex system and the resulting output we see! DMacks (talk) 15:32, 14 April 2014 (UTC)
replies: text: It's on the tip of my tongue. RockMagnetist (talk) 16:04, 14 April 2014 (UTC)
thread_title:  Elastic hysteresis diagram 

message: Section 5, Hysteresis in materials, subsection 5.1, Magnetic hysteresis, seems pretty clear to a layman until the end of the second paragraph, reproduced just below:
"...If the magnetic field is now reduced monotonically, M follows a different curve. At zero field strength, the magnetization is offset from the origin by an amount called the remanence. If the H-M relationship is plotted for all strengths of applied magnetic field the result is a hysteresis loop called the main loop. The width of the middle section is twice the coercivity of the material.[16]"
The phrase "...plotted for all strengths of a magnetic field..." probably means for all strengths, both in the original direction and also in the opposite direction.  But this is not clear because the previous sentence stops at "...zero field strength..." which in the diagram is the y-axis. The part of the upper curve to the left of the y-axis is not explicitly explained, either in the text or in the diagram.  Moreover, even less clear is the lower curve in the diagram which is not mentioned at all, much less explained or labelled, which includes its not having any directional arrows.  Wikifan2744 (talk) 20:20, 20 October 2014 (UTC)
thread_title:  Magnetic hysteresis (Section 5.1) 

message: The new lede sentence reads:
*Hysteresis is the time-based dependence of a system's output on current and past inputs. 
I prefer the original lede, but think it should be revised:
*Hysteresis is the dependence of the output of a system not only on its current input, but also on its history of past inputs. 
The editor claims that the original lede violates gramatical conventions, and I am relatively unsophisticated in such matters.  My concern is with readers who have no idea what hysteresis is.  One problem, is that the word "current" might lead the reader to think of electrical current.  I also think a brief definition is not in order here.  Instead, we need more of an explanation.  I reverted the recent edit, and the editor reverted.  The present lede is acceptable, so I will not revert.  But if any editor does not like the lede, please change it. I will continue to watch this page, but will take no action until someone else either edits or adds a comment to this section.  I am not always right in such matters, and I know it.--Guy vandegrift (talk) 16:01, 13 April 2015 (UTC)
replies: text: I think a simple change from "current" to "present" will do it. RockMagnetist(talk) 15:36, 3 September 2015 (UTC)

text: See discussion under  below. —Coconutporkpie (talk) 00:29, 18 September 2016 (UTC)
thread_title:  I don't like the new lede sentence. 

message: The phrase "hysteresis curve" redirects to this page, but the phrase does not exist anywhere in the article. Could someone please add a description, or some kind of correction/explanation if the phrase is somehow discouraged or nonsensical? 72.214.208.2 (talk) 15:26, 23 March 2017 (UTC)
replies: text: The article pretty quickly devolves from the general idea of this topic to specific examples, and only used the term "curve" in relation to each example. I added the more general phrase with a general description to the lede. DMacks (talk) 15:43, 23 March 2017 (UTC)
thread_title:  Hysteresis curve 

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message: Hysteresis is a key concept in the sociology of Pierre Bourdieu.  The concept is necessary for Bourdieu because his key concept of habitus implies a certain delay in adapting to changes in the field. For example, if a factory worker loses their job it may take them some time to be retrained in a new technology. Someone who takes up the piano as a teenager is at a disadvantage by comparison who a person who has had lessons since they were a young child. It may be possible to catch up, but in both examples the person is at a disadvantage in the social field because of their previous experience. Source: Cheryl Hardy, Hysteresis, in Michael Grenfell ed. Pierre Bourdieu: Key Concepts (2008).  — Preceding unsigned comment added by 70.50.141.229 (talk) 03:15, 12 November 2017 (UTC)
thread_title:  Use in sociology 

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thread_title:  External links modified 

message: The text notes that a latching relay may use a solenoid to hold the relay at a position after power is removed, however many latching relays use a magnet to hold the relay's position after power is removed, then power is used to overcome the relay coil's hysteresis and the magnet holding the relay's position. So the ext is a bit off, many latching relays utilize magnets, not solenoids. SoftwareThing (talk) 17:37, 30 August 2018 (UTC)
thread_title:  Matching Relay and Solenoid 

message: The first sentence in section "Types" ends with a Greek letter. This (exact) letter does not appear anywhere else in the document. It either needs to be altered or removed. I'm not familiar with the physics (or I would fix it myself), but it looks like it should be a capital phi.
GregJ77 (talk) 13:29, 8 May 2019 (UTC)
replies: text: Thanks for pointing this out. It's actually a formatting issue - the inline phi looks different from the display phi. I have tweaked the standalone equation and they are still different, but I hope it's now clear they are the same letter. RockMagnetist(talk) 14:46, 8 May 2019 (UTC)
thread_title:  Minor Errors 

message: The lead defines hysteresis simply as system dependence on history. I'm no expert here, but as I read into the topic it seems that hysteresis usually means something much more specific. Morris (2011) points to "two key aspects of hysteresis that are still regarded as characteristic today: “lagging” and rate-independence" - this makes it a far more specific system property that simple dependence on history. Kyle MoJo (talk) 04:38, 8 April 2020 (UTC)
thread_title:  Overbroad definition 

message: Short article that has nothing that can't be included in Hysteresis if it isn't said there already. That is, unless someone has material to substantially expand Hysteretic model with, excluding material related to a specific model that should really be in the article about that model (see the List of models section). Largoplazo (talk) 21:24, 25 August 2023 (UTC)
replies: text: Merge. Hysteretic model isn't much of an article at all. All the info on that page can be included on the hysteresis page. Cessaune [talk] 05:51, 20 September 2023 (UTC)

text: Merge. This article would be better served as a section within the main hysteresis article unless significantly expanded. rtrb (talk) 18:10, 15 November 2023 (UTC)
thread_title:  Proposed merge of [[Hysteretic model]] into [[Hysteresis]]