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Time units on PID server diagrams

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Good day

I want to ask for time units on PIDserver diagrams. On normal mode the units looks like a minutes but deviation 10 seconds.

On Auto Tune mode the units is very smalls, and I do not know which is it. 

Thank you in advance 

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  • MVP 2023


Much of my work is HVAC.  Looking at your graph, as an aside I just want to tell you that I don't  use PID in many HVAC situations.  What I have found is that items being controlled are often asked to do far more movement, more often, and as a result wear out far quicker.   I once had quality Belimos go in only 18 monthsish due to constant excessive juggling by the system which had been changed over to PID (at customer's request as they had heard how fantastic it was) and autotuned during routine actuator renewal.  The old ones were fine after many years of service, but replacement was due.  On replacing the newly failing units, the control was changed back to my non-PID and life went back to normal.  (As I knew it would, but I didn't rub it in their faces too much!)

Such large changes in a control/valve/etc always also have detrimental flow-on effects throughout a system, in my example hot water.  Large thermal changes in piping, gas furnace cranking up harder more often but without much stability equalled higher consumption and stresses, etc. The list is endless.  So bear in mind it's not only the controlled thing that is wearing out faster, it's everything in the system.  If I ever see an actuator/valve doing large movements I almost always find it is being controlled by a PID system.

The trick I use with my non-PID methods is reading temps to .01°C and clever algorithms.  Much off the shelf HVAC stuff only reads to 0.1°. 

No doubt many people here will disagree with what I am saying, citing that it needs better tuning, but it is again a case of empirical data and boots on the site floor Vs theoretical benefits.  Tuning only works on conditions it encounters at the time it is being done.   By it's very nature HVAC is not a "production process".

cheers, Aus

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5 hours ago, Ausman said:

No doubt many people here will disagree with what I am saying

You did not speak favorably about sacred cult of PID, I have to react    >.<

Jokes aside, I used modified method from VisiLogic example program "PID motorized valve" to control 3-point and analogue actuators on systems running 24/7 and valve actuators last a long time. I did use relatively simple method before PID and it worked well, just little less stable.

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Good day. Thank you  Ausman and Isakovic

I with name Hvac becouse I work this, but my question is for comparison of charts by time characteristics.

For example I have four charts with different heaters and I need to comparison its.

I am attached the time values for comparison. In this case I do not not abcissa units (time units) - Ts, To, Tr, Tp

Thank you.


P reg p-2 i-0 d-0.jpg

P reg p-4 i-0 d-0.jpg

PD reg p-4 i-0 d-100.jpg

PI reg p-2 i-2 d-0.jpg

PI reg p-4 i-8 d-0.jpg


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Sorry for derailing topic.

I tried playing with it. When monitoring 1 unit is 1 minute and 2-3 seconds. When running autotune 1 unit is about 30ms. It doesn't seem consistent, it is the same if you change sample time. Maybe it depends on communication with controller.

If you need time values to analyze your system I suggest calculating it manually by dividing your total online time with displayed units under the graph. Maybe someone who knows better can chime in, but I don't see any more settings for time axis.

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Thank you for your  reply.

Your topic is not - derailing topic.  I make standard and cheap automaton systems, my clients want cheap solutions.

I see like same you. The normal mode is 1 minute and 4seconds. In auto tune I do not calculate. But I think the method is from time duration devided the sum ofabcissa units.Is this correct?



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10 hours ago, HVAC said:

But I think the method is from time duration devided the sum ofabcissa units.Is this correct?

Yes, that's how I would do it. Wait for graph to reach some round number, take screenshot, then read "duration" time from "Online" box and calculate ratio.

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  • MVP 2023

Glad your issue is solved.  Thanks Isak.

I did say "as an aside" so that was my excuse for going off-topic.  But I still think it relevant if your main aim is

On 5/14/2021 at 3:48 AM, HVAC said:

my clients want cheap solutions

Cheap solutions should also mean cheap in the long run!  That was the issue I (the client) was faced with, much larger long term maintenance bills.  In some ways good for me, but not my nature and very wasteful of resources.  Keep in mind what I said about HVAC is not like a normal production process.  However, each to their own methods.

Cheers, Aus

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