Walker

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Before you attempt to use the system on regular PID mode, you'll want to calibrate your temp probe and probably do an auto-tuning cycle of the PID parameters so that you have good control of temps.

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CidahMastah

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Thanks for the tips walker. I didn't see anything about clibrating the probe in the manual. I will have to dig in again and look.

Just curious, is the probe calibrating crucial to running a manual mode test?


Here is the auto tune procedure. What is the purpose of the autotuning? Any recc on whether I should use AT 1 or AT 2? I guess I thought that setting the parameters meant I wouldn't ahve to autotune.


The auto-tune can be started in two ways. 1) Set At=2. It will start
automatically after 10 seconds. 2) Set At=1. Then you can start the auto-tune
any time during the normal operation by pressing the A/M key. During auto
tuning, the instrument executes on-off control. After 2-3 times on-off action,
the microprocessor in the instrument will analyze the period, amplitude,
waveform of the oscillation generated by the on-off control, and calculate the
optimal control parameter value. The instrument begins to perform accurate
artificial intelligence control after auto tuning is finished. If you want to exit
from auto tuning mode, press and hold the (A/M) key for about 2 seconds
until the blinking of "At" symbol is stopped in the lower display window.
Generally, you will only need perform auto tuning once. After the auto tuning
is finished. The instrument will set parameter “At” to 3, which will prevent the
(A/M) key from triggering auto-tune. This will prevent an accidental repeat of
the auto-tuning process.

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CidahMastah

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For the Probe callibration:

4.10 Input offset “Pb”
Pb is used to set an input offset to compensate the error produced by the
sensor or input signal itself.
For example, if the controller displays 5 ºC when probe is in ice/water mixture,
setting Pb=-5, will make the controller display 0 ºC.

8.3 Poor Accuracy
Please make sure calibration i s done by immersing the probe in liquid.
Comparing the reference in air is not recommended because response time of
the sensor depends on its mass. Some of our sensors have response time
>10 minutes in the air. When the error is larger than 5 °F, the most common
problem is an improper connection between the thermocouple and the
controller. The thermocouple needs to be connected directly to the controller
unless a thermocouple connector and extension wire is used. Copper wire or
a thermocouple extension wire with the wrong polarity connected on the
thermocouple will cause the reading to drift more than 5 °F.

I.e.

place probe in ice water and see the temp reading. Adjust Pb as needed to get your reading.

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Walker

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If you want your temp readings to be accurate, you will need to calibrate the probe. They usually have some amount of error on them.

For example: my probe reads 1.3*F too high. In ice water, the probe will read 33.3*F and in boiling water it reads 213.3*F.

You can program this error into the PID and it will account for it on displays and during operation. After entering the amount of error offset, my PID now displays 32*F in icewater and 212*F in boiling water.

If you just want to test that you can heat and boil water, then the probe error is somewhat irrelevant, but if you intend to heat to a specific temp, then you'll want to find out what the error is and account for it in the PID programming.

In the online manual for your PID, the parameter is called "Input Offset" and is shown as "Pb" on the PID display when you are cycling through options.

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CidahMastah

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It would be nice to have it reading the right temp so when I heat strike water it can be pretty darn close.

Thanks for the input - I will definitely callibrate the probe - looks very easy to do once I get some ice water in it.

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CidahMastah

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Walker - any personal experience with the auto-tuning? What are the advantages of using it?

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Walker

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I would suggest taking a small cup and packing it full of crushed ice. Fine crush and pack it in the cup. Then just add enough water to make it like that road slush that turns all grey in the winder. Stick the probe in that to calibrate at 32*F.


I have had mixed results, but my PID is a cheap-o Chinese PID. The autotuning can take a while to complete on mine and I ended up manually massaging the auto-tuned parameters afterwards because I didn't like the way the damn thing was behaving (overshooting).

I don't know if Auber's auto-tune algorithms are better or not, but I can't see how they would be worse.

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CidahMastah

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Thanks for the tips on callibration!

I guess as far as PID's go, the auberin one is at least cheap in price, quality is to be assessed Am I correct in assuming that the auto tuning is a sort of optimization, if you will, of performance of the device based on your parameter settings? i.e. it adjusts some of the parameter settings, if it interprets them as less efficient, based what the fuzzy logic thinks will be the most efficient settings?

I guess it shows I am a total newb at this PID thing Asking all these gd questions What can I say,... inquiring minds want to know haha

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during auto-tuning, the PID basically tries to learn about your system. things like
- if I kick on the heat, how long does it take before I see the temp start to increase
- if I turn off the heat, how long does it take before I see the temp STOP increasing
- if I kick on the heat for a short burst, how much effect on the temp does it cause
- if I don't do anything, how fast does the system lose heat
- etc
- etc
- etc

It gathers information about how your system behaves and then uses that to configure some of it's parameters so that it can better handle your system.

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CidahMastah

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So auto tuning is something that I should do during say a strike water heat or something? Or is it something I do prior to actual use. Sounds like the auto tuning has to be done on the substance that you are attempting to heat.

I could see why the auto tuning may cause overshooting if the fuzzy logic doesn't compensate for the heating curve of a liquid. I know the heating curve for water bringing it from say 33F to a boil is supposed to be constant, but my anecdotal experience seems contrary to that. i.e. it seems like the heating of the liquid struggles until it gains a sort of thermal mass, and then it sling shots the temp up a bit faster.

I wonder if the fuzzy logic compensates for this appropriately (probably depends on the quality of the PID).

Then again my anecdotal recollection of time vs. temp increase could be way off I usually am having a home brew when I am taking wort up to a boil!

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