tempeature stability

[becidea]

Dear All,

how to know a temperature value which is table. for example, I set the temperature to 300K, then I am waiting for the value to be around 300K, when it is around 300K, I will say the program measure.

How can I know that it is 300K and stable?

best

[dsasorin]

Hi. Here is my thought.

You will use case structures and loops.

I think that the easier method will be comparing your actual temperature with the mean of the last 100 values, lets say. If it is in range (297K-303K), you start a counter (add 1 to a shift register). If shift register = lets say, 5, then the temperature has stabilized and you can start to measure (record).

It is up to you for the number of samples and limits.

best regards.

[becidea]

Thanks for your answer,

but I actually want to read data and try to know whether it is stable or not. As your idea I can only understand that I reached that value but I cannot know about the stability!!.

Best.

[EvenDeejay]

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@becidea wrote:

Dear All,

how to know a temperature value which is table. for example, I set the temperature to 300K, then I am waiting for the value to be around 300K, when it is around 300K, I will say the program measure.

How can I know that it is 300K and stable?

best

---

Your question is a bit unclear. If you want to know what the temperature is, you have to measure it. You cannot wait till it's 300K and then start the measuring with software, without having some extra hardware in place that tells LabVIEW that the temp is 300K.

Depending on your timing of course, but here is an example:

Take measurement of the temperature every second and check if it's reached 300K. Then do like it's descibed in the other post to find out if the temperature is stable. Then you can do something further etc.
 

[EvenDeejay]

Regarding stability, you have to define it yourself. What is stable? Is it 300K +/- 5% for lets say 1 minute? You have to define the borders first, then create the code that checks your data

[becidea]

As you can see from the picture, there are some points that temperature can be 300K. So I f I tel the software measure at 300K or near 300K, software will measure first one, or, if gradient big enough, second one will be measured. But unfortunately they are not measurements that I need because there is no stability. comments writen above I know already. But the thing is what should I do?

offers pls.

[Danny_Funk]

becidea,

If you are only getting measurements when the temperature is 300K then you need to be able to compare them some how. You could use timestamps as the factor to compare the different measurements.  For example with your chart those first two 300K measurements are a larger time apart than the consecutive stable measurments. Then you will need to come up with a threshold value that decides if an old measurment is too far from the previous one.

Regards,

Danny F

[Jose_LabVIEW]

Becidea,

I have read your issue and comments that others stated.  I too am a bit confused. However, here is a possible answer for you.

Your measurement loop has to be acquiring faster than the temperature producing equipement or sensor.  As someone stated, you have to define what is stable.  Once you measure your temp and it is out of your stable range, then you perform the next step.

I hope I have answered your question.

J

[Jose_LabVIEW]

Becidea,

I think I know now your issue.

Assuming that your resolution is 1 (rare) Farhenheit/Celcius and assuming that once stable the temperature never fluctuates(rare) then you have a Temp_prev and Temp_current.  Temp_prev and Temp_current should be equal to each other after several measurements.

For example.
Meas 1

Temp_prev = 299, temp_current = 300;  // you know here that temp is still rising base on my assumptions above

Meas 2

Temp prev == 301, temp_current = 300; //you know here that temp is still unstable

Meas 3

Temp_prev== 300, temp_current = 300  // you know here that temp is stable however, we will measure several more times to make sure;

Meas 4

Temp_prev = 300,, temp_current=300

Meas 5

Temp_prev = 3--; temp_current=300; //you can choose how many times you measure to make yourself comfortable that the temp is stable.  After 3 or X measurements and Temp_prev= Temp_current, then i would say that temp is stable.  Again this is based on the assumption above.

However realistically, temp does fluctuate and you have to define what stable is.

J

[becidea]

Dear Jose,

yes this is what I ment. Stability of the temperature, or stable temperature is what you mentoned with giving an example. So this is the answer of my wuestion, but still I don't know how to do in Labview.

So I guess no one can help on this issue, I will try to do by myself

best.