Formula of PT filter in MFD-TAP13-PT-A

[Elka]

Hello,

I am a coffee roaster from Poland who bought a machine for roasting cofee
driven by Moeller PLC and MFD-TAP13-PT-A.
My temperature readings were heavily smoothed by PT1 filter. We switched
the filter off   but would like to know the exact formula of the filter which was damaging our data in the past.

Any help will be welcome.

[radar17892]

Hi Elka,
For help, we need the PLC type (800, EC4P, ...).

PT1 filter FT in easy800 PLC:

Y(t) = [Ta/Tg] x [Kpx (x(t) - Y(t-1))]

regards Thomas

[Elka]

Thank you so much! Nobody has been able to answear this question so far, even then I had asked Moeller in Germany and in Poland and send my PLC documentation to Moeller offices.

My PLC is Easy M800 and MFD Titan.
We had 2 temperatures readings, corrisponding to BT (bean temperature)  and ET (environmental temperature).


When BT was not in oscillations mode due to burner way of working (1 minute ON, 1 minute OFF) a delay in BT reading was as big as 60 s. In oscillation mode strong smoothment was observed (the amplitude of BT oscillations was cut by 2/3) . When the burner was OFF BT/ET temperatures seemed to rise and when it was OFF they seemed to decrease.

Near  local extrema the delay seemed to rise and decrease..What is K in your formula? What is Ta and Tg?
Thank you for your explanations once more..

[Elka]

We have found such an item:

ftp://ftp.moeller.net/DOCUMENTATION/AWB_MANUALS/h1365g.pdf

and read on the page 33 about PT1 smoothing filter but we still don't understand what is Kpx?

we know that: (t) is probably the real temperature registered by PT100. y(t-1) is the display reading just one sample time before. Kpx is any amplification...

Ta-actual time?
Tg delay time

[Elka]

we have found also an information (on Polish Elektroda.pl) tat K=0,38 for an "ideal" low pass filter..

[Elka]

In attached file you may  find a comparison beetween real measurment from Pt100 via Phidget 1046 and smoothed "mesurment"  by our ex-PT1 filter.

If we could know the exact formula of our filter it would be GREAT!

[Elka]

Here is the correct file. The previous one seemed to be empty

[Elka]

Everything is described also here:

http://www.home-barista.com/home-roasting/2014-world-coffee-roasting-competition-profiles-t31029-20.html

and you may see plots posted by my husband under nickname "Antonio"

[Elka]

Here is a screen of our PT1 filter:

http://datasheet.octopart.com/MFD-TAP13-PT-A-Moeller-datasheet-5399030.pdf

[radar17892]

Hi,
here is the User Manual for easy800:

Code: [Auswählen]

ftp://ftp.moeller.net/DOCUMENTATION/AWB_MANUALS/MN04902001Z_EN.pdfPlease read page 192-195 to understand the FT function block.

[Elka]

thank you very much :-)
I have got it finally
Goodnight 

[Elka]

I would like to ask if from my pdf file with data (I would like to send also another one representing a full roasting session) is possible to simulate/calculate (?) the exact formula of MY filter? its Tg and Kp. How?

I am a biologist, non an electronic engeener so I cannot do it by myselve..
It would be possible to find my Kp/Tg somewhere in the easy project also?
I have a copy of it.

All

[Elka]

I would like to ask also if this fiter may be described as lower pass filter or inertion filter?

[radar17892]

Hi Elka,
FT is a low-pass filter. Your data table shows it.
It is possible to simulate/calculate FT funktion with EXCEL. If you use Easysoft, you can log and show function values online in software oscilloscope. Here you can see the step response of signals in your program, to optimize the process.

Professional function simu software are SIMULINK, Mathlab ...

I think, Kp (proportional gain factor) shold be 100 (=factor 1)

Here is a screen of our PT1 filter:
http://datasheet.octopart.com/MFD-TAP13-PT-A-Moeller-datasheet-5399030.pdf

MFD-TAP13-PT-A is not a filter, it`s an I/O modul with PT100 sensor inputs

Thomas

[Elka]

Hi Thomas,

my data were already simulated by a Polish engeener and he obtained K=0,38
He thinks a low pass filter does not describe this problem. He made my a spectrum analysisis of signals, but I would like to know the EXACT formula..

When the coffee is roasted and the roasters does not try to keep the temperature stable, data are delayed by 60s..

We switched OFF the filter now..