WP241 - Q about the calibration we got

Hello rQx,

During the commissioning the parameters of the WP241 has to set correctly, e.g. belt length, calibration weight, … .

Afterwards a calibration has to be executed when the belt is:
1. empty
2. loaded with a calibration weight (or a test chain).

Also the speed detection has to be controlled in the WP241 for a correct shown value.

The belt angle is not important, if the angle is not changing.

Only to change the “Correction factor” is NOT! sufficient.
The totalizer will work, but you will see an incorrect totalizer value when the load or the speed is changing.

But you can control the WP241 module, if the WP241 is working correctly.
Important for a correct totalizer value are the process values from the WP241:
- weight value
- belt speed

Do you have an HMI-panel (or the Siwatool software) to check these parameters?

Best regards

Siwarexi

Hello rQx,

For doing the calibration you have to do two steps:

1. Execute the zero calibration commands (= “Start initial zero calibration (60)” and “Accept initial calibration digits (88)” ) during an empty running belt
2. Execute the span calibration commands (= “Start span calibration with test weight (61)” and “Accept span calibration digits (89)” ) during an empty running belt AND the test weight is hanging on the belt scale

!!! Only to execute the zero calibration commands is NOT! sufficient for a calibration !!!

When the “speed is somewhat correct but not perfectly”, so the totalizer value is also only somewhat correct but not perfectly, because the totalizer value is calculated from the current weight and the current speed!

Therefore check the two parameters with your Siwatool software:
- current weight
- current speed
You can find these two parameters into the DR30.

To check these two parameters, do the following tests, please:
1. Hang several weights on the belt scale and check the parameter “current weight”
2. Run the belt with different speeds and check the parameter “current speed”

Best regards

Siwarexi

Hello rQx,

“Is maybe the reason that they only did the "correction factor" instead of "span calibration" because we have the metal hinge?”

NO!
A calibration is independent of an existing hinge or not existing hinge!

A calibration must be done  - in every case -  by executing the two steps:
1. Execute the zero calibration commands
2. Execute the span calibration commands

!!! If you can’t see the correct weight value, the calibration was done not correctly!!!

A correction factor of 2.3 is quite high.
In my opinion too high for a correct installed belt scale!

The other belt scale with the correction factor of 13.5 makes absolutely no sense.
13.5 is nonsense!
Also there, the weight value and speed has to be checked!

A wrong belt length means that the time for the calibration is not correct.
During the calibration the belt shall rotate exactly for one belt revolution.
If the time is wrong, the shown weight value is not 100% correct.

“With our construction would it be enough to only do the zero calibration, and then the span calibration with test weight.”
YES

“Or do we have to use the correction factor also because we have the metal hinge?”
The correction factor is calculated by the following calculation:
new correction factor = (transported material over the belt) / (totalizer value of the WP241) x (old correction factor)

Do at first a correct calibration.
THIS IS VERY IMPORTANT FOR YOU!
After that, we can take a look to the correction factor.

I recommend you to ask the company:
- why you don’t see the correct weight value when you put a weight on the scale
AND
- why they didn’t do a calibration with a test weight.

Take a look to the document on the internet on the pdf-pages 28 … 31:
https://support.industry.siemens.com/cs/ww/en/view/109474797

“And how important is the "angle of the belt" if the angle is always the same?”
Not important, if the angle is always the same.
Don’t change this parameter.

Best regards

Siwarexi