5/12/2014 11:16 AM  
Posts: 5 Rating: (0) 
Dear all, Siwarex CS 7MH4 9100AA01 Calibrating a Tank on 3 loadcells, each 20000kg max. weight capacity (2mV/V) Calibrating the tank with siwatool CS version 2.0.11 We did the calibration with the Theoretical calibration option. On the DR3 tabpage we filled in: Sum of nominal loads: 30000 (it should have been 3x 20000 = 60000, but the siwatool can handle only a max value of 32767) and in the PLC prog we multiply it with 2. We have 3 calibration sheets and entered the values in de Loading cell 1  3 as zero offset and the Characteristic values, We want to have 0 digits of decimalpointand a max of 25000kg as weighing range. fyi: Loadcell1: 0,01 2,0009;loadcel2: 0,02  2,0000; loadcel3: 0,01  1,9000. We pressed the "Calculate adj. Digits" and we got values: Average zero offset: 0,013333; weighted av. variables: 1,99669; adjustment zero 5461; Adjustment Digits1: 59172. we pressed "Accept calculation", pressed "accept" and no errors so far! We pressed send after we pressed "load factory settings" first. No errors, the weight changed from 5,65kg to 5476kg. The manual says "After sending th DR3, the command "Characteristic curve shift (15)" has to be executed when the scale is empty". This is what we did, but then we got this ERROR: "adjustment weight is too low or error adjustment digits" The Tank is empty and weighs about 5500kg when it is empty. Can You help me with this problem, i mean 5% of 25000 is 1250kg, while the adjustment weight is: (automaticaly entered) 30000. So what is it i am doing wrong? Thanks! 
5/14/2014 12:03 PM  
Joined: 1/4/2007 Last visit: 9/22/2023 Posts: 1059 Rating: (157)

Hello GerritPeet, If you want to do a Theoretical calibration with sum of nominal loads higher than 32767, you have to do the following steps: 1. Divide in half the “Sum of nominal loads” (=60000 / 2=30000) 2. Divide in half for all load cells the “Zero offset in uV/V” for the load cells (e.g. 0.01/2 = 0.005) 3. Divide in half for all load cells the “Characteristic value” for the load cells (e.g. 2.0000/2 = 1.0000) 4. Push the button "Calculate adj. Digits" 5. Push the button "Accept calculation" 6. Push the button “Send” 7. Execute the command “Characteristic curve shift (15)” while the tank is empty Normally, now you can see the weight value “0 kg”. Did you receive now an error message? Best regards Siwarexi 
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5/14/2014 12:34 PM  
Posts: 5 Rating: (0) 
Dear Siwarexi, Thanks so much for your support! I did not know that i should divide the loadcell specs by 2 aswell. You can not find it anywhere in documentation (?). Next week we will go to this plant, where the tanks are, we will try again. But i do think this will do fine. I will let you know if this is the anwser indeed! Thanks again! Br Gerrit 
5/15/2014 7:02 AM  
Joined: 4/11/2011 Last visit: 4/11/2023 Posts: 132 Rating: (7) 
Why divide something? If you set resolution to 10kg then everything must be ok !? For weighing range 25 ton 10 kg resolution is acceptable ( 0,04% of full range). Question. I have experience with nonSiemens weighing instruments. Scale is calibrated. If for some reason i need to shift zero point more than 1% or 3% (some construction is added or removed), then i do only zero calibration and whole curve is shifted. I do not need perform span calibration. Is this the same with Siwarex or not? 
Last edited by: kriipc at: 5/15/2014 7:04 AMI'm just a human. Mistakes are allowed. 

5/15/2014 9:25 AM  
Posts: 5 Rating: (0) 
Hello krijpc, I do not understand the 10kg resolution? please explain. One can only fill in the resolution decimal pionts where 200 kg with 2 digits is 20000 as value. On you last question: I did the same but with the siwarex cs weighing card. But just zero calibration gives me different weigh values then when i do the shift curve calibtration. An exact explanation, i can not give you, since i do not know how the shift curve works exactly. But i do know if the calibration procedure is carried out the way it should be done, it is very accurate!! we have results: 29000kg for a truck load filled, and the truckweighing platform gives us a value of 29004 kg! (truck driver had gone to the Mc. Do...lds ;) 
Last edited by: GerritPeet at: 5/15/2014 9:31 AM 

5/15/2014 11:46 AM  
Joined: 4/11/2011 Last visit: 4/11/2023 Posts: 132 Rating: (7) 
It is the same as you did. You multiply by 2, i propose 10 ( e.g. 540 x 10 = 5400 kg). Just for simplicity.
How many load cells? Most of inaccuracy is related to the mechanics. Tomorrow i am inspecting 60 ton truck scale. Built in 1990. Now it is not possible reach accuracy of 20 kg. By placing weights on corners electronics shows different values (difference more than 40 kg). 
I'm just a human. Mistakes are allowed. 

5/15/2014 12:12 PM  
Posts: 5 Rating: (0) 
We have 3 loadcells under each tank. a 3 point support under the tank is the best way to weight in my opinion. A 60ton truck scale is often equipped with 4 or 6 or 8 loadcells, so all of them must have allmost the same electrical and mechanical characteristics. 
5/19/2014 5:21 PM  
Posts: 5 Rating: (0) 
Hi Siwarexi, OK, i did all the things you told me. Result is NO ERROR! Problem solved sofar! But, in my programm i multiplied the weighing result by 2. So 10kg will be 20kg on the screen. Is it correct that the weight is now just the weight as you see in Siwatool, fi my weight is about 95kg. And when i step on the tank it shows about 95kg. So the multiply should be times 1? Another question: How is it possible that i could calibrate, with no errors, with the same kind of loadcells, a simular tank but only lighter. The last tanks i calibrated are about 6000kg when complete empty and the former tanks are about 4000kg each, complete empty. Let me know, thanks! 
5/29/2014 7:23 AM  
Posts: 63 Rating: (4) 
When the adjustment with adjustment weight fails? 
3/14/2019 8:11 AM  
Joined: 1/1/2017 Last visit: 9/9/2023 Posts: 311 Rating: (10) 
Dear Siwarexi, Thanks for the guidance. That's really helpful Regards OmKris 
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