11/17/2020 11:30 AM  
Joined: 5/27/2020 Last visit: 4/23/2024 Posts: 5 Rating: (0) 
Hello guys,i am newbie in logo programming so any help from you will be very helpful. I want to create a project similar to this.I have a tank which shape is cone at the bottom and cylinder above the cone.The main idea is that i want to measure pressure and with some calculations convert to Kg and show it to logo screen. To achieve this i have a pressure sensor which is 420mA ( 50 mbar to 1000 mbar ) I have the logo 12/24 rce and the analog extension which has two analog inputs. My tank dimensions are these: Height of cylinder : 2,05 m Diameter of cylinder : 2,00 m Height of cone : 0,975 m Diameter of the cone at the bottom : 0,285 m The pressure sensor is installed at the bottom of the cone. First of all i would like some help to make the scale for the pressure sensor in the program.(which blocks to use and the parameterization of the gain and offset to achieve this) The scenario of the program will be the following.There are two cases.Case 1 measure pressure in the region of the cone and with the appropriate calculations this value will be converted to Kg and showed to logo screen. Case 2 measure pressure in the region of the cylinder and with the appropriate calculations this value will be converted to Kg and showed to logo screen. To sum up i want to be sure that the value of the Kg will be precise in the Case 1 and Case 2. Any help or program,if its possible, will be very helpful.Thank you!  
Last edited by: Jen_Moderator at: 11/17/2020 13:46:18New subject after splitting 

11/17/2020 12:49 PM  
Joined: 2/22/2008 Last visit: 5/10/2024 Posts: 2698 Rating: (206) 
You have a total height of ~3m, this will force a max. hydrostatic pressure of ~0.3bar. When you take a sensor up to 1bar, you will loose 70% of accuracy with the analog input of the Logo controller. This makes no sense, if you want to have precise calculations. First step if possible, use an other pressure sensor appropriate to your height. To help you generally with the scaling, connect your analog input to an analog amplifier, change parameter of amplifier as follows. In case of 420mA select this sensor, then change the range on the left side, not gain and offset. If in your case the sensor has 50 up to 1000mBar, then type in 50 as minimum and +1000 as maximum. Gain and offset is calculated by Logosoft. If you get a message, that gain and offset cannot be calculated correct, then it is possible to use 2 amplifiers or an additional arithmetic block. The help for calculating the cylinder and cone is the next step later. Check first your desired sensor to avoid double works. Regards, Scorp P.S. I don't understand your description of both cases. You only need 1 sensor, this is normally at the bottom, which is the lowest position of the cone. With the sensor the height is calculated independent of the diameter. The kg is calculated with the calculated height and the density of your liquid using two formulas for the different areas. 
Last edited by: Scorp at: 11/17/2020 13:14:05Last edited by: Scorp at: 11/17/2020 13:15:57 

11/17/2020 2:13 PM  
Joined: 5/27/2020 Last visit: 4/23/2024 Posts: 5 Rating: (0) 
First of all thank thank you for the fast response Unfortunately i cant change my sensor because it is already welded at the bottom of the tank. For the analog scale i have connected an analog input to an analog amplifier SF01(characteristics 420mA sensor,minimum 0,maximum 1000).Then i have connected an analog contact SF01 to another analog amplifier SF02 (characteristics no sensor,minimum 50,maximum 1000).You can see the picture that is in the post.I think that the analog scale is ok.Correct me if i am wrong. P.S With the two cases 1,2 i mean that i want to be sure that i will measure the correct number of Kg when i have material only in the cone (appropriate calculations) and when i have material in the cone and the cylinder two (appropriate calculations).For now i dont know the density of the liquid but i think this is not a problem.I gave you all my tank dimensions that would be helpful.My problem right now is the calculations,so if you have a program or it is possible to create one,it would be very helpful so i can see and understand the blocks that are used and the calculations with the numbers. Thank you in advance.Any help would be nice! 
11/17/2020 3:01 PM  
Joined: 2/22/2008 Last visit: 5/10/2024 Posts: 2698 Rating: (206) 
I answer in this new conference. To show you the inaccuracy here an example. We set your sensor to 0..1000mbar, is nearly the same as 50...1000. The maximum height of the sensor is 10,000mm, therefore every mbar the height will grow up 10mm. That's the resolution for the height, but not for the tolerance, this you have to add and is 1.5% of maximum value = 15mbar = 150mm. A calculated height of 400mm may also be 400+/150mm+/10mm in the worst case. What do you think about the calculated volume with this height ? Next step, we think about the height is okay and we look to the cylindric part with diameter of 2m = radius 1m = 10dm. Height 10mm = 0,1dm (dm³ = Liter) The volume is Pi x r" x h, e.g. 3.14 x 100 x 0,1 = 31.4 Liter for every 10mm of height ~ 31.4 kg for water. These are the minimum steps for the volume calculation. Is it precise enough for you ? Regards, Scorp P.S. The only meaningful way to solve your problem with given sensor is an other plc with high resolution analog inputs, e.g. S71212 with additional analog module. But then you also need a display, e.g. KTP400 
Last edited by: Scorp at: 11/17/2020 15:31:04 

11/17/2020 10:11 PM  
Joined: 5/27/2020 Last visit: 4/23/2024 Posts: 5 Rating: (0) 
The calculated volume is ok with this height.Yes it is precise for me. I know that a plc from the larger series would be more suitable for my application,but i have logo and the specific sensor in my hands.So i will give it a try with these.Thank very much for your help! 
11/18/2020 1:19 PM  
Joined: 2/22/2008 Last visit: 5/10/2024 Posts: 2698 Rating: (206) 
Here is a possible version to calculate the volume of your tank. If the density is like cold water, then Liter = kg. Check the values for different heights. Use google to find the formulas for cone and cylinder volume. The main problem in the Logo controller the number range 32768 ... +32767, when you have to calculate with several arithmetic blocks to avoid overflows. You have to setup your analog input number and ip address. Regards, Scorp AttachmentTank2.zip (260 Downloads) 
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