Raul Posted August 11, 2011 Report Share Posted August 11, 2011 Everything is working fine with the loadcells except for a little oscillation. I have read the help file but I need more details and I did not find an example or useful topic in the forums regarding Auto zero tracking. This would really help me to get the precision I need by eliminating those little variations near the zero point. I'm attaching the application just in case you want to review it. I'm having problems defining the LC tracking band, LC tacking range and the LC motion band values. Not sure if I should use constants or MLs for this. Thank you. (The scale is set up from 0.000 grams to 999.999 grams, The oscillation is minimal but it prevents me from acquiring accurate data once it starts escalating.) V130_Celdas antes de auto zero.vlp Quote Link to comment Share on other sites More sharing options...
Raul Posted August 25, 2011 Author Report Share Posted August 25, 2011 Ideas anyone? I have contacted experienced PLC programmers in my country but none of them are familiar with this particular detail with Unitronics. Quote Link to comment Share on other sites More sharing options...
Damian Posted August 26, 2011 Report Share Posted August 26, 2011 Please explain in detail you oscillation. What is the frequency and amplitude? Is it sinusoidal or random? What type of excitation are you using? Are you viewing just the value on the HMI, or are you looking at it with a scope? What are you using as a power supply for the V130 and the LC1 module? Gives details on how the power wiring was done between the expansion modules, the V130, and the power supply. What type of wire? Shieled? Twisted? Floating common? Daisy chained or both directly back to the power supply. Distance between load cell and LC1? Is the Power supply sourcing anything else? Are you using and EX-A1 or EX-A2? Where are you adjusting the tracking band, range, and motion band? Are you in a lab setting or are you in an industrial environment that may have a lot of noise sources? What degree of accuracy are you expecting? The more info you give us the better the odds we can help. Quote Link to comment Share on other sites More sharing options...
Raul Posted August 26, 2011 Author Report Share Posted August 26, 2011 Hello, I don't have the means to measure frequency or waveform. Excitation is AC I am viewing the value on the HMI only. AC Voltage reading between +SG and +E is 2.4 V with or without load, same goes for -SG and -E. If measured as DC it oscillates between -5 mV and 5 mV. AC power is connected to a main switch then a fuse and then it goes into the power supply. The power supply is a Weidmuller CP SNT 70W 24V 3A. There is a fuse and then the EX-A1, then both IO-LC1's and then the PLC. (Daisy chained with 20AWG 600 V plastic coated copper wire). Only AC is grounded at the main switch. The distance between the loadcell and LC1 is less than 3 feet, the loadcells cable was not modified at all. It is a 4 wire cable, connected according to the LC1's wiring diagram for 4 cable loadcells. The power supply does not source anything other than what has been mentioned above. Tracking band, range and motion band were adjusted on the computer and fed to the PLC. The function is not present on the file I uploaded but they were located on the Loadcell calibration subroutine that is activated when you press the F1 key on the PLC and the HMI goes to the Loadcell calibration screen. I am located inside an empty warehouse, there are no engines, fluorescent lights, leds or anything that could cause interference. The power lines are only feeding this system right now, everything else has been disconnected. There is a 1HP water pump connected to the system but it is currently off. I am measuring thousandths of grams 000.000 up to 150 grams. The loadcell has been calibrated with 4 points. (0 grams, 10.6 grams, 18.9 grams and 143.9 grams) All weights were measured with lab equipment. Their weights remain more or less stable but the rightmost digit has the variation. If I reduce the number of digits, the variation moves to whatever the rightmost digit is. I tried rounding it, but the last digit remains constant and the next digit to its left inherits the variation. My personal guess was that the oscillation is due to the small mV variations that exist around the zero so I wanted to give the auto zero tracking function a try, but unfortunately I can't get it to work. Please bare with me, this is my first PLC project and I have read, studied, learned and re-read almost everything there is to Unitronics regarding this subject. Thank you. Quote Link to comment Share on other sites More sharing options...
Gabriel Franco Posted August 26, 2011 Report Share Posted August 26, 2011 Some ideas you can try: - Check entire system for mechanical oscillations or obstructions which causeyour issue. - Have you tried loadcell filter & round FB? - Keep in mind your loadcell accuracy according with its class, so you do not getmuch more counts than loadcell can give, even module is capable to do. - Is your scale a platform, an automatic weighing device or manual one? Basedon it, you can set proper values for filters and tracking values - Use raw or uV representation to figure out how large your oscillations are. Quote Link to comment Share on other sites More sharing options...
Damian Posted August 30, 2011 Report Share Posted August 30, 2011 Hello, I don't have the means to measure frequency or waveform. Excitation is AC I am viewing the value on the HMI only. AC Voltage reading between +SG and +E is 2.4 V with or without load, same goes for -SG and -E. If measured as DC it oscillates between -5 mV and 5 mV. AC power is connected to a main switch then a fuse and then it goes into the power supply. The power supply is a Weidmuller CP SNT 70W 24V 3A. There is a fuse and then the EX-A1, then both IO-LC1's and then the PLC. (Daisy chained with 20AWG 600 V plastic coated copper wire). Only AC is grounded at the main switch. The distance between the loadcell and LC1 is less than 3 feet, the loadcells cable was not modified at all. It is a 4 wire cable, connected according to the LC1's wiring diagram for 4 cable loadcells. The power supply does not source anything other than what has been mentioned above. Tracking band, range and motion band were adjusted on the computer and fed to the PLC. The function is not present on the file I uploaded but they were located on the Loadcell calibration subroutine that is activated when you press the F1 key on the PLC and the HMI goes to the Loadcell calibration screen. I am located inside an empty warehouse, there are no engines, fluorescent lights, leds or anything that could cause interference. The power lines are only feeding this system right now, everything else has been disconnected. There is a 1HP water pump connected to the system but it is currently off. I am measuring thousandths of grams 000.000 up to 150 grams. The loadcell has been calibrated with 4 points. (0 grams, 10.6 grams, 18.9 grams and 143.9 grams) All weights were measured with lab equipment. Their weights remain more or less stable but the rightmost digit has the variation. If I reduce the number of digits, the variation moves to whatever the rightmost digit is. I tried rounding it, but the last digit remains constant and the next digit to its left inherits the variation. My personal guess was that the oscillation is due to the small mV variations that exist around the zero so I wanted to give the auto zero tracking function a try, but unfortunately I can't get it to work. Please bare with me, this is my first PLC project and I have read, studied, learned and re-read almost everything there is to Unitronics regarding this subject. Thank you. Your comment about the oscillation in the rightmost digit regarless of your resolution does sound a bit flakey. I have an LC1 module and V130 here. When I get a chance I'll download your program and see if I can't duplicate the phenomena. D Quote Link to comment Share on other sites More sharing options...
Raul Posted August 30, 2011 Author Report Share Posted August 30, 2011 Your comment about the oscillation in the rightmost digit regarless of your resolution does sound a bit flakey. I have an LC1 module and V130 here. When I get a chance I'll download your program and see if I can't duplicate the phenomena. D Can I assume then that auto zero tracking will not solve this issue? Quote Link to comment Share on other sites More sharing options...
Raul Posted August 30, 2011 Author Report Share Posted August 30, 2011 Can I assume then that auto zero tracking will not solve this issue? I added the rounding and filter function. I get a single reading now but every time I get to the part where the program reads weight, it gives a different reading with the exact same weight. I can only think the oscillation is still present due to the range of values I get on every reading. Quote Link to comment Share on other sites More sharing options...
luisedano Posted April 8, 2016 Report Share Posted April 8, 2016 hello happy to say hello .... excuse me I have the same problem you have me gustria saver if you managed to fix it .. Quote Link to comment Share on other sites More sharing options...
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