Load Cell Specifications and troubleshooting - Page 1
Forum section: electronics / general

author: BrendanDixon
author_rank: Newbie
timestamp: March 09, 2023, 06:08:27 pm
content: Hi All,We have a weighbridge supplied by Schenck Process. Last year we had a flood and the weighbridge was flooded for a week or 2. The Weighbridge consists of 24 x 15Ton load cells and 8 controller boxes what convert the signals to Ethernet so that the software on a computer can read the values. Our advice was that all the controllers will need to be replaced. Management were like we cannot wait, we need to get the weighbridge working right away. We must clean all the electronics and it will work again. We did this and miraculously the weighbridge is mostly working. Although it breaks down weekly and we have to keep swapping cards around to try and get them to work again. There is one load cell that does not work though. We did find damage to the cable right as it enters the load cell and if we get the cable at the right angle it may sometimes work. I although I am not sure of the accuracy. The weighbridge is now due for calibration and the oem said they cannot calibrate with a faulty load cell. but management do not want to wait for a new load cell. Said we must repair the cable and put it back. we have joined the cable. I cannot be replaced as it is glued into the load cell. We did do some testing and found the following.Specifications Input resistance is 386ohm +/-3ohm. The reading we got was 389ohm. on the bordelineSpecifications Output resistance is 360ohm +/-0.5ohm. The reading we got was 362.7ohm. This is way over specification.Our new boss phoned a friend who said the resistance does not matter. We also do not need to worry about torquing the bolts. It is fine as long as they are tight.Is there anyone here that knows allot about load cells that can tell me if the readings that we got will be ok? We are paying allot of money for the calibration, and in my opinion is that the oem is going to fail the weighbridge, or the parts may fail as we are struggling to keep them working. and that this whole exercise is pointless as we are having so much problems with the weighbridge and management are not interested in replacing the parts.

author: mendip_discovery
author_rank: Super Contributor
timestamp: March 09, 2023, 08:36:23 pm
content: Quick way to check it.Take another cell off, stack it ontop. Use your hydraulic press and see if they give a similar reading.Load cells work of a wheatstone bridge. Have a Google for more.I would just do your best and let the boss deal with the fall out from the calibration when they say its ducked.

author: BrendanDixon
author_rank: Newbie
timestamp: March 09, 2023, 08:54:43 pm
content: We do have a load cell and jig that we can test. but my opinion it is too much effort to prove. Was just wondering how important the resistance reading was as the tolerance shows 0.5Ohms and we were getting 2.7ohm which is 2.2 ohm over the tolerance.

author: wraper
author_rank: Unknown
timestamp: March 09, 2023, 09:19:08 pm
content: Resistance precision does not mean a shit. The major things that matter are: if there is no too large zero offset (resistive bridge is well balanced), if it's sensitivity and linearity are within spec. And that it does not creep under load too much.