Repairing/replacing strain gauge on cattle weighing load cells

Thread Starter

mcsprint71

Joined Nov 13, 2018
5
HI all, I have a cattle weighing system with two x 1000kg load bars. One of them stopped working, so when I measured difference in resistance between two wires (I think there are about 5), each combination showed zero. I tried removing the silicon from around the load cell with heat and wiring of the strain gauge broke off. Was wondering if anyone had a way of removing all the silicon without destroying more of the wiring. Obviously I'll have to replace the broken strain gauge wiring. Not quite sure where to obtain, or how to do, but first things first. Many thanks, James
 

wayneh

Joined Sep 9, 2010
16,400
I have no idea but it may help if you can tell us the manufacturer and post a photo. The more details, the more likely someone may have an idea.
 

ericgibbs

Joined Jan 29, 2010
11,095
hi mcs,
Welcome to AAC.
As already requested more info regarding the scale type.
Look at these 3 PDF's they may give you some background on the problem.
You said I tried removing the silicon from around the load cell with heat and wiring of the strain gauge broke off.

Its unusual to get zero resistance readings from all the cells, its more likely a chopped thru main load cell cabling.

Please post a clear photo of this damaged area.

E
 

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Thread Starter

mcsprint71

Joined Nov 13, 2018
5
I have no idea but it may help if you can tell us the manufacturer and post a photo. The more details, the more likely someone may have an idea.
hi, thanks for your response. It is a Thunderbird PS3000 with 2000kg weigh bars. You can see in this first picture, where I've removed the silicon, I'm pretty sure the strain gauge has come away. I continued to carefully remove the silicon to get to the wires, and realised that a number of the wires must have been broken somewhere along the length of it as there was no continuity. Closer to the plug end, as I pulled the cord through the casing near the plug, it totally broke. There was no damage on the outside. I then got continuity of each wire. But back to the problem of the strain gauge.

IMG_20181114_162808_load cell 1_resize.jpg
 

Thread Starter

mcsprint71

Joined Nov 13, 2018
5
hi mcs,
Welcome to AAC.
As already requested more info regarding the scale type.
Look at these 3 PDF's they may give you some background on the problem.
You said I tried removing the silicon from around the load cell with heat and wiring of the strain gauge broke off.

Its unusual to get zero resistance readings from all the cells, its more likely a chopped thru main load cell cabling.

Please post a clear photo of this damaged area.

E
 

ericgibbs

Joined Jan 29, 2010
11,095
hi 71,
Looking the photo post #4, its damaged beyond repair, the base metal work has rusted away.
When this happens the actual strain gauge element becomes detached.
You need to get down to the bare metal, making sure its a perfectly flat/even surface, the fit a new strain 1000Kg element.
I would replace the strain gauges in both bars, after cleaning the metal surface, use the correct Bonding adhesive for the strain elements.
After the the adhesive is cured, test the cattle scale with a known weight, if it works OK, then add a non corrosive sealant over the elements.
Make sure the lead wires are firmly secured to the metalwork so the gauges don't get ripped off.

Good luck.
E
Rust1.jpg
 
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