Cattle weighing scales durability?

amens

How long can you expect the load bars in scales to last?


I bought a scales in 2010 with two MP600 loadbars. It's used maybe five or six times a year to weigh 20 cattle at a time. It's not bolted down or chained, just lying in the crush. Occasionally an animal might push it back a few inches and a few cattle might jump around a bit while on it but nothing very extreme. I used to store the scales in the shed against the wall until 2016 and I lent it out a few times.


In 2016 I used it in the spring without any trouble and when I went to use it in the summer one load bar had an underload or overload error message, can't remember which. Took it back to where I bought it and was told a strain gauge had detached and I can buy a new load bar for €340. So I thought I'm not spending this every few years so no more lending out and after every use remove the load bars and put them in a dry house for storage.


This year I used the scales in february and again no issue. Need to weigh the cows and calves soon for BEEP so just tested the load bars and the other original one is now showing an error on the display like 2 OL and then OUER which I presume means overload. I'll take it back to be looked at but I can imagine what I'll be told: €400 for a new load bar.



The scales was expensive enough to begin with for the amount of use it gets. How often am I supposed to buy new load bars?

patsy_mccabe

Out of interest, what make was it?

amens

Tru-test makes the MP600 load bars.

patsy_mccabe

In this country, anything electrical needs to be kept indoors when not turned on. Sealed or not, moisture will get in there somehow and destroy it.

cute geoge

I taught tru test were the dogs danglers surely mad sucklers leaping on them does no good either

aphextwit

6 Trutest bars permanently under crushs in my care for eight years. One load cell failed last year. I regard that as good compared to previous equipment. Do not apply blast of pressure washer is the maintenance guidance I was given.

Cavanjack

I’d say you would get load cells on eBay a lot cheaper than that.

amens

Cavanjack wrote: »

I’d say you would get load cells on eBay a lot cheaper than that.

I'd say you'd get all sorts of crap on ebay. I had a search and couldn't find anything that looked similar. It would have to have the right dimensions and holes in the right places and it would have to work with the existing eziweigh meter. It would be beyond me anyway.


I took out the old load cell and it has four strain guages that are sealed in a spongy material. There was no sign of any obvious damage. There were signs of spiders or insects having been inside the bar itself but outside the cell. They seem to come up where the rubber feet are attached. You can't really remove this sealing material without damaging the delicate wires underneath so I wouldnt know afterwards if the damage had already been there before removing the material.


The rubber feet have deteriorated and the rusty steel underneath the rubber was touching the ground in parts. I'm thinking that maybe this resulted in less dissipation of shocks when animals jumped on it causing maybe an overloading of the cell.



In the past year or so I did notice at times that even when an animal was standing quietly on the scales the reading could keep varying by 10 or 20kg . Maybe it was beginning to fail then.


I think I'll just buy another loadbar with new feet. I'll close the crush gate from now on so they don't get trapped in the gate and struggle to get free while on the platfrom. Might cover it in **** or straw or something so it's not bright and shiny either so they don't notice it as much and calm down a bit when getting on it. After weighiing I'll remove the bars, wrap in plastic and take indoors.

amens

Just an update on this. There are four pairs of wires, with a pair going to each strain gauge. They are joined together in a wheatstone bridge on a circuit board in the middle of the load cell. There must be an amplifier built in as well which boosts mV output signals to V. I stripped away all the insulation around this board. The eziweigh meter inputs a 5V signal on black and red wires and there are white and green signal wires with a voltage of 2.5V when you turn on the meter. This should be 0V when all four strain gauges have the same resistance. Measuring the resistance of each pair of wires gets you 350Ohm for three of the pairs and 900Ohm for the other pair. 350Ohm is apparently a common value for strain gauges. I dug out the strain gauge that was 900 and the wires from the gauge are so flimsy that they break in the process if not broken beforehand. At least one of them must have been broken before because when I measure the resistance of the strain gauge directly I get 350 Ohm. This 900Ohm even persisted when the pair of wires were no longer connected to the gauge and many other components on the board seemed to have a similar value even though they shouldnt be connected at all. I dug out the circuit board and it is was stuck to a pad underneath. I measured the resistance of that pad and it was zero. Must be all moist. Paring back the insulation on some of the pairs of wires the bare wires all look very green so more corrosion.



If I could solder some wires back on the strain gauge pads I could maybe get the thing working again but it would be a very delicate job. If the load cell had really been overloaded it would be physically deformed and could never be used again. In this case I'd expect the strain gauges to be stretched as well and show a different value than 350Ohm. But even when stretched fully the resistance only changes by a tiny amount and my multimeter mightnt pick it up. The wheatstone bridge is used because it is very sensitive to slight changes in the resistance.


If I see a cheap soldering iron in lidl I might give it a go. In the meantime new loadbar and keep it away from moist air. Datasheet says it's rated to 95% humidity. Ireland must be at least 99% in the winter. You'd wonder how the load cells installed permanently in sheds survive.

patsy_mccabe

I remember mounting a strain gauge in college years ago. They are extremely delicate from what I remember. Any point in looking closely with a magnifying glass?
You could bring the loadcell indoors and see if drying it out slowly over time helps.

_Brian

We bought the whole kit on Amazon for about €375 delivered. €80 for steel to make platform.

Lift it and store away when not in use.

The environment in a crush isn’t great for delicate electronics.