# Load cells intermittent bad reading



## Funkadelicfred (Jan 30, 2019)

We've got 4 load cells on a scale and every once in a while (according to the operator) they give faulty readings. We've tested the leads in the junction box just before and they all seem to be giving proper signals when we apply weight to the cells. 
My suggestion(as just an apprentice) was to remove one of the cells, wait a week, see if we have strange readings and then reattach and move to the next one until we locate the issue. I thought of this mostly because my boss didn't have any better ideas and we could at least isolate the cell or better yet, prove that it isn't a problem with any of the cells which is my theory.
Has anyone encountered any similar situations with intermittent bad reading on load cells? (and to this point, they've basically all been replaced already) :vs_unimpressed:
I know I'm probably light on information but I'm not sure what is required so ask away and I will supply.


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## macmikeman (Jan 23, 2007)

Something or other about hooking the microwave up to 240 volts and so on.......


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## joebanana (Dec 21, 2010)

Wouldn't it be funny if it wasn't the cell's? Like the transmitter, bad connection, or display.


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## micromind (Aug 11, 2007)

While it could be the cells, it could also be a mechanical issue. 

I've had scales jam up from rocks, etc. making them give bad weights.....cells were fine.


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## Funkadelicfred (Jan 30, 2019)

joebanana said:


> Wouldn't it be funny if it wasn't the cell's? Like the transmitter, bad connection, or display.


Well that's what I'm wondering. We've already replaced most of them and thw issue remains.


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## John Valdes (May 17, 2007)

You can test each one. One at a time to see if all four are good. Its been a long time, but I think it outputs millivolts.
You can read with your meter.


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## Funkadelicfred (Jan 30, 2019)

John Valdes said:


> You can test each one. One at a time to see if all four are good. Its been a long time, but I think it outputs millivolts.
> You can read with your meter.


Yeah that's what we tried. Millivolts and they read properly when stepped on so they work mostly. Just sometimes it doesn't but I guess that's the issue with intermittent problems is that they're really hard to diagnose.


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## pudge565 (Dec 8, 2007)

Funkadelicfred said:


> John Valdes said:
> 
> 
> > You can test each one. One at a time to see if all four are good. Its been a long time, but I think it outputs millivolts.
> ...


Can you describe the procedure you used to test the cells? It isn't as easy as just taking 1 millivolt reading. Load cells use a wheat stone bridge so you have to take multiple readings on each load cell and compare them. I don't remember the specifics but I'm sure I could find them if needed.


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## gpop (May 14, 2018)

I always like to ask what else is going on when a sensor starts to play up. I might even sit there a few hours and watch for myself. 

I have also found that operators come up with strange solutions to problems that sometimes answer there own problems. "when it does that you have to kick it" in mechanical terms means something is getting stuck or electrical terms means a loose wire.


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## 460 Delta (May 9, 2018)

Moisture ingress in the anything, jb, cable insulation, possibly the cell itself will cause erratic readings. R-Mix plants live and die by accurate weight, and water and high PH are everywhere, I change a lot of cables and splice them with epoxy filled underground wire splicers.


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## Funkadelicfred (Jan 30, 2019)

pudge565 said:


> Can you describe the procedure you used to test the cells? It isn't as easy as just taking 1 millivolt reading. Load cells use a wheat stone bridge so you have to take multiple readings on each load cell and compare them. I don't remember the specifics but I'm sure I could find them if needed.


Boss would take a millivolt reading between the two leads of the cell and someone would step on a cell. Then he would compare them with the other ones and see if they're similar.


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## paulengr (Oct 8, 2017)

Take a plant radio and key the mic right next to the load cell. Works almost every time:


Sent from my iPhone using Tapatalk


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## Funkadelicfred (Jan 30, 2019)

paulengr said:


> Take a plant radio and key the mic right next to the load cell. Works almost every time:
> 
> 
> Sent from my iPhone using Tapatalk


Sorry I don't quite understand


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## paulengr (Oct 8, 2017)

Funkadelicfred said:


> Sorry I don't quite understand




Most load cells will react to millivolt interference nearby. Bad ones give different response. But also frequently intermittent unexplained scale errors turn out to be truck drivers with CB radios with huge kickers or plant Motorola style radios transmitting too close to a load cell which acts like an antenna. The hydraulic scales don’t have this issue.


Sent from my iPhone using Tapatalk


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## Funkadelicfred (Jan 30, 2019)

paulengr said:


> Funkadelicfred said:
> 
> 
> > Sorry I don't quite understand
> ...


I don't know enough to argue but this scale is located up 3 flights of stairs away from anything in a plant where there is no radios so I don't think this is it.


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## Jmoney (Aug 24, 2019)

I had similar problem with load cells work intermittently. We changed the summing board and it fixed the problem.


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