Hi,

Our weighing scale (HSC350) is not working properly.maximum weight we have to weigh is 1500g. But without any load the scale shows 1302g.

I have checked the load cell.(HBM PW2DC3MR MAX CAPACITY 7.2 KG). The result is as shown below

1. I gave 10v between excitation Positive and negative. Measure output voltage between signal positive and negative which was equal to -6.2mv.
So mv/v= -.62
The data sheet value is + or - 0.1 mv/v

2. Isolation resistance is >2 G ohm (in data sheet). I could not measure it as the multi meter has only Mega ohm range.

3. Resistance between excitation positive and negative is 366 ohm (300-500 ohm in data sheet).

Resistance between signal positive and negative is 365 ohm (300-500 ohm in data sheet).

4. Resistance between excitation + and signal + is 268.7 ohm.
Resistance between excitation + and signal + is 280.7 ohm.
I think the difference between them should be <= 1 ohm but it is 12 ohm.

First time i am dealing with a problem like this so i need your valuable suggestion to confirm whether the load cell is good or bad.

Regards
sreevin

 

It is possible your load cell has been overstressed to give it a permanent deflection (bent out of shape) Take all the load off it and measure again it should be close to spec.

 

Thanks for your reply. The above given results are obtained by removing all the load and taking the load cell out of the system. So can I confirm that the load cell is damaged?

Regards
sreevin

 

> So can I confirm that the load cell is damaged?

I hate to say it without hands on experience... but it sure appears that way from here.

 

Thanks for the reply.

 

The load cell should be designed with some form of mechanical stop that will make contact to divert the stress when the cell is overloaded.