How to increase the sensing area of weight sensor?

Hi,
I want to use the parallel beam load sensor for detecting the weight on a surface. As the sensor size is small and the surface which need to be weighed is large I thought of making a platform for the sensor so that it will be able to sense the entire surface. But I need assistance in doing so. Can anyone please help me? If there is any alternate way of measuring also please let me know. Quick response is appreciated friends. :slight_smile:

Regards,
HemaChowdary

HemaChowdary:
Hi,
I want to use the parallel beam load sensor for detecting the weight on a surface. As the sensor size is small and the surface which need to be weighed is large I thought of making a platform for the sensor so that it will be able to sense the entire surface. But I need assistance in doing so. Can anyone please help me? If there is any alternate way of measuring also please let me know. Quick response is appreciated friends. :slight_smile:

Regards,
HemaChowdary

Any specific load cell has a given maximum weight it can sense before damage (deformed) to the load cell can happen. I've seen applications where the support the weight to be measured on a platform that rests on three or four identical load cells and the measurement is the sum of all 3 or 4 load cells (this is done in your software).

So do you know the maximum weight your cell is rated at? What weight range do you wish to measure?

Lefty

retrolefty:
I've seen applications where the support the weight to be measured on a platform that rests on three or four identical load cells and the measurement is the sum of all 3 or 4 load cells (this is done in your software).

This is how most electronic "personal" ("bathroom") scales now work - a perfect solution to the problem of achieving a "parallel action" in scales by removing all mechanical linkages.

Lefty
These are some the specification of my load sensor.
Rated Load(kg):50kg;
Rated Output(mv/v):2±0.1;
Non-linearity(%FS):0.03;
Hysteresis(%FS):0.03;
Repeatability:(%FS):0.01;
Safe Overload(%FS):120;
Ultimate Overload(%FS):150;

I want to weigh up to a maximum of 50 kg. The idea of taking three or four load cells for measuring weight is good but as far as my knowledge is concerned it will become expensive ..using 3-4 load cells for single surface...

Moderator edit: smileys turned off

HemaChowdary:
Lefty
These are some the specification of my load sensor.
Rated Load(kg):50kg;
Rated Output(mv/v):2±0.1;
Non-linearity(%FS):0.03;
Hysteresis(%FS):0.03;
Repeatability:(%FS):0.01;
Safe Overload(%FS):120;
Ultimate Overload(%FS):150;

I want to weigh up to a maximum of 50 kg. The idea of taking three or four load cells for measuring weight is good but as far as my knowledge is concerned it will become expensive ..using 3-4 load cells for single surface...

Moderator edit: smileys turned off

Well then unless you want to design and build a mechanical platform base that will balance on a single point, I would think about mounting the load cell above the platform suspended by a cable and then cable from the load cell to the platform. Call it a hoist scale.

Lefty

Lefty
Whatever you are saying is ok. But will it be ok if I take a wooden/ aluminium surface and attach this parallel load beam sensor exactly at the centre of the board. will it give me the precise readings?

HemaChowdary:
Lefty
Whatever you are saying is ok. But will it be ok if I take a wooden/ aluminium surface and attach this parallel load beam sensor exactly at the centre of the board. will it give me the precise readings?

Yes, but will it be mechanically stable? Will you have to fuzz with positioning the stuff to be measured just right to prevent 'unbalancing' the platform? There should be mechanical stops added on the bottom of the surface that will 'bottom out' before applying too much off centered weight on the surface in any direction other then straight down. Also keep in mind that the wooden/aluminium surface will itself present a fixed weight to the load cell and will have to be factored out in software, this is called tare weight and it takes away from the maximum weight you can measure before exceeding the load cell's rating.

If I fix rubber stoppers at all the four corners of my wooden/aluminium platform and attach the sensor at the center, will it be stable? Also can u please suggest me any low cost sensor ..if available. I want to measure the large surface area(100cm*100cm)

The point is made that if you have a platform that size, you will simply be unable to balance any load on it without it tipping over in some direction.

Clearly if it tips over and leans on any of those rubber stoppers, the weight is being taken by the stopper and not your load cell, so you cannot be measuring the weight.

There are three solutions. Build a precision lever system using knife edge bearings to transfer the weight (in proportion) from the platform to your load cell - as is done in many and all older commercial scales; use a suspension to hang all of the load from above and mount the load cell in the suspension; or use three (minimum - triangular) or four load cells at the corners of your platform.

Almost certainly, the third of these will prove to be the cheapest. In fact, if cost is a limiting factor, you could consider the purchase and adaptation of a set of $10 bathroom scales (rated to 150 kg). The "feet" can be separated and re-wired to operate at a wider distance.