# Coupling of load cell with a plunger

We are using a load cell as shown below, the data sheet for which can be found on this link.

The load cell needs to coupled with a plunger as shown below.

The plunger is supposed to measure the axial force acting on it. Initially, we had just stuck the plunger with the help of glue on top of the load cell. But with this setup, if the force acting is not completely axial, it tends to cause a moment which leads to incorrect measurement of the force.

We are interested in knowing a reliable way of coupling to solve the issue. Also, we would like to know if there is some reading reference available regarding this.

• consider some sort of ball joint. – Solar Mike May 30 '19 at 7:53
• Requesting you to have a look at the latest answer by me (which was a reply to @am304). It gives some more insight into the problem. – SSJ May 31 '19 at 7:06

Could you not make a guide of sort to constrain the plunger action on the load cell to be along the right axis. Something like that (probably can do something better, but that's all I had time to do):

so fairly tight around the diameter of the pin (say 5.5mm hole), and resting on the surfaces of the load cell to ensure perpendicularity. Can the plunger move up and down or does it have to be stuck to the load cell?

Responding to @am304

Actually making a guide would have worked perfectly if the application had involved measuring vertical axial force. In our case, the whole assembly is supposed to be horizontal with the purpose of measuring the horizontal axial force. The image shown below will explain it.

I feel that although the distributive load acting on the plunger due to the guide causes a moment, it will cause an error in the measurement of the axial force to some extent since we plan on having the least count of 100 mgs (milligrams). I am not sure about how true this is. But it feels like it will have an impact in the magnitude of the force calculated by the plunger. It was also seen while doing a check on the load cell that the same weight placed at the centre of the load cell and at the periphery was giving a

What do you feel about it? Also, is there any way I can eliminate this moment?

P.S. - The plunger can have a relative movement w.r.t. load cell and need not be stuck to it.