Applying 5 kN external force on a load cell - Force readings to start from 0 kN

I am recording readings from an Omega Load Cell using DAQmx (Continuous bridge example) . A pre-tension force of 5 KN is applied on the load cell. Is there any way of forcing the applied pre-load force to drop to zero so the readings to start from zero?
Thanks!

The way you worded your question in somewhat ambiguous.
You really do not want to remove the physical preload force, do you?
I think what you want to do is to change the readings to account for the preload. That can be done fairly easily if you have complete control over the applied loads and know when there is no additonal load on the cell. In the weighing (scale and balance measurements of force or mass) this process is called taring. The tare is the weight or force without the external load. At the grocery store they adjust for the weight of the container before they add your food.
Add a Tare state to your state machine. When the user presses the Tare button on the front panel, the program takes a reading from the load cell (or several readings to be averaged). That reading is the tare force. Place it on a shift register. Then subtract the tare force from the readings taken while the desired measurements are happening.
If the maximum load is close to the load cell limit, the termperature of the load cell varies, or there are impact loads involved, then this simple taring approach may not be good enough. That is not because of any inherent problem with the method, but due to the things that can cause a load cell to drift or change baseline outputs.
Lynn

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Force Measurement v1.vi ‏106 KB
Modified Load Cell.png ‏267 KB

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