How to get force feedback from PG70 gripper?

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Hi,

I am using PG70 gripper with schunk LWA4P arm. I am using ROS for my development. PG70 manual mentions that it has a range for gripping force from 30-200 N. This can help in varying the way how gripper can hold different objects. For example, force applied to hold a plastic object, a glass object and a rubber object has to be different.

So can anyone please help me in getting gripping force from PG70 gripper?

Thanks in advance.....