16 November 2017

How does load cell work?

How does load cell work?

What is loadcell?

Load Cell is a device that converts force into electrical signal.

Strain gage based load cell is made of a specially engineered mechanical component called as an element. Four strain gauges are positioned precisely and bonded on to the element using a special adhesive. (strain gauge is a device that changes resistance when it is deformed or stressed).

 

[swf src=”https://kobastar.com/wp-content/uploads/2017/11/sg.swf” height=”150″ width=”400″][/swf]

The force-electrical signal conversion happens in two stages-

  • force applied deforms the element which in turn deforms the strain gauges
  • How does a strain gauge sensor work?
  • strain gauges converts the deformation to electrical signals

The strain gauges are wired in Wheatstone bridge configuration. The bridge is connected to a power supply unit and a signal conditioner through a 4-core cable. When an input voltage (10VDC) is applied to the bridge, the output is a voltage in the range of few millivolts.

[swf src=”https://kobastar.com/wp-content/uploads/2017/11/sglc.swf” height=”250″ width=”600″][/swf]

The load cell output is proportional to the load applied to the element.

Wheatstone Bridge

Wheatstone Bridge

What is sensitivity of load cell?

Basic specifications of a load cell-

  • Capacity (kg)
  • Full scale Output (mV)
  • Sensitivity (mV/V)
  • Excitation Voltage (VDC)
  • Input resistance (ohms)
  • Output resistance (ohms)

What is a load cell calibration?

Below are the commonly used standard values-

  • Excitation voltage: 10V or 12V DC
  • Full scale output: 10mV, 20mV and 30mV
  • Load cell sensitivity: 1mV/V, 2mV/V and 3mV/V
  • Input resistance: 350Ω and 700Ω or 1000Ω
  • Output resistance: 350Ω and 700Ω or 1000Ω
  • Kobastar cable color code:
  • Excitation +  Red
  • Excitation –   Black
  • Signal +         Green
  • Signal –          White
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