What is a Load Cell? How do Load Cells Work?

Sensors are devices (usually electro-mechanical) which help us measure a physical parameter (such as temperature, pressure, force, acceleration etc.) by providing a signal that either quantitatively measures (level) that physical parameter or provides a simple binary signal that indicates a yes/no signal that tells us if something occurred or not (such as a touch sensor). Most sensors require power to be provided to a sensing element and an electrical signal is then generated after the measurement.

What is a load cell?

A load cell is a sensor or a transducer that converts a load or force acting on it into an electronic signal. This electronic signal can be a voltage change, current change or frequency change depending on the type of load cell and circuitry used. There are many different kinds of load cells. We offer resistive load cells and capacitive load cells.

Resistive load cells work on the principle of piezo-resistivity. When a load/force/stress is applied to the sensor, it changes its resistance. This change in resistance leads to a change in output voltage when a input voltage is applied.

Capacitive load cells work on the principle of change of capacitance which is the ability of a system to hold a certain amount of charge when a voltage is applied to it. For common parallel plate capacitors, the capacitance is directly proportional to the amount of overlap of the plates and the dielectric between the plates and inversely proportional to the gap between the plates.

How does a resistive load cell work?

A load cell is made by using an elastic member (with very highly repeatable deflection pattern) to which a number of strain gauges are attached.

In this particular load cell shown to the right, there are a total of four strain gauges that are bonded to the upper and lower surfaces of the load cell.

When the load is applied to the body of a resistive load cell as shown above, the elastic member, deflects as shown and creates a strain at those locations due to the stress applied. As a result, two of the strain gauges are in compression, whereas the other two are in tension.