Excitation voltage 101

Excitation is an electrical signal. The excitation voltage is represented by the volts direct current (VDC). The direct current only flows in one direction. Alternating current (AC) temporarily changes direction.

Load cell excitation provides a voltage to produce an output signal, sometimes referred to as “supplying” the load cell. The output signal of a load cell is typically minimal, so an excitation voltage is required to power the load cell and ensure that the output signal is accurate. The magnitude of the output signal is proportional to the force applied to the load cell. The greater the force, the greater the output signal.

Interface-Load cells contain proprietary Strain gauges, which are attached to a Wheatstone bridge, that is, an electrical circuit that changes resistance when subjected to a load. The Wheatstone Bridge consists of strain gauges arranged in a specific configuration. When a load is applied to the load cell, the strain gauges deform and their resistance changes. This change in resistance causes the output voltage of the Wheatstone bridge to change.

Interface offers electrical performance data for everyone Specifications, represented as VDC MAX, if applicable. Excitation voltage data is listed in the electrical section of a converter model's specification data sheet, along with other factors including power rating, bridge resistance, and zero balance.

Tips on sensor performance and excitation

Load cell excitation is necessary to ensure the accuracy and reliability of load cell measurements. Below are some tips to consider when developing a force measurement system related to excitation and power signals:

• The output signal of a load cell is given in millivolts per volt (mv/V) of excitation voltage at capacity.
• The excitation voltage also influences the size of the output signal. A higher excitation voltage produces a higher output signal.
• The output signal is directly influenced by the input voltage. It is important to maintain a stable excitation voltage.
• Interface's load cells all contain a full bridge circuit. Each leg has a typical bridge resistance of 350 ohms, except for models like our 1500 which have 700 ohm legs.
• The preferred excitation voltage is 10 VDC, which ensures close agreement with the original calibration performed at Interface prior to shipment from our factory.
• A DAQ system does not always provide a stable excitation voltage. Consider using a signal conditioner or a DAQ system with dedicated bridge inputs.

Why load cell excitation is important

Excitation is important in force measurement applications because it provides the energy required to operate the load cell and ensures an accurate output signal. Without excitation, the load cell cannot produce an output signal and the force measurement will be inaccurate. It also affects accuracy, noise and range.

Accuracy: The excitation voltage powers the load cell and ensures an accurate output signal.

Noise reduction: The excitation voltage can help reduce the noise in the output signal.

Range: The excitation voltage can help extend the measurement limit of the load cell.

The excitation voltage should be applied uniformly to the load cell. This means that the excitation voltage should be applied to both sides of the load cell. The excitation voltage should be stable. This means that the voltage should not fluctuate or drift over time. The excitation voltage should be filtered. This means that any noise in the excitation voltage should be removed.

Excitation 101 in force measurement

The excitation voltage determines the sensitivity of the load cell. A higher excitation voltage results in a more sensitive load cell, meaning it can measure smaller forces.

The excitation voltage influences the frequency response of the load cell. A higher excitation voltage results in a wider frequency response, meaning the load cell can track force changes more accurately.

Linearity measures how accurately the load cell converts force into an electrical signal. A higher excitation voltage results in a more linear load cell, meaning the output signal is more proportional to the applied force.

The excitation voltage is well regulated to reduce measurement errors. Fluctuations in the excitation voltage can cause a slight shift in the zero point and creep movements. This effect is most noticeable when the excitation voltage is turned on for the first time. The solution is to allow the load cell to stabilize by operating it at a 10 VDC excitation voltage for the time required for the gauge temperatures to reach equilibrium. The effects of fluctuations in excitation voltage are typically not noticed by users except when the voltage is first applied to the cell.