Detailing sensor nominal output millivolts per volt

When measuring force, many sensors and... Device specifications be carefully reviewed to ensure you receive the right solution for your testing project.

We strongly recommend that you carefully review the electrical specifications detailed in the datasheets for all interface force transducers , multi-axis sensors , and reaction torque transducers . This comprehensive understanding of the rated power (RO), excitation voltage , bridge resistance, zero adjustment , and insulation resistance will enable you to select the appropriate sensor for your testing project.

The nominal power is expressed in millivolts per volt (mV/V). This is the electrical power of a load cell, multi-axis sensor or reaction torque transducer in mV/V of excitation at the rated load. It essentially expresses the sensitivity of a load cell. RO represents the change in the output voltage in millivolts of the load cell relative to a change in the excitation voltage applied to it in volts.

For example, the electrical voltage output of an interface load cell with a 4 mV/V output at a rated load of 5.000 lbf is typically characterized as 4 mV ± 10% or 3,6 mV/V to 4,4 mV/V. Depending on the application, a tighter output tolerance may be required. Further examples can be found in our free Interface Load Cell Field Guide.

Before we delve into the meaning of mV/V in load cell specifications, let's learn a few terms from the field of electrical specifications. These terms, such as power rating, excitation voltage and nonlinearity, are not just technical jargon. They directly affect the performance of your load cell. Understanding mV/V and other technical aspects of load cell design will help you select the load cell that best suits your application and ensures precise and accurate force measurements.

• Rated power: The output corresponding to the capacity is equal to the algebraic difference between the signal at (minimum load + capacity) and the signal at minimum load. This indicates the maximum output voltage the load cell will produce at full capacity.
• Excitation voltage: The load sensors contact a full bridge circuit. Each leg is typically 350 ohms, with the exception of Interface's 1500 models, which are 700 ohms. The preferred excitation voltage is 10 VDC, which guarantees the best agreement with the original calibration performed in Interface's calibration laboratory. The voltage supplied to the load sensor powers its internal strain gauges.
• Nonlinearity: The algebraic difference between the power at a given load and the corresponding point on the line between minimum and maximum load. Normally it is expressed in %FS. Characterization is usually measured at 40-60%FS. The relationship between applied force and output voltage may not be linear, especially at high or low forces. The load cell specifications usually contain information about nonlinearity.

In our Interface 101 series you will find detailed information on the most important specifications, products, technical topics and basics of sensor technology.

Why mV/V is important

• Relates Force to Electrical Signal: The mV/V rating helps you understand how much force is required to produce a given output voltage. A higher mV/V value indicates a more sensitive load cell, producing a larger voltage change with a lower force.
• Calibration and Accuracy: Because mV/V is a ratiometric measurement, errors due to excitation voltage fluctuations are minimized. This is because the output voltage changes in proportion to the excitation voltage. Many devices can perform ratiometric measurements, resulting in more accurate readings.
• Choosing the right load sensor: When choosing a force sensor, consider the desired level of sensitivity. A higher mV/V value is preferred for high-precision measurements of small forces. However, for heavy applications with high forces, a lower mV/V value may also be sufficient.

TIP: The interface can standardize outputs within ±0,1% of the rated outputs specified on the product specification datasheet. This would mean that the 4 mV/V output would be standardized to 3,996 mV/V to 4,004 mV/V.)

Understanding electrical specifications like mV/V will help you choose the right solution for your application. Tune in to our webinar, "Demystifying Specifications ." If you have any further questions about mV/V or other electrical specifications on our product specification sheets, please feel free to contact us.