7 questions about force sensors that you want to know the answer to

The basic element of each electronic scale as well as other devices measuring compression and tensile forces, stresses, etc. are strain gauges, commonly known as strain gauges. Currently, the most widely used are resistance sensors, which are characterized by many advantages, such as high sensitivity and accuracy, small dimensions, resistance to vibrations and shocks, and the ability to work at high temperatures and pressures. When choosing a sensor for the application, you should answer a few important questions. Below are answers to the most common ones.

1. What is sensor sensitivity and what units are used to measure it?

The sensitivity of a strain gauge force sensor is expressed in mV/V (millivolt per volt) and is equal to the output voltage of the sensor with a 1V supply and nominal load. Standard sensors are produced with a sensitivity of 1 mV/V to 3 mV/V, of which the most common are sensors with a sensitivity of 2 mV/V or 1.5 mV/V. Data sheets contain nominal values.

The exact value may slightly differ from the nominal value by several percent. For example, a sensor with a nominal sensitivity of 2 mV/V may have an exact value of 1.9836 mV/V. The exact value is given in the protocol supplied with the sensor.

2. How to calculate the output voltage of the sensor?

The output voltage of the sensor depends on three factors:

• sensor sensitivity C(mV/V)
• sensor supply voltage Uc(V)
• load force Fx

The output voltage of a sensor with a nominal range of Fn can be calculated using this formula: Us = (C * Uc * Fx) / Fn.

Example. The sensitivity of the sensor is C = 1.9836 mV/V, range Fn = 5 kN. The sensor is supplied with 10 V DC and loaded with a force Fx = 3.5 kN. The output voltage will be: Us = (1.9836 * 10 * 3.5) / 5 = 13.89 mV. If Fn = 0 kN, the output voltage is Us = 0 mV. If the nominal range Fx = Fn = 5 kN, then Us = 19.836 mV. This means that the output voltage depends on the load and varies linearly in the range of 0… 19.836 mV. Note: The zero state of the sensor is ignored in the calculations.

3. How to choose the optimal sensor range?

The measured force must never exceed the range specified by the sensor manufacturer, even for a short time. This may cause permanent damage to the sensor. For this reason, we do not recommend using the entire range of the sensor, but rather keeping a reserve. For static loads, we recommend that the force should not exceed 75% of the range and for dynamic loads, 50% of the range.

4. What is the difference between an aluminum sensor and a stainless steel sensor?

The type of material from which the sensor body is made is selected depending on the range of the sensor. In general, sensors made of aluminum are less suitable for permanent loads because they have a higher creep factor.

5. What is the difference in the direction of the applied force?

Each force sensor can measure force in the compression and extension directions. The only limitation is their mechanical design, for example the lack of threads for the sensor to be pulled. Sensors manufactured by EMSYST are calibrated in one force direction. This means that the measurement in the opposite direction will be slightly more inaccurate. The calibration direction is specified by the customer when ordering.

6. How accurate are the force sensors?

The accuracy of the sensors is expressed by the accuracy class. The EMSYST company manufactures sensors with an accuracy class of 0.5 and 0.2. Example: For a sensor with a range of 1kN and an accuracy class of 0.2, the error is ± 2N.

7. What is the purpose of using a signal booster?

The output from the strain gauge force sensor depends on its sensitivity and supply voltage. It is usually equal to a few millivolts. The signal amplifier amplifies this output voltage to the level of the industrial standard (0… 10 V) or converts it to a current output (4… 20 mA), and also supplies the sensor with a stable supply voltage. The sensor can work and make measurements even without a signal amplifier, but the most common combination is: a sensor with an amplifier.

Detailed information about force sensors in our offer can be found on this page.

Check also the offer of measuring devices for sensors strength and boosters you can buy in our online store.

Still have questions? Contact our consultants who will help you choose the right solution.

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