Load cells, strain gauges, and tactile sensors for robotics, structural testing, and industrial scales.
Another key application of data acquisition is the measurement of force in a system. Knowing the amount of force being experienced at various points in a system is crucial to many areas, such as robotic tactile sensing, payload condition assessments, drilling and extraction systems, as well as industrial scales. One example of force measurement application is in the diagnosis of bearing faults in mechanical systems. In 2014 a new method was developed to better understand the nature of bearing faulting by a combined use of a load cell and an accelerometer. Upon conclusion of the study, it was found that the accelerometer shed light on the location of the fault, whereas the load cell was critical to identifying good bearings from defective ones before they were ever used in a construction. In this case, force detection was the difference between a failed system and a successful one.
Load cells are the sensors used to measure force. These sensors come in many different forms, each customized to suit a desired level of accuracy, sensitivity, or physical integration situation. Load cells additionally have differing numbers of measurement axes. For example, the S-type load cell pictured can only measure stretch or compression along one axis, whereas the disc load cell can measure multiple axes of force. When using a load cell, amplification is another consideration. The load cells themselves output a signal in the millivolt range, and thus must be amplified in order to be read by the Nyquist. It is possible to determine the force through conversion of the output voltage based on the load cell’s excitation voltage proportion, which varies depending on the sensor and is represented by raw millivolt signal in a ratio with amplified voltage. Then, through simple unit conversions the desired output units can be achieved. Additionally, different amplifiers have different gains, and some are adjustable to reach the user’s desired gain. Regarding interfacing with any Nyquist model, a load cell (by way of an amplifier) uses an analog input, and can be powered by a varying range of voltages.
4 M.S. Safizadeh, S.K. Latifi, “Using multi-sensor data fusion for vibration fault diagnosis of rolling element bearings by accelerometer and load cell,” Information Fusion, Volume 18, 2014, Pages 1-8, ISSN 1566-2535
Recommended DAQ
Recommended DAQ: Nyquist 3
Load cells produce mV-level differential signals. NQ3’s 18-bit fully differential ±10 V input is built for this — pair it with one of our load-cell amplifiers from the Tacuna Systems catalog.
Code example
The DAQiFi Python SDK exposes a property-based API. Below is a minimal stream — discover the device, enable an analog-input channel, and print samples at 1 kS/s.
from daqifi import DAQiFiDevice
with DAQiFiDevice.discover_first() as dev:
dev.channels.ai0.enable()
for sample in dev.stream(rate_hz=1000):
print(sample)
For C#, Java, LabVIEW, or Node.js examples, see the open-source stack page or jump straight into the reference example app on GitHub.
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