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Institute for Measurement Technology
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Bachelor Theses.

Mobile Data Recorder for Signals of Strain Gauge Sensors

Karl Zeilhofer

A field-compatible data recorder was developed and built.

 

Figure 1: The recorder is integrated in a waterproof case. Here you can see the inserted batteries, the touch display and the rugged connectors on the side.

Up to eight sensors based on strain gauges, such as load cells, can be digitized and recorded.
Up to 4800 samples per second are possible per channel, with a resolution of at least 20,000 steps being achieved.
With optional digital low-pass filtering and sampling rate reduction, the resolution can be increased to 200,000 steps with 5 samples per second.
The synchronous sampling of all channels enables the calculation of multi-dimensional force vectors through the use of multi-axis force sensors.
Two of the eight channels can optionally also be used as inputs for temperature sensors. Pt-100, Pt-1000 and type K thermocouples are supported.
If necessary, several devices can be synchronized via a fast RS-485 bus in order to expand the number of channels to practically any number.
The recorded measurement data is stored on a USB flash drive in a text based CSV format.
The device is operated via a capacitive touch display that is controlled by a Raspberry Pi.
It is powered by lithium-ion batteries.
All electronics are housed in a waterproof and dustproof case, which enables a wide range of applications.
Including the connectors for the sensors it achieves the protection class IP67.

Youtube Video about Setup and Demonstration of the Data Recorder

Keywords: Strain gauges, load cells, Raspberry Pi, Arduino, lithium ion battery, deep discharge protection, AD7190

September 30th, 2020