Load Sensor – 50kg – Digital Strain Gauge Weight Sensor – SparkFun SEN-10245
This load sensor is the same as you’d find in a set of digital bathroom scales.
This sensor can measure up to about 50Kg (110 pounds).
Check the video below for a simple explanation of how these work and how to use them.
Load Sensor Specifications:
- Capacity: 40-50 kg
- Comprehensive Error: 0.05 mv/v
- Output Sensitivity: 1.0 ±0.1 mv/v
- Nonlinearity: 0.03 %FS
- Repeatability: 0.03 %FS
- Hysteresis: 0.03 %FS
- Creep: 0.03 (3min)%FS
- Zero Drift: 0.03 (1min)%FS
- Temp. Effect on Zero: 1 %FS/10 ℃
- Temp. Effect on Output: 0.05 %FS/10℃
- Zero Output: ±0.1 mV/V
- Input Resistance: 1000 ±20 Ω
- Output Resistance: 1000 ±20 Ω
- Insulation Resistance: ≥5000 MΩ
- Excitation Voltage: ≤10 V
- Operation Temp. Range: 0--+50 ℃
- Overload Capacity: 150 %FS
NerdKids Video Tutorial:
The NerdKids took a cheap digital scale and hooked it up to an amplifier and a microcontroller. This video outlines them taking apart the scale, wiring it to the amplifier as well as coding. There is also a great overview of the concepts behind strain gauges and Wheatstone bridges. Check out the demo of two live scale apps written in Python near the end of the video.
Note: there’s a lot going on in this project, from the cantilever bending to the bridge noise cancellation to the PC graphics code. It’s a complicated one, so take it slow.
You can download the microcontroller source code. (Start with one of the projects included with the kit, and modify the Makefile to reference this file.) You can also see the source code for the PC-side software, live scale graph and live can counter.