# Rapid and Cost-Effective Fabrication and Performance Evaluation of Force-Sensing Resistor Sensors
## 3 Results
### Load Test of the FSR Sensor  
To analyze the sensing characteristics of the manufactured FSR sensor according to load, a five-stage compression test was conducted using the setup shown in Figure 6. In order to perform continuous load tests, equipment was designed and manufactured to apply a fixed load of approximately 1 kg using a weighing holder and weights. First, the load tester was 3D modeled (Figure 6a). It was specifically designed to apply the load by moving 0.01 mm per pulse using a step motor. A load cell was used to log the applied load on the FSR sensor when a load is applied (Figure 6b). The load tester controls the travel distance using a TB6600 motor driver and an Arduino Uno board (Turin, Italy) (Figure 6c). Figure 6d shows the DAQ circuit using an Arduino Uno board to measure the pressing load of the load cell and the resistance change of the FSR sensor according to the load applied by the load tester. Figure 5: Resistance measured by FSR sensing surface. This is a DAQ circuit using an Arduino Uno board to measure the applied load from the load tester, the pressing load of the load cell, and the resistance change of the FSR Sensor. The FSR sensor load test setup is driven by a stepping motor, with a punch end diameter of 10 mm to match the size of the manufactured sensor, which is 10 \(\times\) 10 mm. The operation is programmed to pressurize in five stages and then decompress in five stages, with a holding time of 30 s per stage. The test was conducted with a movement step in the load application direction of 10 steps (approximately 0.1 mm per step). Initially, a 0.2 mm gap was maintained between the FSR sensor and the force punch using a filler gauge. The 10-step moving distance is 0.1 mm, but the 0.2 mm interval is maintained to avoid damage to the sensor's upper surface due to filler gauge measurement during test setup. Once the setup was completed, the five-stage compression was automatically operated by the program. Data acquisition was performed using an Arduino Mega board equipped with a 10-bit ADC, with a data acquisition rate of 10 Hz. The current graph \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **FSR Sensor Name** & **Average Resistance** & **Comments** \\ \hline
1 & Velsostat & 25.2 k\(\Omega\) & Hand-made sensor \\ \hline
2 & 4B & 37.12 k\(\Omega\) & Hand-made sensor \\ \hline
3 & 9B & 13.7 k\(\Omega\) & Hand-made sensor \\ \hline
4 & TE & 0.27 \(\Omega\) & Hand-made sensor \\ \hline
5 & 9B + silicone sealant & 0.88 M\(\Omega\) & Hand-made sensor \\ \hline
6 & Interlink FSR-402 & 0.2 M\(\Omega\) & Commercial sensor \\ \hline
7 & Flexiforce A201-1 & 1.71 M\(\Omega\) & Commercial sensor \\ \hline
8 & Flexiforce A201-25 & 33.52 M\(\Omega\) & Commercial sensor \\ \hline
9 & Flexiforce A201-100 & 53.1 M\(\Omega\) & Commercial sensor \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of measured resistance between hand-made sensors and commercial FSR sensors (measuring distance: 8 to 9 mm). Figure 6: FSR sensor load test setup. displays data values that represent both numerical data and time. The data interval used for measurement was 1000 ms, meaning one data point was collected every second. Figure 7 shows the output voltage of the Interlink FSR-402 sensor under a load cell load and a 100 \(\Omega\) resistor. After calibration was performed at an initial load of 200 g, the load was gradually increased and decreased from 0 to 4800 gf. To represent the load and output voltage on the same scale, the output values were multiplied by 500 for the graph. The graph demonstrates that the same load increase and decrease pattern and corresponding output waveform can be observed for both loading cycles. The resistance value of the Velostat FSR sensing surface was measured to be approximately 25 k\(\Omega\), so a fixed resistance of 100 \(\Omega\) was used to measure voltage based on the voltage divider principle. To verify the repetition characteristics of the sensor during the continuous compression load test, the test was repeated three times.