• Instrument: Hydrocell Hydrogen Generator
• Operating mode: Constant Current (CC), stepped setpoints
• Run duration: 1 minute per measurement
• Recorded parameters: Voltage (V), Current (A), Gas volume collected in 1 minute (mL = mL/min)
• Environment: Ambient lab conditions

1) Repeatability at constant-current setpoints (mean ± SD; %CV)

Flow rate values are expressed in mL/min.

• 1.01 A (n = 3): 11.5, 11.5, 11.0 → 11.33 ± 0.29 mL/min, CV ≈ 2.55%
• 2.01 A (n = 2): 22.5, 22.0 → 22.25 ± 0.35 mL/min, CV ≈ 1.59%
• 3.01 A (n = 3): 33.0, 33.0, 33.0 → 33.00 ± 0.00 mL/min, CV = 0%
• 4.03 A (n = 3): 44.0, 44.0, 44.0 → 44.00 ± 0.00 mL/min, CV = 0%
• ≈5.05 A (n = 3): 55.0, 55.0, 55.0 → 55.00 ± 0.00 mL/min, CV = 0%

2) Flow rate increases predictably with current (calibration behavior)

As the constant-current setpoint increases from ~1 A to ~5 A, the measured hydrogen flow rate increases from ~11 mL/min to ~55 mL/min. The relationship between current and flow rate is strongly linear across the tested range, which supports use of this dataset as a practical calibration curve for estimating hydrogen output from the operating current.

3) Voltage varies slightly at fixed current (expected in CC mode)

At a fixed current setpoint, the operating voltage shows small variations between runs. This behavior is expected in constant-current operation because the power supply adjusts voltage to maintain the set current while the electrolytic cell resistance changes slightly with temperature, electrolyte condition, and gas evolution.

4) Output range demonstrated in this study

Under the tested conditions and 1-minute collection interval, the Hydrocell system produced stable hydrogen output in the range of approximately 11–55 mL/min.