How differential-pressure sensing measures welding gas accurately

One of SUXIN’s headline specs is shielding-gas flow measurement accuracy of 1% FS (full scale). It means that across the entire range, the measured flow deviates from the true flow by no more than one percent of full scale — the bedrock of every “gas saving” and “gas control” action.

To be clear, current is the dominant parameter in welding, and SUXIN measures current to the same 1% FS; this article focuses on differential-pressure measurement of shielding gas because measuring gas accurately across different gas types has long been an industry challenge.

If you cannot measure it, you cannot control it. If the flow measurement itself drifts or distorts, “supply on demand” and “save about 25%” mean nothing; accuracy is what turns waste from a feeling into something quantifiable and controllable.

On the shop floor, welding often switches between pure argon, mixed gas and CO₂ — and that is exactly where sensor selection matters. Thermal measurement depends on the gas’s thermal-conductivity properties — one gas, one calibration; change the gas without recalibrating and it drifts — and because welding changes gases frequently, thermal sensing does not fit. Differential-pressure sensing instead infers flow from the pressure drop across a laminar element, which relates mainly to gas viscosity and is more stable across gases; SUXIN adopts it accordingly, layering on proprietary temperature-pressure compensation and high-frequency sampling to hold 1% FS across the full range.

This accuracy is not just a claim — third-party calibration by the Nanjing Municipal Institute of Metrology Supervision and Testing shows that within 50 L/min (CO₂), most SWISS-200 measurement points carry a maximum indication error of 0.52% and repeatability of 0.02–0.04% FS, traceable to the International System of Units; SWISS-60 also holds a calibration certificate. We state it conservatively as 1% FS externally.

Accurate sensing is only the start — it lets the controller run an active closed loop across the whole welding cycle: a smooth ramp at arc start without overshoot, stable flow to process during the arc, and a clean stop at arc off without spill. The chart below compares passive supply with the active closed loop; the shaded area is exactly the waste removed.

It bears emphasizing that welding gas saving is fundamentally about following the process and eliminating waste, not overdrawing the process by blindly cutting the flow. The job of shielding gas is to keep air out and protect the weld pool; what can be saved is the “outside-the-weld” ineffective supply — overshoot, spill, flow mismatch and leakage — never cutting flow below what the weld needs, which only buys porosity and rework. That is precisely why measuring flow accurately comes first: measure it right, and you can both reclaim the waste and stay inside the process window. For the fuller mechanism of gas saving, see The complete guide to welding gas savings.

SUXIN has long focused on smart welding; its high-precision gas sensing and active closed-loop gas control are deployed on leading lines, backed by 70+ invention patents. Accurate sensing is the shared foundation of welding gas saving, welding process monitoring and welding data acquisition.