Introduction
Vacuum sintering furnaces require accurate pressure monitoring to maintain the required process atmosphere.
When selecting a pressure instrument, engineers should distinguish between absolute pressure and gauge pressure.
For vacuum processes, absolute pressure is often the more direct way to describe the actual pressure inside the furnace.
1. Absolute Pressure vs. Gauge Pressure
Absolute pressure is measured relative to a perfect vacuum.
Gauge pressure is measured relative to the surrounding atmospheric pressure.
When the furnace pressure is below atmospheric pressure, gauge pressure becomes negative, while absolute pressure remains positive.
2. Why Absolute Pressure Is Useful
Vacuum process recipes often specify pressure in absolute units such as Pa, mbar, or Torr.
Absolute pressure provides a direct value that can be compared with vacuum process requirements without needing to account for changing atmospheric pressure.
3. Select the Correct Measurement Technology
The required instrument depends on the operating pressure range and accuracy.
For rough and medium vacuum, suitable options may include Pirani gauges, piezoresistive sensors, or capacitance diaphragm gauges.
For accurate pressure control at a specified vacuum range, a capacitance diaphragm gauge may be preferred because its reading is largely independent of gas type.
4. Check the Operating Range
Confirm:
Minimum and maximum absolute pressure
Required control accuracy
Gas composition
Process temperature
Installation location
Calibration requirements
Conclusion
Absolute pressure measurement is often more appropriate for vacuum sintering furnace control because it directly represents the pressure relative to vacuum.
The measurement technology should still be selected according to the actual pressure range and required accuracy.
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