Gauge Pres.
Measures pressure relative to atmospheric pressure (output zero at ambient barometric), reporting positive values for pressures above and (in compound gauges) negative for pressures below atmospheric.
A silicon piezoresistive diaphragm separates the process port from a vented reference port that breathes through a small hydrophobic membrane. Atmospheric pressure cancels on both sides; only excess process pressure deflects the diaphragm. On-chip temperature compensation and ADC produce a calibrated voltage or digital reading in psi, bar, or kPa.
In plain terms
Like a spring scale that reads zero when the room weighs you, then a positive number when you push down — it cancels the constant gravity of barometric pressure.
Why designers use it
- Tyre pressure monitoring — a TPMS sensor reads gauge pressure (28 psi above atmosphere) directly, no barometric offset.
- Hydraulic system control — pump output is naturally referenced to ambient.
- Compressed-air systems — regulators and gauges are calibrated in gauge pressure (psig).
- Accuracy — excludes the daily ±2 % barometric variation that would otherwise introduce error.
Best for
- TPMS
- Hydraulics
- Compressed gas
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- Where altitude or true barometric measurement is needed — pull an absolute pressure sensor.
- In sealed environments where barometric reference can't track ambient — the trapped reference air drifts and the gauge offsets.
Common mistakes
- Sealing the vent port with potting compound — the reference cavity now reads sealed barometric pressure and the sensor reads gauge as if at fixed altitude.
- Mounting the vent port facing upward in a wet environment — water enters the vent and corrodes the diaphragm or creates a drift offset.
Where you will find it
- A Schrader EZ-sensor TPMS module inside a Toyota Camry tyre uses an Infineon SP370 piezoresistive gauge pressure sensor: the chip reads 32 psi above atmospheric continuously and broadcasts via 433 MHz to the dashboard, alerting at any drop below 25 psi gauge.
- A Honeywell ABP DRRD060PG sensor on a TBI Industries compressed-air manifold reads regulated 60 psig: the sensor's I²C output feeds a PLC that throttles the air compressor on/off as pressure droops or peaks.
- A Leemah SP100 hydraulic gauge sensor on a Caterpillar 320 excavator's boom cylinder reads 0–5,000 psig: the gauge reading is what the operator's joystick PWM uses to ramp boom force smoothly without the absolute-pressure sensor's altitude drift.
A short history
A gauge pressure sensor measures relative to the local atmosphere. Think of it like a voltmeter measuring one point relative to another: the reference matters. Gauge pressure is useful when the difference from surrounding air is important, such as measuring liquid level in an open tank.