Introduction: A ceramic pressure sensor core delivers a small differential voltage, so its interface begins with excitation, source impedance, and amplification rather than a ready-made industrial signal.
On a typical electronics bench, the first measurement of such a core often disappoints. A meter set to volts reads almost nothing, the number wanders when a hand moves near the leads, and swapping the probes seems to change the result. The core is usually fine; the instrument is simply not built to look at a few millivolts sitting on top of a common-mode level. Understanding what leaves the core, and why, turns that confusing first reading into a predictable electrical interface that a hardware designer can plan around before committing to a circuit board.
Inside the core, four piezoresistive elements are printed on a ceramic diaphragm and wired as a bridge. With no pressure applied, the bridge sits close to balance, and the voltage difference between its two output nodes is near zero. Pressure deflects the diaphragm, the resistors change by different amounts, and a small voltage difference appears between those nodes. The circuit behind this arrangement is the classic Wheatstone bridge, and the differential output it produces is the entire signal the sensor has to offer. The scale of that signal is what changes the design conversation. Sensitivity is quoted in millivolts per volt of excitation per full scale, written mV/V/FS. The RS186/RS183 core, as one concrete example, is specified at 1.5-3.0 mV/V/FS with a typical value of 2.0 mV/V/FS. Power the bridge with 5 V and the full-scale span lands near 10 mV. That is roughly one hundredth of a volt across the whole 0-1 bar range, so every millivolt of offset or noise is a real fraction of the measurement. Two properties of that output shape every downstream choice. First, the signal is differential: it exists between two output nodes and says nothing on its own about ground. Second, the zero point is not exactly zero. Laser calibration holds the zero near 0 ± 0.4 mV/V, which is tight for a raw core but still meaningful beside a 10 mV full-scale span. Both facts point toward an amplifier that reads the difference between two nodes and rejects whatever voltage they share. It also helps to be clear about what this output is not. A millivolt bridge is not a 4-20 mA current loop, not a 0-10 V analog output, and not an RS485 digital signal. Those formats belong to transmitters and pressure sensor modules that add circuitry, housing, and connectors around the core. Treating the core as a finished industrial output is the most common reason a first prototype behaves unexpectedly.
Excitation is the other half of the interface, and it is easy to underestimate because the supply range looks generous. The same core accepts 2-30 V DC, which suggests almost any rail will do. In practice, the excitation source, the bridge impedance, and the way the amplifier or ADC references its measurement form one loop, and the choices inside that loop set both the signal size and the error budget.
Bridge impedance for this core is about 10 kΩ, high enough that current draw stays modest but low enough that the source still has work to do. At 5 V excitation the bridge pulls roughly 0.5 mA; at 24 V it pulls closer to 2.4 mA. Those currents are small, yet the source has to hold its voltage while supplying them, and any series resistance in wiring, connectors, or a long cable run drops voltage before it reaches the bridge. A source with poor load regulation sags differently at different pressures, because bridge resistance itself shifts slightly with deflection. The same 10 kΩ figure matters at the amplifier input. A high-impedance source paired with a low-impedance load forms a divider, and the resulting gain error stays silent unless it is calculated. This is the practical reason instrumentation amplifiers with high input impedance are the default front end for bridge sensors: they read the differential voltage without pulling meaningful current from the bridge, so the sensitivity quoted in the datasheet survives contact with the circuit.
Because sensitivity is expressed per volt of excitation, the output is ratiometric by nature: raise the excitation and the millivolts rise with it, lower it and they fall. A designer can therefore pick an excitation level that suits the amplifier and ADC, and the 2-30 V DC range leaves plenty of room. What the wide range cannot do is excuse an unstable supply. Any drift, ripple, or thermal change on the excitation line appears directly in the measured signal, scaled by the same mV/V factor that defines the sensitivity. The clean solution is to make the measurement ratiometric end to end. If the ADC uses the excitation voltage as its reference, supply variation divides out of the result, and the reading tracks pressure rather than the power rail. When that is not possible, the excitation source needs its own stability budget, because a fraction of a percent of drift on a 5 V rail is a fraction of a percent of error on a 10 mV span. A quiet, well-referenced excitation usually buys more accuracy than a higher voltage.
Once the signal is understood as a small differential voltage riding on a common-mode level, the front end almost writes itself. An instrumentation amplifier, typically built from three op-amps, offers high input impedance on both inputs, a single resistor to set gain, and common-mode rejection that removes the shared voltage the bridge sits on. The Electronics Tutorials differential amplifier reference covers the underlying subtractor idea, and the TI bridge signal-conditioning note walks through how bridge signals are amplified and trimmed in practice. Gain planning is straightforward arithmetic. A 10 mV full-scale span that has to reach a 2-5 V ADC input calls for a gain in the low hundreds, comfortably within reach of a single instrumentation amplifier stage. Leave headroom for the zero offset, since a laser-trimmed zero of ±0.4 mV/V at 5 V excitation is roughly ±2 mV, and that offset gets amplified along with everything else. Many designs remove the residual offset in firmware after a no-pressure reading at startup instead of adding a trim potentiometer. After the amplifier, a simple low-pass filter handles switching noise, mains pickup, and the PWM hash that often lives on the same board. A differential-input ADC keeps the signal path balanced right up to the conversion, and digital filtering happens after that. Pinout and response time are not part of the published specification for this core, so the first layout should confirm connections against a datasheet before committing to copper. A full PCB design, EMC submission, and calibration procedure sit outside this interface discussion, but the chain itself is well established.
A ceramic pressure sensor core is best understood as a raw bridge: a differential signal of a few millivolts, sitting on a common-mode level, fed from an excitation source that has to stay steady, and sourced through roughly 10 kΩ of bridge impedance. Once that picture is clear, the instrumentation amplifier, gain stage, filter, and ADC stop being arbitrary choices and become consequences of the signal itself. Anyone comparing flush diaphragm ceramic sensor options should check sensitivity, bridge impedance, excitation range, and zero tolerance first, because those four numbers decide how much conditioning work the interface needs.
A: It means the full-scale signal is expressed as a fraction of the excitation voltage rather than as a fixed voltage. A core rated at 2.0 mV/V/FS produces about 10 mV at full scale when excited with 5 V, and about 20 mV at 10 V. The spec describes a raw bridge, so the actual span always depends on the excitation supplied.
A: About 10 kΩ of bridge impedance means the sensor behaves as a high-impedance source. An amplifier with low input impedance loads that source, forms a divider, and quietly reduces the signal before gain is applied. High input impedance also keeps the excitation current stable and limits loading errors, which is why instrumentation amplifiers suit bridge front ends so well.
A: Sometimes, when the ADC has a true differential input, high input impedance, an internal programmable gain amplifier, and enough resolution to see a 10 mV span with useful accuracy. Even then, offset, common-mode range, and noise usually push the design toward an instrumentation amplifier and a simple filter. Treating the core as an ADC-ready source is the exception, not the default.
Wheatstone Bridge Circuit and its Theory of Null Balance Operation
Differential Amplifier Configuration is a Voltage Subtractor Circuit
Texas Instruments - Signal Conditioning for Resistive Bridge Sensors
1bar High-Accuracy Flush Diaphragm Piezoresistive Ceramic Pressure Sensor
