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For industrial equipment fault diagnosis, including online monitoring of fans, water pumps, motors, compressors, as well as structural testing, modal analysis, drop tests and other test scenarios, IEPE accelerometers (commonly referred to as ICP piezoelectric sensors in the industry) are the most widely used vibration sensing devices at present.
Compared with traditional charge-output piezoelectric sensors, IEPE sensors integrate impedance conversion integrated circuits inside the sensor housing, eliminating the need for an external charge amplifier. They feature simple two-wire wiring and low output impedance. However, many test engineers frequently encounter issues during practical operation, such as no sensor output, low-frequency signal distortion, insufficient high-frequency response, and signal clipping.
In this session of Vibration Classroom, we provide a comprehensive explanation of IEPE sensors from multiple dimensions: basic principles, internal circuitry, signal characteristics, selection logic, installation and wiring, and fault troubleshooting, to help you avoid common testing pitfalls.
IEPE stands for Integrated Electronics Piezo‑Electric, namely an integrated-circuit piezoelectric sensor. Its core sensitive element is piezoelectric ceramic material, which operates based on the direct piezoelectric effect: when the sensor vibrates along with the measured object and generates acceleration, the piezoelectric crystal receives force from the inertial mass block and internally produces a charge signal proportional to the vibration acceleration.
The direct output of a piezoelectric crystal is a high-impedance charge signal, which is highly susceptible to cable capacitance, ambient humidity and electromagnetic interference and cannot be transmitted over long distances directly. An IEPE sensor integrates a dedicated impedance conversion IC circuit inside its housing to convert the high-impedance charge signal into a low-impedance voltage signal for external output.
✅ Core Advantages of IEPE Sensors:
Low-impedance output (<100Ω): It greatly reduces signal interference caused by cable distributed capacitance and ambient humidity, supports long-distance cable transmission, and adapts to complex factory and outdoor working conditions.
Low drift and high measurement stability: Within the full operating temperature range, the temperature drift of bias voltage and zero drift after impact are controlled within a narrow range, and the baseline is not prone to offset after multiple impacts.
Two-wire shared-line design: Excitation power supply and vibration signals share the same cable set; multiple independent control wires are not required. Ordinary shielded twisted pairs and coaxial cables are both applicable, leading to low wiring costs.
Strong universality: It outputs a standard analog voltage signal. Most vibration acquisition instruments and dynamic signal analyzers on the market come with built-in IEPE constant-current excitation, enabling cross-brand hardware compatibility.
Compact structure and high stiffness: Miniaturized packaging of internal circuits results in a lightweight sensor with a high natural frequency. It is suitable for both small component testing and shock tests.
Simplified system: No separate charge amplifier is required, making the assembly of the complete test system easier.
⚠️ Supplementary Distinction: Charge-output sensors require an external charge amplifier. IEPE sensors cannot be used with charge amplifiers and must adopt constant-current source excitation. The two systems cannot be mixed.
Inside an IEPE sensor, the piezoelectric element is connected in parallel with a capacitor C and leakage resistor R, followed by an impedance conversion circuit centered on a field-effect transistor. When the measured acceleration acts on the piezoelectric element, a charge quantity ΔQ is generated. The open-circuit voltage across the piezoelectric element follows the formula: ΔV = ΔQ / C
The capacitance C of the piezoelectric crystal itself is very small. The original charge signal is an extremely high-impedance signal; minor leakage current in cables or the environment will cause signal attenuation and distortion. After impedance conversion by the built-in IC circuit, the output becomes a low-impedance voltage signal that can be transmitted directly to downstream acquisition equipment.
Signal output form: The IEPE output is a composite signal superimposed by DC bias voltage and AC vibration signal.
Static DC component: Typical bias voltage is 11±2 VDC. After the sensor is powered on and stabilized, this DC voltage can be measured at the output terminal when no vibration exists.
Dynamic AC component: The AC voltage signal generated by measured vibration, superimposed on the DC bias, represents the actual vibration magnitude.
Downstream equipment supports two processing methods:
DC Coupling: Fully retains both bias voltage and AC vibration signals, suitable for low-frequency and ultra-low-frequency vibration testing.
AC Coupling: Filters out the DC component via a blocking capacitor and retains only the AC vibration signal.
Key Knowledge Point: AC coupling forms a high-pass filter and directly cuts off low-frequency components. For ultra-low-frequency infrastructure and foundation vibration testing at the 0.1 Hz level (or lower), AC coupling must be disabled and DC coupling mode adopted.
The voltage sensitivity of an IEPE sensor is directly constrained by its peak measurement range. The peak full‑scale output voltage is generally ±5 V. Conversion formula: Range (peak, g) = 5 V / Sensitivity (V/g)
Example: A high‑sensitivity sensor with 20 V/g sensitivity has a full‑scale range = 5 ÷ 20 = ±0.25 g.
Core conclusion: The higher the sensitivity, the smaller the maximum measurable range.
For faint vibration monitoring of buildings and foundations, high‑sensitivity models are preferred to capture tiny vibration. For equipment shock and high‑vibration working conditions, low‑sensitivity, wide‑range sensors should be selected to prevent signal clipping and saturation distortion when the vibration amplitude exceeds the range.
Note: The rated shock limit of a sensor is a mechanical tolerance index under unpowered conditions and is not equivalent to the measuring range under powered operation. If vibration exceeds the range during powered operation, signal distortion will occur directly.
IEPE sensors are powered by a constant current source instead of an ordinary regulated DC power supply. For regular Xiyuan IEPE sensors, the excitation voltage range is 18 ~ 28 VDC; the common excitation current is 2–10 mA.
Insufficient current: Signal attenuation and waveform distortion under long-cable and high-frequency conditions.
Excessive current: Overheating of the sensor’s internal circuit, increased temperature drift, and in severe cases, shortened device service life.
Standard calibration conditions before delivery (Xiyuan Electronic): 160 Hz, 4 mA constant current excitation, input acceleration of 10 m/s², ambient temperature of 20±5°C. All sensitivity and frequency response specifications are calibrated under these conditions.
● Turn on IEPE constant-current excitation and measure the core wire against the shield using the DC voltage range of a multimeter.
● Normal reading: 9~13 V DC bias voltage; the voltage remains basically stable when no vibration occurs.
● Voltage ≈ 0 V: Circuit board short circuit or constant-current source not activated.
● Voltage obviously outside the 9–13 V range: Cable open circuit or damaged sensor.
● Normal bias voltage but no output: Single-end short circuit.
❌ Mistake 1: Direct connection to a regulated DC power supply without a constant-current source → Burnout of the sensor’s internal integrated circuit
❌ Mistake 2: Connecting a charge amplifier directly to an IEPE sensor → Mismatch and no valid output
❌ Mistake 3: Enabling AC coupling for bridge / building low-frequency testing → Direct loss of low-frequency signals and distorted test data
❌ Mistake 4: Grounding both the sensor end and instrument end of the cable shield simultaneously → Ground loop and severe 50 Hz power-frequency noise
❌ Mistake 5: Plugging and unplugging sensor connectors while powered on → Surge breakdown of the FET chip
❌ Mistake 6: Using low 2 mA excitation current for long cables under high-frequency conditions → High-frequency waveform distortion and amplitude attenuation
When abnormal signals occur, troubleshoot in the following sequence. Most faults are not caused by damage to the sensor itself:
Confirm that the IEPE constant-current excitation of the acquisition instrument is turned on, and the excitation voltage and current meet the sensor specifications.
Measure the sensor output bias voltage: normally stable at 9~13 V.
Bias close to 0 V: Circuit board short circuit or constant-current source not activated.
Very low or zero bias voltage, and the abnormality persists after cable replacement: High probability of internal sensor damage.
Check the coupling mode: DC coupling must be set for low-frequency testing; do not enable AC coupling.
Inspect cables for damage and connectors for water ingress or dampness.
Verify secure installation; check whether magnetic bases or adhesive mounting are loose.
Confirm that the vibration amplitude does not exceed the sensor range to avoid signal saturation and clipping.
Yangzhou Xiyuan Electronic Technology Co.,Ltd.
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Tel: +86 514-82885589
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