| Factor | Impact Mechanism | Improvement Measures |
|---|---|---|
| Sensor Nonlinearity | Nonlinear relationship between sensor output and physical quantity (e.g., thermocouple nonlinearity at high temps) | • Choose sensors with better linearity (e.g., PT100 over thermocouples) • Apply polynomial software compensation |
| Sensor Aging | Material degradation over time (e.g., platinum wire contamination in RTDs, thermocouple oxidation) | • Regular calibration (annual for industrial use) • Use sealed thin-film sensors (e.g., PT100) |
| Self-Heating | Excitation current causing sensor heating (especially high-resistance RTDs like PT1000) | • Reduce excitation current (<1mA for PT1000) • Use pulsed power supply |
| Interference Type | Typical Manifestation | Solutions |
|---|---|---|
| EMI | Random spikes from VFDs/motors (±50mV noise) | • Use twisted-pair shielded cables (single-point shield grounding) • Keep >30cm from power cables |
| Ground Loop Noise | Common-mode interference from ground potential differences (e.g., 10Hz hum) | • Switch to differential input • Use isolated transmitters (e.g., ADI ADUM1411) |
| Lead Resistance | Voltage drop over long distances (5Ω @100m copper wire) | • 3-wire/4-wire RTD connections • Use current transmission (4-20mA) |
| Design Aspect | Error Source | Optimization Methods |
|---|---|---|
| Voltage Reference Accuracy | Reference drift (±100ppm/°C) | • High-precision references (e.g., MAX6126 ±0.02%) • Add temperature compensation |
| Amplifier Noise | Op-amp input noise (e.g., 10μVp-p) | • Low-noise op-amps (e.g., TI OPA2170, 1.1nV/√Hz) • Bandwidth limiting (LPF) |
| ADC Quantization Error | 12-bit ADC LSB=0.024%FS | • Higher resolution (≥16-bit) • Oversampling + digital filtering |
| Parameter | Accuracy Impact | Countermeasures |
|---|---|---|
| Temperature Drift | Component parameter shifts (±50ppm/°C resistors) | • Low-drift components (±5ppm/°C metal film) • Thermostatic designs (precision instruments) |
| Mechanical Vibration | Contact resistance changes (loose terminals) | • Spring-loaded terminals • Vibration-proof soldering |
| Humidity Corrosion | PCB leakage currents (high-impedance paths) | • Conformal coating • Sealed connectors (IP67) |
graph LR A[Sensor Error ±0.1%] --> B[Transmission Loss ±0.05%] B --> C[Signal Conditioning ±0.03%] C --> D[ADC Conversion ±0.01%] D --> E[Total Error ±0.19%]
Case 1:
Issue: 4-20mA signal ±1.5% error over 300m
Solution: Upgraded to low-impedance twisted pair (24AWG→18AWG) + 250Ω precision resistor, reduced to ±0.2%
Case 2:
Issue: PT100 ±3°C fluctuation in EMI-heavy environment
Solution: 3-wire connection + ADI AD7124-4 built-in digital filtering, stabilized to ±0.5°C
Static Test:
Input known values via calibrator (e.g., Fluke 725), compare measurements
Dynamic Test:
Apply step signal (0→50% range), observe response time/overshoot
Long-Term Stability:
1-month continuous logging, analyze standard deviation (σ)
Sensor linearity <±0.1%FS
Shielded twisted-pair cabling
ADC effective bits ≥16
Temperature-compensated circuitry
Gold-plated connectors
Key Insight: In industrial settings, transmission interference and temperature effects account for most errors. Differential inputs + current transmission resolve 80% of accuracy issues.
