Precision Sensor Interface Solution

The Precision Sensor Interface Solution supports a wide range of sensor types including: Strain gauges and load cells for force/weight measurement

Thermocouples (J, K, T, E, N, S, R, B types) for temperature

RTDs (Pt100, Pt1000) for precision temperature

Pressure sensors (piezoresistive, capacitive)

Accelerometers and vibration sensors

and Custom bridge-type sensors. The programmable gain and flexible architecture accommodate sensors with output ranges from microvolts to volts.

Select sensor type based on measurement requirements. Contact our FAE team for sensor-specific interface recommendations.

Ratiometric measurement uses the sensor excitation voltage as the ADC reference voltage. Since both sensor output and ADC reference change proportionally with excitation variations, the ratio remains constant. This eliminates errors from excitation voltage drift caused by temperature or loading. For example, if excitation drops by 1%, both sensor output and ADC reference drop by 1%, resulting in zero measurement error. Without ratiometric measurement, a 1% excitation change could cause 1% measurement error.

Always use ratiometric measurement for bridge sensors. Connect excitation voltage to ADC reference input through appropriate divider.

CMRR (Common-Mode Rejection Ratio) is critical for differential sensors like strain gauges and thermocouples. These sensors often operate in noisy environments where both signal lines pick up common-mode noise. High CMRR (>120dB) means the amplifier rejects common-mode noise by a factor of 1,000,000:1. For example, 1V of common-mode noise would produce only 1μV of output error. Without high CMRR, electrical noise from motors, switching power supplies, and radio sources can overwhelm small sensor signals.

Use instrumentation amplifiers or precision op-amps with high CMRR for differential sensors. Match source impedances for best CMRR performance.

Cold junction compensation requires measuring the temperature at the thermocouple connection point and adding the equivalent thermocouple voltage for that temperature. Implementation steps: 1) Mount a temperature sensor (thermistor, RTD, or IC sensor) near the thermocouple connection terminals

2) Measure cold junction temperature with high accuracy

3) Calculate equivalent thermocouple voltage using standard tables or polynomial

4) Add cold junction voltage to measured thermocouple voltage

5) Convert total voltage to temperature using thermocouple characteristics. The reference design includes integrated cold junction compensation with ±0.5°C accuracy.

Use integrated cold junction compensation from reference design. Ensure temperature sensor is thermally coupled to connection terminals.

Proper grounding and shielding are essential for noise immunity: 1) Use shielded twisted pair cables for sensor connections

2) Connect cable shield at receiver end only (single-point ground)

3) Use differential signaling for long cable runs

4) Implement star grounding with separate analog and digital ground planes

5) Connect ground planes at single point near ADC

6) Use guard rings around high-impedance inputs

7) Keep analog traces away from digital signals

8) Use ferrite beads on power lines for high-frequency filtering. These practices can reduce noise pickup by 40-60dB.

Follow grounding and shielding guidelines from reference design. Use shielded cables for all sensor connections in industrial environments.