Need for Signal Conditioning

Sensor outputs are usually small (mV), noisy, non-linear, or at levels the ADC cannot accept directly. Signal conditioning converts them into a clean signal that matches the ADC input range.

Needs

1. Weak signals must be amplified.
2. Noise and interference must be removed.
3. Protection from high voltages and ground loops.
4. Sensor non-linearity must be corrected.
5. Match ADC input range and impedance.

Amplification

Increases signal level, e.g. thermocouple mV to 0-5 V. An instrumentation amplifier is preferred for bridges because of high input impedance and high CMRR. Gain: $G = 1 + 2R_f/R_g$ (3 op-amp in-amp).

Attenuation

Reduces large signals to the ADC range, using a resistor divider: $V_{out}= V_{in}\,R_2/(R_1+R_2)$.

Isolation

Electrically separates the sensor side from the DAQ side using optocouplers, transformers or isolation amplifiers. It prevents ground loops, protects the patient and equipment, and rejects common-mode voltage.

Linearization

Corrects a non-linear sensor response (thermistor, thermocouple) using analog circuits, look-up tables or polynomial equations in software, so output is proportional to the measured quantity.

Function	Purpose
Amplification	Raise small signals
Attenuation	Bring large signals into range
Isolation	Safety, no ground loops
Linearization	Proportional output

Exam tip

Mention the in-amp for amplification, optocoupler for isolation and look-up table for linearization.