Sensors for Heart Rate Measurement: Identifying the Correct Example

Heart rate in medical and wearable applications is commonly derived from the heart’s electrical signals (via an keyword electrocardiogram) rather than temperature, mechanical strain, or simple touch contact. An keyword ECG sensor specifically captures these bioelectric signals, enabling estimation of heart rate by detecting characteristic waveform timing (typically the keyword R-peaks in the ECG trace).

In contrast:

• A keyword thermocouple is a keyword temperature measurement device, producing a voltage related to temperature, not heart electrical activity.
• A keyword strain gauge measures deformation/force-induced strain, not cardiac electrical patterns.
• A keyword touch sensor detects contact/pressure events, not the timing of cardiac electrical depolarization.

Therefore, the correct choice for a heart-rate-measuring sensor is (iii) Electrocardiogram sensor.