As the use of sensor networks has expanded, the demand for robust detectors able to operate in a variety of environments has grown. We present the sensitivity testing of a micro thermal conductivity detector (μTCD) operating in two different modes. The microfabricated device we have designed and tested is composed of a resistive heating element suspended in a micro-channel, which creates excellent thermal isolation and a high heat transfer coefficient between the element and the fluid. The sensitivity of a μTCD integrated into a micro-gas chromatography (GC) system, can be increased by a factor of 10 simply by switching between operation in constant temperature and constant voltage modes. This result agrees with the analytical models and testing data previously reported for macro systems and devices.