In this paper we propose a feedback architecture with a thermosensitive sensor, based on the thermal Σ-Δ principle to realize digital measurement of physical quantities that interacts with the sensor: temperature, thermal radiation, fluid speed. This architecture uses a 1-bit Σ-Δ modulator for which a considerable part of the conversion functions is performed by a thermosensitive sensor. The sensor is modelled using the electrical equivalence principle and the constant temperature measurement method is applied. We present an analysis of the system performance, in terms of frequency response and system measurement resolution, of a 1-bit first-order Σ-Δ thermal modulator. It is shown that the system performance depends on the system oversampling ratio (OSR) and on the system transfer function pole and zero, which in turn, depends on the thermal and physical sensor characteristics and on the system operating conditions. This system is proposed as anemometer.