A zero-method heat flux sensor  has been tested successfully with acceptable precision. Since the device produces a local discontinuity of heat flow, it is necessary to study its thermal fields during operation. One-dimensional heat flow was simulated by a teledeltos paper. The heat produced by the sensor was simulated by using current injection through a potentiometer. The simulation shows that the equipotential lines are straight, which means that no local perturbation appears in the range of this experiment.