A calibrator especially suitable for calibrating electromagnetic flow velocity sensors under field conditions requires no source of water and no source of electrical power. The calibrator includes a pickup coil that intercepts all or a known fraction of the flux generated by the sensor and generates a voltage in response to the flux. The voltage is applied to the electrodes of the sensor thereby simulating a flow velocity. The gain of the sensor is adjusted so that the simulated flow velocity equals a pre-determined reading. The pickup coil may include a number of taps that may selectively be connected to an electrode of the sensor to simulate flow velocities of various magnitudes, thereby permitting the linearity of the sensor to be checked. The calibrator also includes a direct conductive path that may selectively be connected between the electrodes of the sensor to simulate the zero flow velocity condition, thereby permitting the zero offset of the sensor to be checked.