A nematic device with a shallow grating and homeotropic anchoring is used to probe the flexoelectric effect. Applying a sinusoidally varying voltage across the cell, the transmittance of the device between crossed polarisers is found to consist of a mixture of 1st and 2nd harmonics, corresponding to the flexoelectric and dielectric responses of the director to the applied electric field. The results are compared with theoretical ones generated using a 1-dimensional approximation to the cell structure, and a value for the sum of the flexoelectric coefficients determined.