A device for measuring in situ the velocity of fluid flow in a production or injection well in which a packer is inflated between the tool housing and the casing wall, causing the total fluid flow to pass inside the tool and over a spinner. The measurement is made with the tool stationary, after borehole fluids have been pumped to inflate the packer. The packer flowmeter was introduced in the mid-1950s. It is a type of diverter flowmeter, but has generally been replaced by petal basket and inflatable diverter flowmeters.