A re-wearable physiological monitoring device includes a reusable component and a disposable component. The reusable component includes an electronics module and a latching system for latching the reusable component to the disposable component. The disposable component includes an adhesive patch to be adhered to a user's skin, two electrodes to receive electrical signals from the user's skin, a cradle for the reusable component to be latched on, and a battery to power the device. The disposable component may include a “battery disconnect switch” for disconnecting the battery when the reusable component is not latched on; a gasket for isolating each contact between the reusable component and the disposable component in a waterproof enclosure; and a printed contact within the disposable component that is resistant to scratching. A latching system for the device may include two snap fasteners, alignment feet for keeping the reusable component aligned with the disposable component, and an asymmetrical wall to prevent the reusable component from being placed on the disposable component in the wrong orientation. A method of assembling the reusable component by ultrasonic welding is also disclosed.