Monitoring an injection process

An electronic module adapted to be detachably attached to an injection device for monitoring an injection process performed by means of the-injection device, the injection device comprising:

• feedback means that produce a number of successive mechanical feedback events proportionate to a dose of drug being expelled from the injection device,
• wherein the electronic module comprises:
• an orientation sensor adapted to measure an azimuth angle of an axis of the injection device and vibrational movement of the injection device in a plane perpendicular to the direction of gravity when the electronic module is attached to the injection device, wherein the orientation sensor prepares an azimuth angle signal output at a sampling rate of less than 2 kHz;
• and
• a processing unit configured to receive the azimuth angle signal output by the orientation sensor and identify a dosage unit expelling event based on the signal output and also on the measured vibrational movement of the injection device in a plane perpendicular to the direction of gravity and wherein the processing unit is further configured to count the number of dosage unit expelling events to determine an expelled dose.