Abstract: Photoplethysmographic device for measuring a heart rhythm, comprising a housing having a contacting surface and a control unit, a photoplethysmographic sensor mechanically attached to the contacting surface and connected to the control unit, wherein the control unit is arranged to receive a photoplethysmographic signal from the photoplethysmographic sensor, a fastening band having a first end and a second end, the first end and second end attached to the device for attaching the device to a subject with the contacting surface contacting the subject's skin, a pressure sensor attached to the contacting surface in close proximity to the photoplethysmographic sensor. The control unit is arranged determining whether the pressure from the pressure sensor is in a range suitable for photoplethysmographic measurement by the photoplethysmographic sensor.