Does the scientist Rob ter Horst not use strange reference devices and methods, strange for a scientist that he uses these devices and methods?

For sleep tracking he used partly a professional polsysomography devices. Then he used the Dreem2 as a reference. For heart rate measurements he uses constantly the Polar H10 chest strap, which is not the most accurate device in every range. Are these the conditions of the manufacturers who give him the devices for testing? We …