Why is the light on Smart Sock 3 purple instead of red?

You may have noticed that the new Smart Sock 3 looks like it has a purple light instead of the red light you may be used to seeing with pulse-oximeters. The Smart Sock 3 continues to use red and infrared lights to estimate your infant’s heart rate and oxygen values (described in the post that can be found here). We added a blue LED light to help us better determine if the Sock is placed correctly on the foot. This blue light, combined with the red light used for pulse-oximetry, gives the Sock Sensor this new purple color. The combination of these LEDs is new technology (patent pending) we’ve developed to help parents better care for their little ones.

How does it work?

During normal Sock operation, we shine red, infrared and blue lights. We then measure how much of each light is received on the other side of the Sock. Because tissue absorbs different colors of light differently, we can use these differences to determine if the Sock is placed securely on your child's foot. This new technology helps us ensure we don’t generate readings when we shouldn’t.

Why is this necessary?

Most pulse-oximeters work under the assumption that they are placed correctly and on a foot, finger, or wrist. If they are not placed on anything, they often have a rigid shape that shines the light directly across that gives an indication that the device is not being worn. This was how Smart Sock 2 worked. With Smart Sock 3 we made a more flexible Sock for better comfort and fit. Because of this new design, we are unable to identify that the light is not coming through the foot in every situation. However, with this new technology in the Smart Sock 3, we are better able to detect when a Sock is not worn correctly. This makes us better equipped to provide the information you desire to help you keep your baby well.