When we designed Arc, we had a few guiding principles in mind. First, we wanted our back injury risk detection and notification solution to be low cost. We understand that companies can often not justify spending big bucks on safety technology, so we wanted to do what we could to lessen the burden. Next we focused on ease of use. We chose the device design and placement to make it simple and easy to pick up the device, put it on, and go on with your day. Wearing a safety solution shouldn’t be a process and it shouldn’t take away from the work to be done.
In this design, there were trade-offs. We decided to sacrifice an acceptable amount of accuracy in order to achieve these goals. Arc will never match an exoskeleton suit with 10 different sensors in terms of complete motion tracking, but we won’t break the bank like one either. We also don’t force customers to buy harnesses, straps, or other accessories. Arc can be worn with nearly any type of clothing and in any environment, put on in seconds, and returned in seconds.
However in our deployments, we have seen some circumstances that result in better data than others. To help, we put together a useful guide for reducing false positives.
Reduce false positives with Arc Devices
Put on the device prior to calibration
This doesn't happen often, but we do see users calibrate the device while on the charging dock (vertical) or while it is in their hand (horizontal) when the typical orientation of the device once it is on the back is somewhere in between. This can lessen or increase the amount of movement needed to track risky motions and postures. To ensure accuracy, make sure the device is on your back when calibration happens.
Properly align the device with the spine
We wanted to put the device on the collar for ease of use and comfort, but occasionally it can be hard to tell whether or not the device is straight. It can be helpful to have another person there to confirm. The device sitting at an angle will cause vibration to go off at unusual times.
Stand with natural, yet proper, posture during calibration
Even if the device is being worn during calibration and it is on straight, one possibility is that during calibration the user is making a point to stand as straight as possible. This is a good thing, but could cause issues if their natural posture isn't as good on the floor.
If, for example, the device is calibrated to 0 degrees and their standard posture on the floor is to slouch and lean over at 20 degrees, then that's 20 fewer degrees of motion they can move before the device buzzes. The optimal solution here (and one that the device trains towards) is to have better posture while out on the floor.
Otherwise, we'll want to have the user stand as naturally as possible during calibration. This isn't as optimal safety-wise, but will cause less vibration and perceived false positives.
Wear optimal clothing that places the Arc device at the base of the neck
Loose clothing may cause the device to "flop" around occasionally. This would probably be most noticeable for twisting or lateral motions. The best way to combat this is heavier or more form fitting clothing that will move less or to wear multiple layers. We usually see the highest accuracy when the device is clipped to the first layer of clothing and is held in place by an additional layer. We know this may not be suitable for all environments though.
Sometimes, users may inadvertently clip the device higher on the neck than desirable. This would be when this user gets the magnetic portion of the clip just past the collar and clips the device, causing most of the device is sticking out above the collar. This can cause two things to happen. First, the device is more likely to "flop" around. Second, the device tracks the motion of the neck rather than the back.
High collared shirts may also situate the devices where it tracks neck motion as well.
The proper location for the device is at the base of the neck. The device should be top for the flexible clip’s loop should be touching the fabric of the shirt collar, or placed as near as possible to it.