The question then becomes 'does sensor [capacity] equate with other gear and augmentation [capacity]'?
"Helmets have Capacity 6 for being tricked out with accessories like trod nets and vision enhancements." P. 438
So can you stick a sensor array capacity [6] into a helmet capacity 6? Well, as an array, it would be considered an AV device, capping it at rating 2. That's ¥2000 for 8 functions including ultrasound. This is way cheaper than using standard AV mods to a helmet. The drawback is that the array is still capped at rating 2, which is the device rating which dictates the device limit which dictates your perception limit.