Whether you use manual grease guns or automatic lubricators, ultrasound needs to be part of your solution for optimizing bearing re-lubrication. You need to decide when a bearing needs new grease, how much grease is required, and whether or not the grease is arriving at its intended destination.
Ultrasound likes to stay within the medium it is created so a direct contact point to the bearing is preferred. But any point in the plant can be audited for lubrication performance. A zirk fitting attached to a grease tube which traces back to the bearing is an ideal spot to place your ultrasound sensor can capture conditional data and ensure grease is flowing freely to the bearing.