2.It adopts three anti-shell design, waterproof, dustproof and shockproof; 3.On-site testing is simple and fast, no need to manually interpret the acoustic parameters, directly display the crack depth; 4.The instrument is easy to operate, fast to master, no need for professional knowledge; 5.High accuracy, the maximum error is not more than 5 mm or 2%-10% of the actual seam depth; 6.Use bracket test without scribing, accurate spacing, adjustable, greatly improving test efficiency.