Ut Rule Of Thumb

RULE OF THUMB ULTRASONIC To find a Depth , given a reading in a screen or the BPL by approximation: For 70º: D= BPL ÷ 3 For 60º: D=BPL÷ 2 For 45° D= BPL÷ 1.4

On the Half skip area: D

On the full skip area: For 70º: D= 2T-(BPL÷ 3) For 60º: D= 2T-(BPL÷ 2) For 45° D=2T- (BPL÷ 1.4)

D

Root Check Technique: A s much as possible a 60º probe is not use for a root check because even a good root bead will produced a high signal which will be easily mistaken for a root defect. A 70º is a better option because a good root bead will produced only a small echo, which means a root defect that produces a high signal like lack of root penetration will be easily identified. See sketch below.

60º Probe

Signal not reflected Reflected signal More sounds reflected back to the probe produces High signal on the screen.

70º Probe Less signal reflected back to the probe produces small echo on the screen.

RADIOGRAPHY: • The intensity of radiation is inversely proportional to the SFD. Inverse Square Law: I x D = I x D • •

When the distance is doubled increased the exposure time by 4 times. When the distance is reduced to half of its original distance, the exposure time will reduce to ¼ of the its original exposure time. Time x Dist. = Time x Dist.

RADIOGRAPHY: Safe Distance Safe Distance=26 Curies Safe Distance= Ci x 37 x130

7.5

By Approximation Exact formula

Edmundo T. Botor Jr. Senior CSWIP 3.2 No.3147-2 PCN Level 2 No.207763