Applicable Conditions - JRC Handy Search NJJ-95B Instruction Manual

Velocity V of electromagnetic waves in concrete is obtained from the following formula:
Ｖ＝
C: Velocity of electromagnetic waves in vacuum (in air) (3 × 10
Distance D to the reflecting object is obtained from the following formula:
Ｄ＝

5.2 Applicable Conditions

(1) Applicable measuring conditions
(Waves reflected by objects to be scan tested in reinforced concrete structures must be received
adequately, so the applicable measuring conditions vary slightly depending on the on-site condition.)
○ Scan test depth (covering depth) within 0.5 ~ 30 cm (case where relative permittivity of concrete
is 6.2 and the diameter of the rebar is at least 6mm)
○ Objects to be probed that are at a depth of less than 75 mm have an interval spacing of at least
75 mm and where the depth of the object to be probed is greater than 75 mm, the interval
spacing of the objects is more than the depth
○ Quality of concrete: Uniform
○ Direction of reinforcing steel: Orthogonal to the Handy Search's traveling direction
(2) Inapplicable measuring conditions
○ Scanning of reinforcing steel or the like in concrete whose surface contains objects such as
metal that reflect radio waves
○ Presence of reinforcing steel bars that are parallel to the Handy Search's traveling direction
○ Concrete that has a narrow (pitch) arrangement for the interval of rebar in the horizontal
direction
(Target: depth less than 75 mm → interval between rebar, less than 75 mm
Depth of greater than 75 mm → interval of rebar less than depth)
Ｃ
（ｍ／ｓ）
ε
ｒ
: Relative dielectric constant of concrete (6 to 11 in the example)
１
ＶＴ （ｍ）
２
- 83 -
8
m/s)