ED-400 PORTABLE EDDY CURRENT UNIT
EQUIPMENT SPECIFICATION ES-101
1.0 Description
1.1 The Model ED-400 is an eddy current
test device, which will locate surface and near-surface discontinuities in
magnetic materials. Nonmagnetic metals
may also be inspected for many types of defects. In magnetic steel products, cracks as small a 0.005 deep may be
detected with ease, when open and normal to the surface.
1.2 The ED-400 instrument utilizes the eddy
current principle, wherein the induced currents in the test part are affected
by changes in homogeneity and uniformity.
Variations in material conductivity, permeability, and thickness are
ignored because of the special design features incorporated in the system. Discontinuities such as cracks, laps, or
seams will disrupt the eddy current pattern induced in the material, and cause
localized magnetic field changes near the probe, which unbalance the instrument
and create meter deflections.
1.3 Initially, the Balance Controls are
adjusted with the probe in air to zero the meter. As the probe is then scanned across the test object, discontinuities
will be indicated as changes in the reading. The Gain Control is adjusted to give the
desired amount of deflection for the defects to
be located. An Alarm Set Control may be
adjusted to activate the threshold audio annunciator for a given meter deflection.
1.4 The state-of-art ED-400 is virtually
insensitive to the background magnetic permeability changes. Thus, no lift-off adjustments are required
when searching for defects through rust, oxide scale, paint and other coatings. Slight rocking of the probe during testing
does not seriously affect the meter reading.
The differential probe forms two legs of a bridge circuit contained
within the instrument.
2.0 Mechanical and Construction
2.1 Dimensions: Hand Held
Unit - 3.5 (8.9 cm) x 7.1 (18 cm) x 1.9 (4.8 cm) high
Carrying Case - 12 (30.5 cm) x 8
(20.3 cm) x 3.5 (8.9 cm) high
2.2 Weight: Overall (unit
with carrying case) - 2.2 lb (1 kg)
Hand Held Unit with Probe - .8 lb (1.8 kg)
2.3 Meter: 2.5 (6.4 cm). The scale is numbered from 0 to 500 in 50
divisions.
2.4 The instrument is housed in
a lightweight, impact resistant case.
The carrying case is designed to protect the unit and accessories during
shipping and when not in use. The foam cutouts
are for the units itself, probe, test block, adjustment screwdriver and
operating manual.
3.0 Electrical and Performance
3.1 The instrument is solid-state construction throughout and
utilizes integrated circuits.
3.2 Frequency: 100 KHz, fixed.
3.3 Power Requirements: Batteries - Two AA alkaline cells only. DO NOT use nickel cadmium cells, as the
voltage is too low. The new
rechargeable alkaline cells are approved for use in this instrument.
3.4 Probes are
interchangeable. Coarse Balance
adjustments are simple for the operator to perform and are outlined in the
operation manual.
3.5 Meter indicates probe unbalance
as it passes over a flaw. Instrument
shows full-scale deflection for 0.008 (20.3 mm) deep mill slot in machined
magnetic material (Steel Test Block, P/N
220004).
4.0 Operation
4.1 The Gain Control determines the sensitivity level and, therefore, the
meter deflection for a given depth of defect.
4.2 The Balance Controls null the meter in air and are used in conjunction
with one another.
4.3 The Power Switch provides
power to the instrument. The
square-faced LED will light when the batteries need to be replaced.
4.4 The Alarm Set is a
continuously variable screwdriver control that adjusts threshold firing point
as a function of meter deflection.
4.5 The Alarm provides an audio indication when meter deflection triggers
the threshold circuit.
4.6 The Probe Connector is a miniature 4 pin screw-on for attachment of
test probes.
5.0 Order Reference
5.1 Model ED-400 Portable Eddy Current
Instrument, P/N 220000, in plastic carrying
case, including steel test block, adjustment screwdriver, standard probe, and 2
AA batteries (installed in the unit).
5.2 Standard Accessories
5.2.1 Battery
(two required to operate instrument), P/N
517760
5.2.2
Standard Crack Detection Probe, 7/16 (1.1 cm) diameter x 1.5 (3.8 cm)
long, 60 (1.5 m) long cable attached,
P/N 220072
5.2.3 Carrying Case, P/N 220003
5.2.4 Steel Test Block, 3.125 (7.9 cm) long x 1.375 (3.5 cm) wide x
.125 (.3 cm) high, P/N 220004
5.2.5 Screwdriver for adjustment of coarse balance and alarm controls, P/N 519929
5.3 Addendum Accessories
5.3.1 Bolt
Hole Probe for 5/16 (.8 cm) to 3/8 (.9 cm) hole, approximately 4 (10.2 cm)
long, P/N 208294
5.3.2 Bolt
Hole Probe for 3/8 (.9 cm) to 1/2 (1.3 cm) hole, approximately 4 (10.2 cm)
long, P/N 208331
5.3.3 Bolt
Hole Probe for 1/2 (1.3 cm) to 5/8 (1.6 cm) hole, approximately 5 (12.7 cm)
long, P/N 208329
5.3.4 Bolt Hole Probe for 5/8 (1.6 cm) to 3/4 (1.9 cm) hole, approximately
5 (12.7 cm) long, P/N 208330
5.3.5 Bolt Hole Probe for 3/4 (1.9 cm) to 1 (2.5 cm) hole
approximately 6 (15.2 cm) long, P/N
208290
5.3.6 Pancake
Probe, 5/16 (.8 cm) high, 6 (15.2 cm) long with attached cable, P/N 220082
5.3.7 Mini-Swivel
Probe, 1/4 (.6 cm) tip diameter, 9.25 (23.5 cm) long (cable required), P/N 220079
5.3.8 Swivel Probe, 3/8 (.8 cm) tip diameter, 12 (30.5 cm) long with
attached cable, P/N 209005
5.3.9 Spherical
Probe, 5/16 (.8 cm) diameter, 1.5 (3.8 cm) long with attached cable, P/N 220085
5.3.10 Wedge Probe, 5/16 (.8 cm) diameter, 1.75 (4.4 cm)
long with attached cable, P/N 209400
5.3.11 Encircling Coil, 1 (2.5 cm) ID, 3 (7.6 cm) square, cable
required, P/N 220084
5.3.12 Probe Cable, 60 (1.5 m) long, P/N
220083
Additional probes and coils may be designed to meet
customers requirements. Contact
factory with desired specifications.
6.0 References
6.1 Instruction Manual, Form No. 19962A, effective Feb. 1, 1995
6.2 Technical paper A Solution to the Permeability and Lift-Off Problems
in Electromagnetic Flaw Detection by R.H. Kenton (1970)
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