R-4 Magnetic Reed Switch Probe – Extensometer / Settlement

The R-4 is used to manually measure settlement or heave of soils at various depths, which allows producing a settlement/heave profile.

Description

The R-4 magnetic probe extensometer consists of an array of magnetic targets, surrounding a common access pipe, positioned at different depths along the length of a borehole or the height of an embankment or fill.

A reed switch probe, lowered down the access pipe, detects the position of the magnet anchors outside the tube. The probe is suspended by a single graduated tape that incorporates the electrical leads. The tape graduation is used to determine the deformation between magnetic anchor points along the pipe’s axis.

The magnetic anchors are available in two configurations: leaf spring anchor, for borehole installation, and plate anchor, for embankment or fill installation. The leaf spring anchor can be pushed in place or lowered with the access pipe and released with an external draw wire.

The plate anchor consists of a plate with a central hole. The plate anchors are installed with the access pipe as the construction of the embankment or fill proceeds. Telescoping access pipes are used where deformations exceeding 1% are expected. The R-4 system is compatible with standard inclinometer casings. The use of a probe centralizer is recommended for repeatable readings.

SPECIFICATIONS
R-4 READOUT UNIT (probe, reed switch, cable and reel)
Model No. FR-R4-30M FR-R4-50M FR-R4-100M FR-R4-150M FR-R4-100F FR-R4-300F
Probe diameter 16 mm 16 mm 16 mm 16 mm 16 mm 16 mm
Probe length 230 mm 230 mm 230 mm 230 mm 230 mm 230 mm
Tape length 30 m 50 m 100 m 150 m 100 ft 300 ft
Graduation 1 mm 1 mm 1 mm 1 mm 0.01 ft 0.01 ft
PVC COLLAR TAPE GUIDE 
Model No. Required pipe diam.
10-1131001072 33 mm    
20-11312067 48 mm    
20-1131002065 70 mm    
20-1131002064 85 mm    
PUSH-IN LEAF SPRING ANCHOR 
Model No. Min. bore diameter O.D.  Anchor ext. Pipe  diameter
FR-1131A50400 76 mm 140 mm 33 mm
FR-1131A50400C 101 mm 152 mm 48 mm
FR-1131A50400A 127 mm 254 mm 70 mm
FR-1131A50400B 152 mm 254 mm 85 mm
LEAF SPRING ANCHOR  
Model No. Min. bore diameter O.D.  Anchor ext. Pipe  diameter
FR-1131A50100 76 mm 222 mm 33 mm
FR-1131A50100C 101 mm 254 mm 48 mm
FR-1131A50100A 127 mm 279 mm 70 mm
FR-1131A50100B 152 mm 305 mm 85 mm
MAGNETIC PLATE ANCHOR 
Model No. Pipe diameter
FR-1131A50200 33 mm
FR-1131A50200C 48 mm
FR-1131A50200A 70 mm
FR-1131A50200B 85 mm
MAGNETIC DATUM RING ANCHOR 
Model No. Pipe diameter
FR-1131A50300 33 mm
FR-1131A50300C 48 mm
FR-1131A50300A 70 mm
FR-1131A50300B 85 mm
ACCESS PIPE 
Model No. Length O.D.
99-PLAST100CSG8005 1.5 or 3 m 33 mm  
99-PLAST150CSG8005 1.5 or 3 m 48 mm
TELESCOPING ACCESS PIPE 
Model No. O.D. I.D. Length
20-1131002004 33 mm 24 mm 1.5, 2.0 or 3.0 m
20-1131002059 48 mm 38 mm 1.5, 2.0 or 3.0 m
TELESCOPING COUPLING  
Model No. O.D. Total Range  
20-1131002043 42 mm 152 mm  
20-1131002060 57 mm 152 mm  
INSTALLATION JIG FOR TELESCOPING ACCESS PIPE 
Model No. O.D.    
40-1131042900 33 mm    
40-1131043000 48 mm    
END CAP
Model Pipe diameter
05-35019 33 mm    
05-35021 48 mm