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3ACS-LU (Logging tool)

Model id: Robertson Geologging Three Arm Caliper with natural gamma


  • borehole diameter, meassured with three sensors/arms
  • total natural gamma

Purpose: borehole calliper

Description: The three-arm caliper provides a single continuous log of borehole diameter as determined by three mechanically coupled arms in contact with the borehole walls. The standard caliper range can be increased using extension arms supplied with the probe. The caliper is a useful first log to determine the borehole condition before running more costly probes or those containing radioactive sources. Opening and closing of the motor-driven caliper arms is under surface control, allowing the probe to be run into the borehole with the arms retracted. Once opened, at the start of logging, the spring-loaded arms respond to borehole diameter variations as the probe is raised up the borehole. The coupling between the arms means that the resulting log usually represents the minimum diameter in non-circular boreholes. A field calibrator is provided to allow logs to be displayed directly in linear metric or imperial units.

Characteristics: Natural-gamma detector: 50 mm x 25 mm NaI(Tl) scintillation crystal


Vertical resolution:0.010 m
Typical logging speed:5.00 m/min
Maximum pressure:20.0 MPa
Maximum temperature:70℃
Required boreholefluid:
no requirementsNo special requirements with regard to the borehole fluid.
Minimum borehole diameter:0.040 m
Maximum borehole diameter:0.710 m
Centralisation required:yes
Type of datatransfer:
cableData are transferred in real time via a cable.
Required type of logging cable:
4 conductorA logging cable with 4 conductors.
Required cablehead:
GO4Connector according to GO 4 standard (4 conductors).
Implement search on winches with this cable head.
Type of signal:
digitalDigital signal transmission.
Acquisitionsystem (recommended):RG-LU
Length:2.39 m
Maximum diameter:0.038 m
Weight:9.2 kg
Belongs to toolstring:
standaloneA stand alone tool that cannot be integrated in a tool string.
Usage conditons:Commercial usage allowed/welcome.
Additional usage conditions:Logging as service by Lund University

Operator and contact:

Operator:Lund University, Engineering Geology
Contact person:Per-Gunnar Alm
Telephone:+46 462228992
Address: John Ericssons väg 1
223 63 Lund, Sweden

End of I-EDDA database record