Caliper Borehole Logging Probe with Optical Televiewer data
QL40-CAL Tool Bitmap


The QL40-CAL Caliper probe records a single continuous borehole diameter log by means of three mechanically coupled arms in contact with the borehole wall. The 3 arm caliper measurement is a useful first log to determine the borehole condition before running other well logging probes.


  • Borehole diameter measurement
  • Borehole volume calculation before borehole completion, cementation
  • Fracture and cavity localization
  • Rock integrity evaluation
  • Often used in the implementation of environmental correction equations for other logs

Operating Conditions

Borehole Fluid
[X] Water
[X] Mud
[X] Dry

[X] Uncased
[X] PVC Borehole
[X] Steel

[_] Required
[X] Not Necessary

Features & Benefits

  • Calibrated measurement of borehole diameter in inches, centimeters, or millimeters
  • Can be combined with other well logging tools of the QL product line or operated as a standalone tool
  • Operates on any standard wireline (mono, 4 or 7 conductor, coax)
  • Easy exchangeable caliper arm lengths and wear tips

Specifications – Metric/English

Specification Metric Imperial
Diameter 42 mm 1.7 inches
Length 1.78 m 70.3 inches
Weight 10 kg 22 lbs.
Max. Temp. 70ºC 158ºF
Max. Pressure 200 bar 2900 psi


Sensor: Micro-processer controlled potentiometer
Standard Arms: 50 to 406 mm/ 2 to 16 inch borehole diameter
Extended Arms: up to 736 mm/ up to 29 inch borehole diameter
Accuracy: 1 mm
Resolution: 0.5 mm

QL Stack Possibilities

  • QL40CAL + QL40GR (Gamma) + QL40MGS (Magnetic Susceptibility): Mining, Exploration
  • QL40CAL + QL40GR (Gamma) + QL40OBI (Optical Televiewer): Exploration, Bedding Planes, Fractures
  • QL40CAL + QL40GR (Gamma) + QL40ABI (Acoustic Televiewer): Exploration, Bedding Planes, Fractures
  • QL40CAL + QL40GR (Gamma) + QL40RES (Resistivity)+ QL40FTC (Fluid Res, Temp): Hydrogeologist’s Tool, Groundwater exploration and assessment


Data Sheet
User Guide

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