The QL40-ELOG digital probe measures 8, 16, 32 and 64 inch normal resistivity, single point resistance (SPR) and spontaneous potential (SP) simultaneously. Users can log resistivity profiles with different depths of investigation and gain information about permeability, porosity, water quality and geological formation properties.


  • Bed boundary analysis
  • Facies changes
  • Quantitative geological formation properties
  • Identification of hydrostratigraphic units
  • Aquifer thickness
  • Water quality
  • Identification of hydrocarbon intervals
  • Detection of ore body zones

Operating Conditions

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

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

[_] Required
[X] Not Necessary

Features & Benefits

  • Four resistivity measurements are recorded compared to two offered by most other manufactures
  • Can be combined with other logging tools of the QL product line or operated as a standalone tool
  • With a simple firmware upgrade, the application can be extended to a QL40-IP Induced Polarization probe to record the chargeability of the formations
  • Ultra slimline and easy one-person operation

Specifications – Metric/English

Specification Metric Imperial
Diameter 43 mm 1.7″
Length 1.9 m 74.8″
Weight 9 Kg 19.8 lbs.
Max. Temp. 70ºC 158ºF
Max. Pressure 200 bar 2900 psi


Sensor: Stainless steel electrode
Resistivity Range: 0.1 to 100,000 Ohm-m
Resistivity Accuracy: 1% Full Scale
SPR Range: 0.1 to 100,000 Ohm
SP Range: ± 18 V
SP Accuracy: ± 2.5 mV
SP Resolution: 0.5 mV

QL Stack Possibilities

  • QL40ELOG + QL40GR (Gamma) + QL40MGS (Magnetic Susceptibility): Mining, Exploration
  • QL40ELOG + QL40GR (Gamma) + QL40OBI (Optical Televiewer): Exploration, Bedding Planes, Fractures in Air or Clear Water
  • QL40ELOG + QL40GR (Gamma) + QL40ABI (Acoustic Televiewer): Exploration, Bedding Planes, Fractures in Fluid-filled boreholes
  • QL40GR (Gamma) + QL40ELOG +QL40FTC (Fluid Res, Temp): Hydrogeologist’s Tool, Groundwater exploration and assessment


Data Sheet
User Guide

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