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The Portable Electronic Divided Bar (PEDB) is an invaluable tool for measuring the thermal properties of rocks for geotechnical evaluation or resource exploration.

How a divided bar works

A divided bar applies a known temperature differential across a rock sample in series with a material of known thermal properties. A conventional divided bar maintains the temperature differential using thermostatically controlled water baths. These baths are bulky and (usually) require a source of running water to cool the pump motors. In contrast, the PEDB maintains the temperature differential at ± 0.01°C with high stability using electronic Peltier devices, which heat or cool in rapid response to an applied electric current. The PEDB requires no external cooling.

The thermal conductivity of a rock sample is measured using any divided bar by determining the ratio between the thermal gradient across the rock and that across the known material under steady-state conditions.  The PEDB can also be used in a ‘transient’ mode to measure volumetric heat capacity by determining the amount of heat absorbed by the rock sample as it warms (or cools) from one steady-state temperature to another.


Features and Specifications

  • Inbuilt power supply, with AC cable

  • Temperature at hot and cold plates kept stable to within ±0.01°C

  • Independent, real time control of hot and cold plate temperatures

  • Designed for a thermal conductivity range 0.5 – 12 W/mK

  • Thermal conductivity accuracy typically ±2%

  • Heat capacity to ±3% as described in DOI 10.1520/GTJ20130168

  • Accepts samples of arbitrary shape up to 65 mm maximum width

  • Modular construction for easy service and repairs

  • Swivel head to accommodate samples with non-parallel surfaces

  • Simple controls

  • Dimensions: approx 27 cm wide, 31 cm deep, 47 cm high

  • Weight: approx 12 kg

  • Controlled directly from PC (PC not included)

In 2020, Hot Dry Rocks released a fully digital PEDB. The new 'Mark II' model has improved stability, precision and serviceability compared to the original, as well as allowing new functionality. We anticipate that the PEDB Mk II will be capable of direct thermal diffusivity measurements, in addition to the current capability for thermal conductivity and specific heat capacity.


Fully digital, Mark II portable electronic divided bar

For additional information or a quotation for a PEDB, please contact us directly

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