The Portable Electronic Divided Bar (PEDB) is an invaluable tool for measuring the thermal properties of rocks for geothermal 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 require AC power and (usually) a source of running water to cool the pump motors. In contrast, the PEDB maintains the temperature differential to a high stability and precision using electronic Peltier devices, which heat or cool in rapid response to an applied electric current. The PEDB runs on 12-volt DC power (AC converter included) and 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 has the major advantage that it can 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.

Hot Dry Rocks is currently updating the PEDB to a fully digital version. The new model will improve stability, precision and serviceability, as well as allowing new functionality. We anticipate that the new PEDB model will be capable of direct thermal diffusivity measurements, in addition to the current capability for thermal conductivity and specific heat capacity.

Features and Specifications

  • 12-volt power supply, with AC converter

  • Temperature at hot and cold plates kept stable to within ±0.02°C

  • Temperature differential adjustable to 10°C, 15°C or 20°C

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

  • Achievable thermal conductivity accuracy ±2%

  • Heat capacity to ±1% as described in DOI 10.1520/GTJ20130168

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

  • Replaceable contact plates (in case of damage)

  • Swivel head to accommodate samples with non-parallel surfaces

  • Simple controls

  • Dimensions: approx 26 cm wide, 28 cm deep, 28 cm high

  • Weight: approx 8 kg

  • Data logged to PC

Prototype of the fully digital, portable electronic divided bar

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

© 2018 by Hot Dry Rocks Pty Ltd.