DVD-2800 Ultra High-Temperature Vertical Dilatometer

The DVD-2800 is a fully automated dilatometer system designed to measure dimensional changes of a specimen brought about by changes in its thermal environment. Linear thermal expansion coefficient, shrinkage attendant to sintering, phase transformations, annealing characteristics and other physical or chemical changes manifesting themselves in a change of a linear dimension can be precisely determined at temperatures up to 2800°C. Processing parameters can be studied in great detail through duplication of actual thermal cycles and rates. Due to extensive cycle programming, even complex processes can be simulated.

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DVD-2800 Features

• Temperature control and specimen temperature is determined optically. An exclusive full-range pyrometer covers the operating range seamlessly from ambient to 2800°C. Optionally, the standard graphite dilatometer tube is made to be interchangeable with alumina or silica tubes for special applications.
• The digital displacement transducer used in the system is an absolute device with no periodic calibration requirements. It is free of short term drift and long term changes, as its accuracy is based on a very stable internal glass grating whose movement is optically monitored.
• The dilatometer head slides up and down on guide rods to expose the specimen holder from the furnace cavity. For smooth operation, the head-lifting mechanism is counter-balanced with constant force springs. When inserted, sliding hermetic seals close the cavity to provide a protective environment for the specimen. Critical components, such as the seals, the base of the dilatometer head, the solid-state power controller, and the step-down power transformer are water cooled.

The vertical configuration of this device makes it especially suitable for testing ceramic or other powder pressed materials where shrinkage often accompanies heating. Pushrod tracking forces are governed by variable dead weight counterbalancing, and can be reduced to very low values. Optionally, loading can also be applied through additional weights.

Temperature Programming and Control

The DVD-2800 system offers a user programmable mix of ramps, dwells, soaks, and printing rates, delayed start, repeat-cycle capability with a program capacity of 16 thermal cycles (64 segments), and the ability to store and recall frequently used programs. The temperature program is fully displayed and is editable during a run. All vital test parameters are continuously displayed and updated. Digital temperature control with optimized adaptive routines is used to achieve accurate specimen, rather than furnace temperatures. Controlled heating rates up to 30°C/min and ballistic rates up to 100°C/min can be achieved.

The Discovery Dilatometer line features automated systems designed to measure the various thermophysical properties of solids. All instruments in this family use the Windows™ platform to interface to a personal computer, which can be provided as a turn-key system. An extensive tutorial is supplied with each instrument to allow self-teaching of the operation. On-line help screens are available in every phase of the program, greatly minimizing the need of referring back to the manual in case of questions while setting up or running a test.

Data Recording

Measured data is displayed in real time and is continuously stored for further analysis. All test and program parameters along with system correction and standards data are also stored in each test data set for easy comparison of tests at a later date.

System Correction and Calibration

Built-in system correction and calibration tables that can be verified or altered if desired are included. System correction can be altered, based on calibration runs with NIST standards or other references.

Data Reduction, Analysis, and Reporting

Stored data is automatically processed by statistical methods, for all points (such as with ramp heating, where applicable). The analysis includes polynomial curve fitting, and tabulation of results (such as percent expansion, average coefficient, and instantaneous coefficient, etc.) as a function of temperature. A variety of single or multiple curves for a group of tests can be generated, displayed, and hard copies printed. Optionally, data files may be transfered to other computers for remote processing.

Safety and Diagnostic Features

Built-in safety provisions guard against operational malfunctions and protect against failure of the system or destruction of the specimen. For example, loss of water flow, furnace and specimen over-temperature are among the functions that are continuously monitored. Some will automatically shut down the equipment while others alert the operator via audiovisual indicators. Diagnostic routines are available for system interrogation.