Thermophysical Properties Research Laboratory, Inc.
Phone : 765-463-1581
Dilatometer (ASTM E 228-06, ASTM C 372-94, ASTM D 696-08)
The push-rod dilatometer is used to measure the thermal expansion of a sample as
compared to a known expansion. Normal operation of the experiment would be to select a temperature range for the
sample to be tested under. This could include heating the sample to a specified temperature, then
holding that temperature for a given length of time, and the cooling the sample back down close to
room temperature. These options can be specified for the sample to tested.
The temperature range of the push-rod dilatometer is designed to heat a sample from room
temperature to 1500 degrees Celsius. This is done through the use of an electrical furnace
surrounding the sample and NIST standard. One of the modifications made to the dilatometer by
TPRL was to include routines for cryogenic studies. With this modifications a lower temperature of
-190 degrees Celsius can be obtained. This is done through the use of liquid nitrogen pumped into the
The environment of the push-rod dilatometer can be from a total vacuum to a mixture of different
gasses depending on the customer's requirements.
The procedure to testing the sample consists of selecting an appropriate standard to measure
against. The sample is measured to find its length. This is preferred to be 2.00 inches long. Please
note that the precision length of the sample must be known to properly calculate the expansion.
After the sample and standard are set in place, and the enclosing tube is placed over the experiment, a
vacuum pump is turned on. After the pressure inside the tube is below 1 torr, the pump may be
turned off and a inert gas of helium is feed in. The gas is to help prevent any possible reactions with
the sample at the higher temperatures.
After the samples are set in the dilatometer, the computer is programmed to run the experiment.
The computer controls the major functions of the experiment and records the temperature and the
difference between the standards expansion and the sample. From this data the computer can
calculate the actual expansion of the sample. The measurements are taken through the use of an HP
voltmeter. This information is then translated into the temperature and expansion difference.