The ProboStat can be used to measure Seebeck coefficient in many ways. The standard method is to suspend a bar sample between two thermocouple tips and measure temperatures at both ends and then the sample voltage between the + or - leads of the thermocouples, or use separate electrodes for sample voltage measurement as in the picture.
Temperature gradient over the sample is either naturally occurring furnace gradient or one induced by small internal heater placed above the spring load top plate. This method can also be used in combination with 4-point conductivity measurement.
This method can be be done from ambient temperature up to 1600ºC, from vacuum to high pressure (high pressure option), with any type of gas atmosphere.
Best results are achieved with bar sample of 3-4 cm length. Sample may be of arbitary shape but it is easier to mount if the sample is bar shaped with longer length than cross section.Disc and thin film samples are not mounted as easily as bars and the electrode contacts may have to be glued (with Pt ink) to the side (since the film only covers the side and not the ends of the sample).
There is no clear limit how small samples can be measured, but as the sizes go smaller the mounting gets harder and more importantly the ratio between signal and error gets less favourable.
This method involves reading two thermocouple voltages and the sample voltage, converting the thermocouple voltages to temperatures, calculating the temperature difference and plotting the sample voltage against the temperature difference. This can be performaed by the user or automatically with the Omega software. NorECs can provide with full system (including ProboStat sample holder, furnace, Omega software, multimeter and power supply for the internal heater) that can automatically perform all the tasks needed for determining Seebeck coefficient at various temperatures.
ProboStat and Omega offer well proven and repeatable way of measuring Seebeck coefficients but also allows user great freedom to alter the setup to match for the specific qualities and challenges each individual sample has. This freedom and control over every aspect is the key to reach accurate result164 and is missing in 'turn-key' systems.
It is possible to combine this method with four point resistance measurement by adding two additional electrodes on the sample, see combined Seebeck coefficient and conductivity measurement
Seebsys - Combined Seebeck coefficient and resistance measurement system