For measurements that require sealing, the sample support tube has to have approximately the same diameter as the sample itself.

For other measurements, a ceramic support plate can be placed between the support tube and the sample. This allows the customer to measure also on smaller samples than the support tube itself.

HOWEVER: It is NOT practically possible to seal a disk onto such a support plate, since you then have to seal both the plate to the tube and the sample to the plate. Use of the plate is only suitable for measuring conductivity on samples smaller than the inner tube diameter of the support tube you have.

Standard support tube diameter is 20 mm. This tube diameter gives enough space for and easy mounting of gas tubes, electrode contacts and thermocouple(s) both on the inside and on the outside of the tube.

We do not normally recommend the 10 mm tube as the space on the inside of the tube is restricted and makes it a bit tricky to mount the inner gas tube and inner electrode contact. Also, as a consequence, the inner gas tube needs to be thinner than standard. Sealing such small samples can in addition be challenging.

If you choose 24 mm tube, the sample diameter can not be larger than that because of the restricted space between the sample/tube and the enclosing tube. The use of this tube will therefore require thinner outer gas tubes.