What is the difference between the nozzle of a bimetallic thermometer and a thermocouple

As a commonly used temperature instrument like bimetallic thermometers, thermocouples are commonly used temperature measuring components that directly measure temperature and convert temperature signals into thermoelectric potential signals, which are then converted into the temperature of the measured medium through process electrical instruments (secondary instruments). There is a significant difference in the nozzle between a bimetallic thermometer and a thermocouple (or thermistor).

Although the nozzle of a bimetallic thermometer and a thermocouple are both M27 * 2, the length of the threaded seal varies. If a bimetallic thermometer comes with a sleeve, its nozzle should be compatible with the thermocouple nozzle (if the thread specifications are the same). For a bimetallic thermometer without a sleeve, the connecting thread may not be M27x2 or 3/4NPT.

The connecting thread of the sleeve for thermocouples or thermal resistors is mostly M27x2 or 3/4NPT. If a bimetallic thermometer is equipped with a sleeve, its nozzle should be compatible with the thermocouple nozzle (if the thread specifications are the same). For bimetallic thermometers without sleeves, the connecting thread may not be M27x2 or 3/4NPT, and the internal thread processing drawings of the thermometer sleeve are different. These are standard parts. If it is non-standard, it can be the same according to the company's requirements.

Thermistors and thermocouples can have different connections, which are related to process prerequisites, pressure grade, pipeline size, etc. They do not need to be limited to threaded connections, but can also be flange connections, and M20 * 1.5 ect. There are indeed M27 * 2 thermal resistance tube sockets, but there is another specification that is in the imperial system, probably 3/4 ". This specification may seem similar to M27, but its pitch is different, so it must be careful in practical installation and replacement.