Reading Temp of Liquid in a High pressure pipe

Hi, Im looking for ideas and options of any possible sensors of probes to read the temp of flowing liquid in a metal pipe, the liquid is under hi pressure the temp ranges from 0DegC to about 300DegC.

I will be able to weld in any bungs needs to tap into the metal pipe but needs some sensor options, anyone ever do this before and have some options ?

Thanks in advance.

Thermowells are the standard industrial way of installing thermocouple sensors into pipes and vessels.


It will be pretty close if you put a high temperature thermistor in contact with the outside surface of the pipe and put a little lagging around the pipe at that point to isolate it from the surrounding air. Saves a lot of work and worries about what the liquid and preesure will do to the sensor. You can improve its sensitivity with some heatsink compound between the thermistor and the pipe.

You'll be above the normal range of thermistors at 300C Suggest you use a type K thermocouple. However the output is onlyabout 12.2 millivolts at 300C and you will (may) need cold junction compensation to allow for variable ambient temperature. Both these problems are resolved by using a thermocouple amplifier module which wil boost the reading to something more sensible for the arduino input and also provide compensation for the ambient temperature.

As to inserting it into the fluid stream, unless your pipework is of large diameter (say > 3") and the fluid flow is truly laminar (very unlikely) I'd avoid the use of any form of insertion device. As Pluggy says, simply strapping it tightly to the outside of the line and providing line insulation for several inches both upstream and downstream of the measured point will give you the fluid temperature. There will be a slight time lag since any temperature change in the fluid will take time to pass to the outside wall, but the use of an insertion measurement device (such as a thermowell) would also experience this time delay.