Thermocouple for Use in Annubar with Temperature Measurement

Presumably the temperature sensor is being used for mass flow calculations, perhaps along with absolute pressure in addition to the differential pressure produced by the Annubar. As RTD sensors tend to be more linear and more accurate than thermocouples, the main concern here is going to be the impact of the temperature sensor's inaccuracy on the calculated mass flow rate (assuming the temperature isn't so high that an RTD could not be used at all, which would be a very hot application!).

Check the manufacturer's specs on RTD versus thermocouple sensor accuracy, then calculate how much this temperature inaccuracy will affect the accuracy of the mass flow calculation based on the temperature-compensated mass flow equation this flowmeter uses. If it's all within your required spec for flow accuracy, you can use a thermocouple.