Do I set the delta T in AVA? Note: for an introduction to delta T, please see the separate FAQ entry ‘What is delta T?’. Under normal circumstances, you cannot set delta T in AVA – it is not applicable. If, as we recommend, you plug the Pt100 temperature probe directly into the circulator (e.g. Huber) and have it configured like this in AVA (in the circulator properties box, for ‘External temperature probe connected to circulator?’, ‘Yes’ is selected) then the circulator is responsible for the temperature control. If you implement a Tr (reaction temperature) setpoint/ramp, AVA will send Tr instructions to the circulator, and the circulator will calculate the required Tj (jacket temperature). In these circumstances, you should set the delta T limit in the circulator controller itself (not in AVA). The circulator is responsible for measuring and responding to the delta T. If the reactor Pt100 is separate from the circulator, you do set delta T in AVA. It is possible (e.g. if the circulator does not have a Pt100 socket) to plug the Pt100 for the reactor into the Data Hub instead and set up the Apparatus like this in AVA (in the circulator properties box, for ‘External temperature probe connected to circulator?’, select ‘No’, then click on the outline of a temperature probe in the reactor to add a Pt100 there) and then when you click on the circulator properties box, you will see that the field ‘Maximum temperature difference Tr – Tj’ has appeared. In this case, when you set Tr, AVA calculates the Tj and sends the Tj instructions to the circulator, considering the delta T limit set in AVA.