The directly measured signal of DTA is the electrical voltage between sample crucible and reference crucible, typically expressed in µV (or in µV/mg, if the sample mass is taken into account). Because the voltage-temperature characteristic of the thermocouples of your DTA equipment is usually known by the computer that controls the measurement, these microvolts can easily be converted to a temperature difference. For modern DTA's, this are typically a very few degrees, or even less than a degree.

It is possible (and often recommended), however, to perform prior to the sample measurements calibration measurements with suitable substances. This could e.g. be melting of indium, of zinc, of gold, and some others. This way you have 1st a comparison of your measured melting points of the calibration substance with the expected values. E.g., zinc should melt at 419.6°C. Many DTA suppliers have the option to write the measured values and the expected into a table and to produce from this a "calibration file #1", that corrects the measured temperatures then to more accurate data. Besides, another "calibration file #2" can be created, where the measured melting peak areas of the calibration substances (given in µV*s/mg) are compared to the known heats of fusion of the calibration substances. From this, the dependence "sensitivity vs. temperature" of the measurement setup (furnace, sample holder, crucible type, gas, heating rate) is calculated. And this "calibration file #1" (or "sensitivity file") can be used to change DTA scaling from µV (or Kelvin) to mW. Usually the sensitivity becomes lower for higher temperatures. I am adding here a sensitivity calibration curve that I did measure for a NETZSCH STA 449 some years ago.

The directly measured signal of DTA is the electrical voltage between sample crucible and reference crucible, typically expressed in µV (or in µV/mg, if the sample mass is taken into account). Because the voltage-temperature characteristic of the thermocouples of your DTA equipment is usually known by the computer that controls the measurement, these microvolts can easily be converted to a temperature difference. For modern DTA's, this are typically a very few degrees, or even less than a degree.

It is possible (and often recommended), however, to perform prior to the sample measurements calibration measurements with suitable substances. This could e.g. be melting of indium, of zinc, of gold, and some others. This way you have 1st a comparison of your measured melting points of the calibration substance with the expected values. E.g., zinc should melt at 419.6°C. Many DTA suppliers have the option to write the measured values and the expected into a table and to produce from this a "calibration file #1", that corrects the measured temperatures then to more accurate data. Besides, another "calibration file #2" can be created, where the measured melting peak areas of the calibration substances (given in µV*s/mg) are compared to the known heats of fusion of the calibration substances. From this, the dependence "sensitivity vs. temperature" of the measurement setup (furnace, sample holder, crucible type, gas, heating rate) is calculated. And this "calibration file #1" (or "sensitivity file") can be used to change DTA scaling from µV (or Kelvin) to mW. Usually the sensitivity becomes lower for higher temperatures. I am adding here a sensitivity calibration curve that I did measure for a NETZSCH STA 449 some years ago.

The explanations given by Detlef Klimm are very accurate and I fully agree with him. Just one comment to the issue of calibration: the values of errors in T and sensivity should be corrected not only in relation to temperature, but also to heating rate. In my lab there is a Setaram's Labsys, which has software that calculates the calibration curves as the function of temperature and heating rate. After calibration, the raw signal in µV is converted to °C or K at T axis, mW at heat flow axis and from µV*s to mJ when calculating the transformation heat (after integration of the signal).

Coming back to your original question, the power-compensated DSC's raw signal is in mW, and the DTA's raw signal is in µV which directly come from the thermocouples' characteristics. Then, software is used to make the results looking similar.

Thank you both very much Detlef Klimm and Jarosław Ferenc for the informative answer.

Actually the results i have are from Setaram LABSYS evo TG/DSC/DTA analyzer, which according to your answer, explains why i received the results in mW directly for DTA. The lab engineer told me that he already made the calibrations required from the software and produced the results in mW.

Thank you very much for confirming this.