Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA) are both types of thermal analysis that compare heat information between a sample and a reference material. However, the similarities don’t stop there — both tests can provide information about glass transitions, melting points, sample purity, and crystallization.
So what’s the difference, and when might you choose one over the other? Here are the key differences across testing methods, instruments, and measurements.
The Difference Between DSC and DTA Methods
Characteristics of the DSC Method
DSC is a qualitative method that measures the changes in heat flow as a sample transforms from one state to another. In this testing method, the temperatures of both the sample and reference material are increased linearly over time.
Characteristics of the DTA Method
DTA is a semi-quantitative method used to observe the temperature differences between the sample and reference when the heat flow is constant. Identical heat flow is applied to the sample and reference when using this method.
The Bottom Line
Both methods compare the thermal properties of a sample and a reference material. DSC compares heat flow, whereas DTA evaluates how applied temperature affects a material’s temperature.
The Difference Between DSC and DTA Instruments
Features of DSC Instruments
There are two main types of DSC, and the main difference between the two is how the instruments used to conduct them are designed:
Heat Flux DSC Features
In Heat flux DSC, the sample and reference material are both placed on a single sample holder that has temperature sensors integrated into it for measurement. These samples are both heated at the same time by a single oven.
As the sample undergoes phase transition, there will be a significant temperature difference between it and the reference material also being heated. By measuring and calculating this difference, heat flux DSC determines heat flow data and can quantitatively measure physical quantities related to the phase change that occurred in the sample.
Heat flux DSC minimizes risk of the sample and reference material being exposed to different conditions at any point in the test cycle and maximizes the accuracy of measurements, provided the post-test calculations are completed correctly.
Power-compensated DSC uses two separate thermally-insulated furnaces to sample and reference material to be heated separately.
Power-compensated DSC systems use a very sensitive device called a Platinum Resistance Thermometer to detect the thermal event prompting phase change in the sample material. Both materials are heated at a constant rate until the thermal event occurs in the sample. At this point, the two furnaces compensate for power distribution (either adding more power to heat up the sample furnace or adding power to the other furnace to increase its temperature to match the sample’s) in order to maintain temperature equilibrium in both furnaces.
The amount of power required to maintain temperature equilibrium is measured as a direct proportion of the energy changes occurring in the sample undergoing phase change. Therefore, power-compensated DSC can provide more immediate testing results, as testers do not have to complete the equations of Heat Flux DSC, but the results may not be as highly accurate.
Features of DTA instruments
The defining characteristic of a DTA instrument is that it has two thermocouples connected to a voltmeter. DTA instruments also have a single furnace, a sample holder, sample containers, a ceramic or metallic block, a temperature programmer, and a recording system.
The Bottom Line
A DTA instrument has a single heater that works at higher temperatures, allowing you to simultaneously test a sample and a reference material in an aggressive environment. This can be helpful when testing minerals or other inorganic materials with a high melting point.
A DSC instrument enables users to subject the two materials to different amounts of heat, in order to measure the difference in heat flow required to keep the materials at the same temperature.
The Difference Between DSC and DTA Measurements
What DSC Measures
DSC measures the difference in heat flow required to keep a sample and reference material at the same temperature as it’s heated and cooled. DSC measures heat absorption and release when a material is exposed to thermal energy, which provides users with an understanding of the material’s endothermic and exothermic phase transitions. Key DSC measurements include Melting Temperature (Tm), Glass Transition (Tg), Specific Heat Capacity(Cp) , Heat of Enthalpy (∆H), oxidation induction time (OIT), Oxidative Onset Time (OOT) and isotherm performance.
What DTA Measures
DTA measures the difference in temperature between the sample and the reference when the applied heat is the same. Materials respond to temperatures in different ways, resulting in differential temperatures. Because of this, DTA can measure material conductivity and phase changes unrelated to enthalpy.
The Bottom Line
DSC measurements provide a more comprehensive range of information and detail. However, DTA measurements may be useful if you’re specifically interested in thermal properties and phase transitions unrelated to enthalpy.
When The Choice of Test Makes a Difference
A semi-quantitative method like DTA may be enough for a quick quality control check if you don’t need precise data. But when you need qualitative results about a material’s composition and performance, DSC is the superior choice.
There are a wide range of DSC analysis applications, including quality control, polymer testing and crystallinity testing. Contact us if you think that DSC may be the optimal analysis method for your project.
Innovatech Labs is a premier testing facility with over 30 years of history in providing accurate and timely results.