Normally you should have an option to convert your TG signal into DTG if you use a commercial software. But if you don't have this option, you extract your TGA data as .txt or ;dat  and open it in excel. You can then, easly derive it as a function of time or temperature to obtain DTG curve.      

All actual TG softwares allow to do this, but if you have an old one, you may need to recover all the data and introduce them into another software. Just be careful that points are separated by the same "distance" (in terms of time or temperature, which should be proportional with each other), otherwise derivating may give strange results. If your data points are not equally separated, you should interpolate the missing points. Kaleidagraph software allows doing this. Then, the derivative will be very smooth and nice.

Alain

Thanks to  Mr.Atilla and Mr.Alain

Dear Karuppasamy

In fact you can derive the TGA curve in excel, nevertheless, I suggest you to take in to account that even if your points have equal spacing, you can obtain a DTG curve with a lot of "noise". if this occurs, the usage of a higher number of points in the calculations of the derivative curve, should be considered.

Regards

Nuno Vitorino

This answer follows from others. To calculate DTG independently of TGA instrument software, transfer data to a spreadsheet and calculate each pair of data, except the first value: m/t = {mi - m(i-1)}/{ti - t(i-1)} where m is the mass (either in mg or %) and t is the time (usually min is used), i is the datum under consideration (subscripts are not available here), m/t is the derivative (DTG) in mg/min or %/min. That is from each mass and time datum pair subtract the prior values and ratio them.

As stated in other replies, noise is increased in the DTG curve. The data can be smoothed or calculation of DTG can be based upon more than just pairs of values; taking 5 to 10 values for each calculation is the equivalent of a moving average.

Another useful way to compare TGA or DTG of mixtures is to calculate synthetic TGA or DTG curves by summing the curves of components in the ratio they are present in the mixture, then compare with the experimental curves of the mixture. Subtracting the synthetic curves from the experimental curves will reveal synergism (+ve differences) or antagonism (-ve differences), depending on which way the data is to be interpreted.

Plot the TGA graph in OriginPro software. Then go to the analysis tab. Differentiate it. You may get a noisey one. You will find the smoothing option the same analysis tab. Select the Adjacent-Averaging option. Adjust the point of window as per need. Set the boundary condition as extrapolate and recalculate option as auto. During the process enable the auto preview option to monitor the change.

I think it can help. Good luck.

Thank you very much

thank you so much, i got it too 

and how can I convert dTG unit from mg/min  to  %/C. Now I can not change it from the software, but I have the excel data.

Thank you all for comments! I got how to do it.

To remove noise from the DTG data you can use exponential smoothing in Excel. For this follow the way: DATA=>data analyses=>exponential smoothing.Typically damping factor is 0.9.

If there is no 'data analyses' button in your excel your need to add 'Analyses ToolPak' (File=>options=>adds-in=>analyses toolpak=> go).

The procedure was taken from here

http://www.excel-easy.com/examples/exponential-smoothing.html

Thank you so much Debabrata Das :)

Is there a way to do this using the Universal Analysis software?

You have to be able to numerically differentiate. There are many different difference schemes that can be used here. You can use a three-point scheme (eg approximation by a quadratic function), but due to the high variability of m = f (T) it is better to use a five-point or seven-point scheme. Data filtration procedure (noise) may also be needed. Regards,

Dear Karuppasamy R,

DTG plot is the derivative plot of TGA. The weight loss is differentiated with respect to time and then the as-obtained values are plotted against the temperature.

You can easily perform this by plotting the weight loss a y-axis and time in x-axis, followed by drawing the derivative plot. Extract the derivative data from window and plot those against temperature.

Thanking you very much.

Hi, I have a question, in the proposed equation m / t = {mi - m (i-1)} / {ti - t (i-1)}, what is the value of i? or where is it obtained? Is the initial mass? Thank you

Useful discussion.

m / t = {mi - m (i-1)} / {ti - t (i-1)} mi -initial weight of the sample

i -weight loss at particular temperature eg if ur noting for 30 C ,then note the wt loss for that temperatuure.

Thank you so much, I found your information very useful.

i compute that by the origin program

Prof suzy Ebrahim, please can you guide me on how you get your DTG from your TGA

Karuppasamy ... Modern instruments furnish the derivative thermogravimetry (DTG) simultaneously with the normal TG curve. If this possibility does not exist, with some older instruments you need to calculate DTG curve point by point. We divide the TG curve into segments where the x-axis is the time. We add the values of weight at the start of each TG step with the next value of the first segment and get the average by division by 2. The result is placed in a table against the average time. The second weight value will then be added to the third value and again the mean value is put in the table against the average temperature. ... and so no until the TG step is terminated. Now plot the results in the table. You will get a peak for each TG step.... Regards

Hello, here I would like to put a video about how to convert the data of TG to DT; if anyone needs to take a 1st derivative of the data, it is well explained.

https://www.youtube.com/watch?v=Dn0nYsRjgPI&ab_channel=JakeSeiler

I did the same...

This is great

Kindly follow this link to learn how to plot DTG curve from TGA curve

https://www.youtube.com/watch?v=inQWSnTOZ2M

I recommend Dr. Öykü Ataytür answer. Thanks

how to fix Duplicate x values will cause derivatives to be missing values.

Thanks

Thus, it can be said that the DTG curve can be drawn through the results of the TGA, either through the computer unit of the measuring instrument or by using a program such as excel.

Thanks for all the contributions. First, I watched the video shared by Öykü Ataytür, then I applied the formula shared by Robert A. Shanks and got the results.