OK, Follows (in several editions!) the theory of and how to operate a DMTD system to get the best results out of it.
Once hooked up as shown and you have the PC showing the counts we can start to take data.
In the following example the RF inputs are 5MHz, the offset is 1Hz, and the counter is an 8 digit counter with a 10ns resolution. Also I am taking data with HyperTerminal and using Ulrich Bangert's PLOTTER program.
On the PC screen you should see the counts occurring once per second and the value will be either incrementing or decrementing.
0.xxxxxxxx
Adjust the fine frequency of the DUT or the REF to slow the rate of change and get into the low to midrange of the scale.
Now capture the data to a file for lets say 15 Minutes.
Then open plotter and make sure you input 1.00 into the Tau-0/s box
Select file and open and select the file you just saved via HyperTerminal.
Here is an example:
This is a 4K+ Second file of a HP5065A Rubidium versus an FTS 1200 Quartz.
This shows how the phase changed over time.
Full scale is 200nS and the LSB value is 2X10-15th.
Now if you want to plot the Allan Deviation you will need to remove the 2 wraps shown.
To do this click on "all steps"
Then select "I have no idea" and OK.
You should now see the full 4K+ plot without wraps.
One more step before you can compute the AD.
Click on Series on the top tool bar and then enter a name (I just enter a single letter lets say C), and the formula.
For this example the formula is 2.0e-15*x1 .
the 2.0e-15 represents the LSB value for the particular counter used.
You should now see a black line added to the plot and the box to the right now shows an added plot called C.
Deselect the Column 1 red plot and the black plot should expand to fit the screen.
Now click on Time Stability Statistics in the toolbar, select data is phase, use powers of 2, and normal Allan deviation reselecting Time Stability Statistics each time.
Finally select Time Stability Statistics one more time and select process.
You should now have the Allan Deviation plot! Shown is the plot for the examples data.
*******************************************************************************
One thing about the all steps, it does not do the best job!
I forgot this as I always manually remove them!
Instead of clicking on all steps do this.
Click on show single marker, then using the cursor position the marker so that it covers the left step.
Now click single step. You should see most of the step gone. Now using the cursor click on and out outline the remaining portion of the step. This zooms in. Position the single marker between the two vertical traces or on the single trace. If between two click +- 1 points until you are back to 1 line. Once there click single step again. Keep repeating until nothing happens when you click single step. Then click once on the +- 1 point button. Now click un-zoom on the tool bar. The right step will still be there. repeat the procedure to eliminate that step and un-zoom.
Now finally you can click on series and compute it.
Attached is a plot of the manually step removed Allan deviation so you can see the difference!
Blue is remove all (auto), and red is single step Manual)
Whew.
********************************************************************************
More follows over a couple days!