[time-nuts] Controlling FEI 5680A
EWKehren at aol.com
EWKehren at aol.com
Sat Jan 14 07:32:15 EST 2012
I have no expertise when it comes to filter design or programming PIC's or
other micro controllers. But I know what works for me. For 11 years I have
been using Shera controllers with very good results. (I still have some new
assembled extra A&A boards, if any one is interested, please contact me
off list) Over the years I have made hardware work around's and made my own
boards ending up with 120 and 240 samples and 100 MHz clock in stead of 24
MHz. Over time chips are harder to get. The solution is an Altera MAX 3000
gate array and that input circuit can be implemented on a $ 2 100 MHz
version or $ 5 200 MHz version using either a 100 MHz or 200 MHz clock. That
circuit works with the present Shera PIC but that is a 28 pin $ 4 device.
Since in this application the controller does not have to be all things
for all devices it would make sense to use a PIC16F688 or any other 14 pin
device. Brooks, if so inclined could do it or some one else if he would
allow it. For my personal use I can live with the present PIC and the work
around's that I have incorporated. The result is a $ 35 solution using an
I have laid out a board that once I know the pin assignments I will
gladly have made and furnish with G/A to the individual that will do the design.
An analog portion with opto couplers is also included.
The Gate Array solution is thanks to Juerg Koegel, a list member that has
worked with me on the Dual Mixer. The analog portion has been fully
functioning for two years but I had not found some one to test the counter part
with Ulrich's or Stable 32 plotter. Thanks to Juerg that is now done. Found
out that I had made a mistake in my thought process but we now have a fully
functioning counter with nice plotting results. Again thanks to Juerg a G/A
have replaced logic chips that soon may be hard to get. The first boards
are in and test results will be available soon. This is a 2 channel counter
in the ping pong mode that can be switched from period to phase allowing
set up with out the use of any other counter. 1 E-15 and 5 E-16 will be
Juerg is also helping me with the what I call the Austron circuit allowing
1E-12 resolution in one second. The first unit was a direct copy of the
Austron 2110 circuit using a dual stage Xtal filter the next one will use a
DDS for the offset. This will happen after the 5 channel counter test which
will allow cross correlation and 3 corner hat testing. Board is laid and
G/A's designed but we are waiting till the 2 channel is fully tested.
Juerg is also working on an interface board that will have a LCD display
and USB memory stick interface. That allows the D/M be operated independent
of a PC with plotting done by the PC after the test run, transferring the
data with the USB stick. RS232 or blue tooth is also an option. Richard
McCorkle was key in the design of the counters, thanks to his PIC expertise.
With out him the low cost solution would not have been possible.
This work will be followed by the Austron circuit and hopefully by a low
cost control loop.
Questions have been asked as to what I use for frequency testing. Because
of my work on signal generators I rely heavily on a HP 5345A counter that
gives me 40 GHz measurement capability. It with its internal 500MHz
reciprocal counting capability injecting noise into the 500 MHz it allows me 1 E
-12 over 1000 seconds. Combined with the Tracor 527E I can get 1 E-16 with the
last two digits of not much use. I like the 1000 sec gate time since it in
effect does some averaging. My testing of the 56680A is done with the 5345
with out the Tracor.
I also use the Austron 2110 for longer time testing. In the past it was
tied to Loran C now to Tbolt.
As frequency sources I use a HP 5061 B, HP 5062 C a FRK-H using a Shera
controller and Tbolt. The FRK is presently out on loan. In the past I used a
GPS receiver, now I use the Tbolt. The plan is to have it tested against a
I hope this answers a lot of questions. What is needed is that some one
steps up to the plate and does the controller. To me the appeal is the $15
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