Hi all,
you can try Caddock resistor networks (Caddock electronics)
They have precision networks, i don't know if they have R-2R anyway.
Alain
F4GBC
----- Original Message -----
From: "Bruce Griffiths" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Wednesday, October 07, 2009 1:43 AM
Subject: Re: [time-nuts] DAC resistors
Neville Michie wrote:
Hi,
I am constructing a phase meter to monitor the phase creep of clocks.
It consists of a BCD counter counting say microseconds that has its
count strobed into a latch by a pulse from the clock.
The Latch drives a DAC which drives a pen recorder and an analogue
data logger.
Now I am familiar with R - 2R networks, and that method is used on
each decade
but the resistors that combine the decades in a 10:1 ratio are the
problem.
I have an approximate value, and I will probably have to trim them to
eliminate
digital errors later.
But I can not find a reference anywhere to how to calculate the correct
resistors or even a working example except for an old Analog Devices
data sheet which seems to use a different structure, by reducing the
supply voltage of each decade.
Can anyone Help?
Cheers, Neville Michie
Neville
If there was an easier method it would probably have been used.
It is probably simpler to use a different structure than the R-2R ladder.
For example the R, 2R, 4R, 8R connected to a summing bus followed by a
4.8R interstage resistor connecting to the summing bus of the next
decade etc works well.
See attached partial circuit for details.
Bruce
--------------------------------------------------------------------------------
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
