[time-nuts] New Timestamping / Time Interval Counter: the TICC

John Ackermann N8UR jra at febo.com
Sun Nov 27 09:43:40 EST 2016


Hi Luciano --

Glad to hear that!

The capability you asked for already exists (great minds think alike...)

In timestamp mode, the TICC will output the stamps for each channel 
independently, measured against the common 10 MHz reference.  So if both 
channels are active, you'll see a bunch of lines something like:

1.234567891234 chA
1.234567892345 chB
2.234567890434 chA
2.234567892789 chB

Recent beta versions of TimeLab can acquire multiple channels on a 
single serial port; there are a couple of magic setup commands in the 
"Acquire" dialog that will allow TimeLab to receive the above and 
display it as two separate traces.

There is also a three-cornered-hat capability, though it's a bit of a 
hack.  The TICC has a "TimeLab" mode which will output two timestamps as 
above, but in addition "chC" which is the time interval (B-A).

Since TimeLab requires all the input signals to be in the same format, 
the chC output is munged into a fake timestamp like this (adding the 
integer part of chB to the B-A difference):

1.234567891234 chA
1.234567892345 chB
1.000000001111 chC
2.234567890434 chA
2.234567892789 chB
2.000000002355 chC

With both TICC and TimeLab configured this way, you can do 
three-cornered-hat measurements in real time, which is pretty cool.

When I get a chance, I'll document the setup for this in the TICC 
operation manual.

John
----
On 11/27/2016 07:36 AM, timeok wrote:
>
>     Hi John,
> I have planned to buy two TICC.
> An interesting feature would be to be able to do two simultaneous acquisitions,
> and Timelab as real time display,using the two indipendent input channels and the 10Mhz clock as single reference.
> Luciano
> www.timeok.it
>
>
>     From "time-nuts" time-nuts-bounces at febo.com
>     To "Discussion of precise time and frequency measurement" time-nuts at febo.com
>     Cc
>     Date Wed, 23 Nov 2016 10:48:57 -0500
>     Subject [time-nuts] New Timestamping / Time Interval Counter: the TICC
>     Counters with resolution below 1 nanosecond are difficult. They require
>     either outrageous clock speeds, or interpolators that are typically a
>     bunch of analog components mixed with black magic and stirred by
>     frequent calibration. The very best single-shot resolution that's been
>     commercially available is 22 picoseconds in the HP 5370A/B, with jitter
>     somewhat more than that. My 5370B has an one-second noise ADEV of about
>     4x10e-11.
>
>     With the help of some very talented friends, I've been working on a new
>     counter called the "TICC" with <60ps resolution and similar jitter,
>     based the Texas Instruments TDC7200 time-to-data-converter chip. The
>     noise ADEV is about 7x10e-11, not much worse than the 5370,
>     but here's the trick: the TICC is an Arduino shield (mounting a Mega
>     2560 controller) that weighs a couple of ounces, requires *no*
>     calibration, and is powered from a USB cable!
>
>     The TICC is implemented as a two-channel timestamping counter. That
>     means it can measure or two low-frequency (e.g., pulse-per-second)
>     inputs against an external 10 MHz reference, or it can do a traditional
>     time interval measurement of input against the other. It can also
>     measure period, ratio, or any other function of two-channel timestamp
>     data. (And by the way -- multiple TICCs can be connected to yield 4, 6,
>     8, or more synchronized channels, though we haven't tested this
>     capability yet.)
>
>     I've attached a picture of the TICC prototype as well as an ADEV plot of
>     a 17+ day run of multiple measurements taken by two TICCs, and also
>     showing the TICC noise floor. The good news behind that plot is that
>     there are more than 6 million data points behind these results, and
>     there was not a single glitch or significant outlier among them.
>
>     There's more information available at http://febo.com/pages/TICC
>
>     The software is open source (BSD license) and is available at
>     https://github.com/TAPR/TICC -- the current version seems be reliable
>     but there are still features to add and a *lot* of cleanup to do; it's
>     currently ugly and very much a work in process.
>
>     As always, I'll be making the TICC available through TAPR. We're still
>     finalizing details, but we expect the price to be less than $200 for a
>     turn-key system: TICC mounted an Arduino with software loaded and
>     tested for basic functionality. We hope to ship the TICC by February.
>
>     I'll post a note in a week or two with final price and ordering
>     information. As a heads up, we will probably offer a small discount for
>     pre-orders. TAPR is a shoestring non-profit group and the up-front cost
>     to manufacture this unit will frankly be a challenge for us. Getting
>     pre-orders will help our cash flow significantly, so we ask you to keep
>     that in mind.
>
>     John
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