[time-nuts] New Timestamping / Time Interval Counter: the TICC
kb8tq at n1k.org
Wed Nov 23 13:10:42 EST 2016
> On Nov 23, 2016, at 10:48 AM, John Ackermann N8UR <jra at febo.com> wrote:
> 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 on the Texas Instruments TDC7200 time-to-data-converter chip. The one-second noise ADEV is about 7x10e-11, not much worse than the 5370, but here's the trick: the TICC is an Arduino shield (mounting on a Mega 2560 controller) that weighs only 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 one 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 one 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 on 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.
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