irig-b resolution

[podoro]

Hello,

I read that irig-b resolution is 10 ms but actual timecode generators usually have a resolution better than 1 µs.

I'm looking for some elaboration on this since I do not understand. Does the 10 ms resolution mean that the actual time provided by irig-b error could be up to 10 ms off from actual time? If so, would the 1 µs resolution apply in addition the to existing error?

Also, I'm not sure if this is the best place to ask but I thought I would throw it in since there is not a lot of information on the web on irig-b. If anyone has a recommendation for a low-cost irig-b signal generator, please let me know. I am not concerned with the actual time value being correct but I would like to have an irig-b signal on a coax line to work with. I've been watching generators on ebay but am hoping to find something in the sub-$100 price range.

Thanks.

 

[IRstuff]

?? The very first hit in Google is the specification for IRIG STANDARD 200-98

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[podoro]

Yeah, saw that spec, if it answers my question I didn't catch it.

I didn't actually have the question until I was a bit further down the list. Hit #36 for "irig-b resolution" Google search was one of your posts here from 2002, IRstuff. I'm hoping you can help me with my confusion...

If IRIG-B resolution is 10 ms, and a timecode generator resolution is 1 ns, does that mean that each pulse will be +/- 1 ns after the previous pulse but the timecode data on each individual pulse may be +/- 10 ms due to the IRIG-B resolution itself?

 

[VEBill]

"Does the 10 ms resolution mean... ...up to 10 ms off from actual time?"

First thing is to distinguish between resolution and accuracy. A time signal can be low resolution yet extremely accurate. For example a simple 1 pps pulse train only identifies time to the nearest second resolution (referencing absolute time using other more informative references), but often does so to extremely high accuracy (perhaps within a us).

For the code resolution, start with Wiki (but check it against better references). It states "...Typical commercial devices will synchronize to within 1 microsecond using IRIG B timecodes."

Once the client (slave) device has synchronized, it can itself break up absolute time into finer units. Just like setting your watch to the dropping ball in Greenwich.

 

[podoro]

Thanks for pointing out my misunderstanding VE1BLL.