ZMF-II clock accuracy

I read in another topic (http://www.chess.com/forum/view/chess-equipment/zmf-ii-led-chess-clocks?page=3) that bananaboatcaptain had found the ZMF-II to be inaccurate in count-up mode, but someone else responded that it was fine in countdown mode.

I purchased the clock on Amazon and did my own test in countdown mode by comparing the clock to Time.gov (USNO). I found that over the course of an hour, the ZMF-II was 25 seconds too fast. I performed the same test on my trusty DGT960 (the folding one with the orange buttons), and found no detectable inaccuracy at all. I contacted Zmart and left my honest feedback on Amazon.

What are we to make of this? The ZMF-II is gaining popularity. In fact, I love the LED display, and my only other complaint is that the increment is added before your turn rather than after. (And the LED indicators can be too bright from certain angles.) But isn't 25 seconds/hour too inaccurate?

And are there other chess clocks that we've unknowingly been using that are inaccurate? (Besides the analogs, of course.) 

If it works perfectly fine in countdown mode, then shouldn't it be okay for chess? The only game that I know of that uses countup mode is Scrabble.

As I said, it does NOT work perfectly fine in countdown mode. My test was in countdown mode.

Oh, I thought you were talking about the countup mode.

I have a ZMF II that I bought two weeks ago, I never thought about testing it.  Thanks for the heads up, I am starting the test now. 

I've also got the Seiko Mephisto that belongs to a friend sitting here, I'm going to run them side by side against the Naval Observatory time site for an hour.

Hi, you should tested in the chess mode. Don't use the count up or count down mode. Mine is accurate.

MikeH76, what do you mean? I tested it by setting the clock to G60, just as one might in a chess tournament [albeit with no delay], and then letting one player's clock run down. 

I tested mine in tournament mode and it was fine.

I didn't test mine and it was fine too.

-Izmet

I tested mine again and the result is the same: 24 or 25 seconds too fast in the course of an hour. The manufacturer has just informed me that a bug in the software has been corrected for subsequent production runs (although he told me he only knew of the clock being off 3 seconds/hour). 

Neither the Seiko nor the ZMF deviated by as much as a second at 45 min, 30 min, 15 min or zero.  They are at least accurate as the on-line official time standard site as far as can be determined watching the read-out.  Seem as good as my $100 digital watch too.

Maybe after some time, in a month or two, I'll try it again to see if the battery age makes any difference.  But an "electronics" guy here says that should not make any difference until it goes dead, with the battery it's accurate or doesn't work, no inbetween.  Something about their being plenty of juice to power the timer chip long after the juice is too low to power the read-out or such like.

Yeah, it may just be that I got a defective clock. Zmart says the firmware was corrected, so I probably just got a clock from some old production run. Hopefully there aren't a significant number of defective clocks out there.

I would recommend that if you have a ZMF-II, that you test it against time.gov to make sure your firmware is not the old buggy version.

Dude, don't use the Internet to test a clock. Use your watch clock.

I'm testing my Excalibur GameTime, just curious, I haven't heard anything bad about it but I just wanted to try it out.

I used the U.S. Naval Observatory time site and my watch.  Absolutely no discrepancies at all are far as I can see by watching the read-outs.  None.

But to the OP, did ZMF offer any recompense for having sold you a unit which they acknowledge had problems? 

As long as it isn't off my some huge amount and both players get the same amount of time, it should be fine, correct? I'm not saying that it is good for the clock to be inaccurate.

Yes, they're replacing it for free. I actually bought it from Wholesalechess.com, not directly from Zmartfun.

I've only had mine for a few weeks, and really like it.  Hearing you say that makes me feel even better about my choice.   Sounds like ZMF really stepped up.  Kudos.

Indeed, they were very gracious. I hope my comments here did not deter anyone from buying the clock. If anything, buy it directly from Zmart so you're sure to get the most recent run. I must say I found the clock otherwise to be a delight. I'll post an update when I get and test the replacement.

I am 48 minutes through my GameTime test and it looks close enough to perfect (less than 1/2 second). I'll test my DGT North American when I get it in the mail on Monday.