The Robic SC-505W stopwatch is advertised as being 1/1000th second precision to 24 hours. I purchased two of these units as timers for a test pinewood derby track, which requires high accuracy over about a 2 second range. I carefully opened the units up and connected an external electronic trigger circuit to their start/stop and reset buttons. To test the two units, I used the electronic trigger circuit to trigger their start/stop buttons at the exact same time. I also connected a digital oscilloscope to the trigger circuits and start/stop buttons to confirm the integrity of the test. What I found was that there was up to a +-40/1000 of a second difference between the two test units over a 2 second period of time! The test was repeated 20 times; in 6 cases the times were identical, in 5 cases sample A had a greater time, and in 9 cases sample B had a greater time. In otherwords, the error was not repeatable, therefore, I could not simply offset the error and still use the SC-505W units as timers.

I later called the distributor for Robic and explained what I had found. The representative stated that the units were accurate to something like 2 seconds over a 1 year period of time. I explained that I was not looking for accuracy over 1 year, rather accuracy over a time period less than 10 seconds. His final statement was “what do you expect from a stopwatch”.

In fairness to Robic, I tested another inexpensive timer and found similiar results, but that timer at least only advertised 1/100th second precision. I should also point out that the internal and external construction of the SC-505W was very rugged. But, it is simply not accurate, even at 1/100th second precision, never mind 1/1000th precision.

I expected a stopwatch time that would do SPLITS and then…give me the FINAL TIME of the race, which this doesn’t. This NOT what a coach would want and wish I could upgrade. 🙁

I’ve had many Robic timers in various colors. Great consistent product.