It's capped at a maximum of 3-4 per second, but may be less than that depending on market activity. Agree about the volume based bars. In my experience volume from TWS is accurate.
Man, you'll have to stop using these cooking analogies He said that he doesn't know why, but the IB tick chart appears smoother to him. Simply put the IB version is a filtered version - actually it is a sampled version as dcraig correctly pointed out - and this will most likely (depending on how IB does it) have a low-pass filtering effect thus the perceived smoothness. Having said all that, the Bottom line is this. If the IB tick chart rocks his equity curve, then who cares! At the end isn't that all that matters? Just my 1/4 ...errr... 0.25c
It makes little difference if you aggregate things at a later stage (in your chart for example). Of course it depends on the difference in magnitude of the two samplings. Its more like baking a cake and adding each grain of flower individualy compared to adding it in cups (constant volume sampes) It seems to be widely rumored that some instruments on some exchanges (e.g. Globex & Eurex) under some circumstance (fast markets maybe?) are aggegated at source anyway. Cheers.
BF, That is no rumor. Globex destroyed the constant ticks by aggregating the transactions but that isn't the case with volume bars. they break the transactions down to their smallest increment (shares or contracts) before they build the bar. This is why capped volume bar charts ar far superior.