The "volume" you're looking at is almost certainly TICK volume. In which case it would equal the selected tick size of the chart. It's NOT exactly the same thing as a constant volume chart. Although through some trial and error you can come up with a tick setting that, averaged over time, would approximate a particular constant volume chart. For example say over a protracted period of time the average tick size of the underlying instrument you're charting is 10 contracts per tick. Generally speaking a 100 tick chart would roughly approximate a 1000 constant volume setting. Not perfectly but especially with larger settings in most cases you won't be able to tell much difference. Very small tick/volume settings on the other hand would tend to show bigger differences I should think.
Personally I use a 16807 CVB (Constant Volume Bar) ES Chart for intraday trading. It is a little slow but I like slow. Other prefer a 2401 CVB Chart. It gives you about 7 times the oscillations per day so more trading opportunities. It's a little fast for me but to each their own. All of my charts are increments of 7.
Tick = Transaction Trader ONE = trades 100 contracts per transaction Trader TWO = trades 1 contract per transaction Trader ONE and Trader TWO each place a trade. Both trades register as a single tick or transaction but Trader ONE's trade is 100 times more volume than Trader TWO. This is the variable aspect of Tick Charts that render them totally inconsistent. The picture you posted is "Ticks per bar" not Volume per bar. Tradestation doesn't offer Constant or capped Volume Bar Charts.
Tradestation isn't smart enough to cap the volume of their bar charts. They've been asked to do so more times than I have bones in my body but their response has always been, "It is too costly to program them correctly". The probelm is that it would take a qualified programmer about one day to fix them but Tradestation isn't interested in customer service. Example: You create a 500 share bar chart and the current bar contains 450 shares. The next tick comes in and it contains 150 shares. Tradestation is lazy and tacks on the entire 150 shares to the current bar making it a 600 share bar instead of doing it correctly and capping the current bar at 500 and taking the left over 100 shares to create the next bar. Doing a job correctly isn't Tradestation's "Job One".
I use MultiCharts. I developed CVB Bars first for Ensign but they are too much of an end user trading package. MultiCharts is more of a professional trader's tool. These are the only two software programs I personally know that create the CVB Charts correctly. Others have stated that Sierra Charts does but I have never been able to verify it.
Damn, I use TS for a datafeed so that means no constant volume bars. I'm not going to dump TS, so what do you recommend?
Consistency of scaling of the charts. It's a perfect transition from Scalping charts to Intraday charts to slow Intraday charts to Swing Charts to Long Term Charts to . . .etc.