The IntelliChlor, measures salt when it initially starts up, and then every 12 hours after that.. There is no button to push to measure the salt level.
In my opinion, all Saltwater pool owners need to be able to test and determine what the "actual" salt level is in their pools, so that they can compare it with the "Reported" salt level that comes from the cell.. This is important as they can be very different..
From the cell's point of view, it is always right.. So, it is best to keep the cell happy.. so that it will generate chlorine. When the actual and reported salt levels get too far apart, it is usually time to replace the flow switch. There is a thermistor inside the flow switch that tends to go bad and can give you false high or low salt readings..
Edit... As long as the cell is happy, and the actual salt level in the pool does not bother you, then you don't need to worry about it.
Thanks,
Jim R.