The
MPS Flow Sensor product page states the following:
Installation note:
For an accurate measurement we recommend to use a straight piece of tubing with a min. length of 5 cm before and after the sensor. The sensor itself should not be equipped with angled fittings.
As to the DP Ultra foaming, I am not sure. I also used the DP Ultra and have no foaming issues.
Did you add any additives, and/or Is all the air removed from your loop?