Sierra INNOVA 215 - Manual (Page 9)

IM-215 Rev-A.1 Series Innova-Switch™ Page 9 of 42
FIGURE 2A: RELATIVE CHANGE IN RESPONSE OF A HEATED RTD IMMERSED
IN VARIOUS MEDIA
2.2
Flow Switching
Most mass flow monitoring techniques calculate mass indirectly by measuring
volumetric flow such as gallons per minute or cubic cm per second, then either measure
density separately or calculate it from temperature measurements of the fluid and,
finally, combine density and volumetric flow to obtain mass flow. The SIERRA
INSTRUMENTS thermal-differential technique is one of two methods that directly
measure the mass flow. For ease of comparison most flow applications are presented
in terms of velocity which is independent of the flow cross sectional area (i.e. feet per
second (FPS)). The true mass flow equivalent would be FPS multiplied by density but
for simplicity FPS is used and density effects are ignored. This is normally not critical for
flow switching applications.