Honeywell HC900 - Table 94 Metric Units; Figure 85 RH Function Block Example

Function Blocks
RH Relative Humidity Function Block
Revision 11 HC900 Hybrid Control Designer Function Block Reference Guide 321
2/07
Metric system
Table 94 Metric units
Metric ON OFF
DRY °C °F
WET °C °F
PRES Pa PSI
TIP
It is physically impossible for the wet bulb to be warmer than the dry bulb. If this appears to be
the case, it implies a problem with the sensors, and will result in a RH greater than 100 %.
Downstream blocks should detect that situation and react promptly.
Example
HFigure 85 shows an RH function block example.
A setup parameter allows inputs to be in Degrees F or Degrees C. When Degrees F is selected, pressure is
assumed to be in PSIA. When Degrees C is selected, pressure is assumed to be in Pa. (101325 Pa = 1 std.
Atmosphere.
Figure 85 RH function block example