Honeywell SMV800, User Manual

Page: 34 / 220

Page 22 SMV800 Modbus User's Guide Revision 1.0
Background
Internally, the SMV transmitter uses absolute pressure values for all flow calculations. The value
entered in the Atmospheric Offset field is added to the gauge pressure input value to approximate the
absolute pressure.
An inaccurate atmospheric pressure offset value will result in a small error of the flow calculation.
Use an absolute pressure gauge to measure the correct atmospheric pressure. A standard barometer may
not give an accurate absolute pressure reading.
SP (AP/GP or SP) Range Values (LRV and URV)
The Lower Range Value and the Upper Range Value fields for SP are found on the
Static Pressure
Config tab.
Set the LRV (which is the process input for 0% output) and URV (which is the process input for
100% output) for the static pressure input.

LRV, Enter the lower range value (default value is 0.0)

URV, Enter the upper range value
default values for URV based on model are:
50 psia for model SMA810750 psia for model SMA845,
3000 psig for model SMG870
NOTE: Static pressure may be absolute or gauge pressure, depending on the model SMV800 you
have selected.
ATTENTION: The range for static pressure is (as
measured at the high-pressure port of the meter body).
The range for static pressure is (as measured at the high-pressure port of the meter body).
•
The URV changes automatically to compensate for any changes in the LRV and maintain
the present span (URV – LRV).
•
If you must change both the LRV and URV, always change LRV first.
Damping
Adjust the damping time constant for Static Pressure to reduce the output noise. Default value of
damping is 0.5 seconds.