Honeywell SMV800, User Manual

Page: 39 / 220

Revision 1.0 SMV800 Modbus User's Guide Page 27
ATTENTION:
•
The default engineering units for volumetric flow rate is cubic feets per
seconds and pound is the default engineering units for mass flow rate.
•
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 the LRV first.
Damping
Adjust the damping time constant for flow measurement to reduce the output noise. We suggest
that you set the damping to the smallest value that is reasonable for the process.
The damping values (in seconds) for flow are:
0.00
d
, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0,
10.0, 50.0 and100.0
Adjust the damping time to reduce the output noise. We recommend that you set the damping to
the largest value that the transmitter can accept.
Low Flow Cutoff
For calculated flow rate, set low and high cutoff limits between 0 and 30% of the upper range limit
(URL) for flow.
•
Low Flow Cutoff: Low (0.0 = default) High (0.0 = default)
Change the High value before editing Low value.
Background
You can set low and high flow cutoff limits for the transmitter output based on the calculated
variable Flow. The transmitter will clamp the flow output at zero flow when the flow rate reaches
the configured low limit and will keep the flow output at zero until the flow rate rises to the
configured high limit. This helps avoid errors caused by flow pulsations in range values close to
zero. Note that you configure limit values in selected engineering units between 0 to 30% of the
upper range limit for Flow. If either simulation of flow is enabled or reverse flow is enabled then
low and high cut off values have no effect on flow output.