Rosemount 3491, Reference Manual, Page: 102 / 152

Reference Manual
00809-0100-4841, Rev. AA
May 2007
Rosemount 3490 Series
4-70
Example 2
Consider a flow measurement application where the PV value is a flow rate in
units of cubic metres per hour (m3/hour).
As the totalisers are set-up to operate with an input of flow in units of
flow/second, the input of m
3
/hour in this example must be scaled. This is
achieved by multiplying the totaliser factor, 1.0 in this example, by 60 x 60 to
get flow in units of flow/second.
For the Totaliser to count every 100 m3, the Totaliser Factor (P530/P532)
must be set to 3600 (1 x 60 x 60) and the Totaliser Units (P531/P533) must be
set to m
3
.
The 3490 Series Control Unit will then add 1 to the Totaliser Count (D828 /
D829) for every 100 cubic metres that flows. The Totaliser Count will be
automatically displayed in m
3
by setting the Totaliser Units.
Figure 4-43 on page 4-71 shows how the "Totaliser" Wizard can be used to
set-up this totalising example. It is assumed the PV value is a flow rate in units
of cubic metres per hour, which can be set-up using the "Duty" Wizard.
In addition, for this example:
•
Relay 4 (RL4) will be a Totaliser relay and output a 200 millisecond pulse
(P534) for every 100 m
3
added to the Totaliser Count.
(To set-up this manually, see “Relays“ on page 4-40.)
• No Sampler relay is required.
• The Totaliser will freeze immediately when any digital input is active i.e.
when the voltage-free contact is closed.
(To set-up this manually, see “Digital Inputs IN1 and IN2“ on page 4-34.)