Fluid Components International MT91 Manual Operation - Manual (Page 11)

CHAPTER 3 - OPERATION FLUID COMPONENTS INTL
Doc. No. 003185 Rev. B 3 - 11 Model MT91 Multipoint Flowmeter
3. Select from the following options:
1=View Mode - this can be used to verify current setup;
2=Flow - select this if a switch point is going to be set;
3=Temperature - select this if a switch point is going to be set;
4=System Status - this relay is used to notify the customer when the "System OK" is no longer displayed;
5=Zero Test - this is used with the Calibration Testing discussed in the next section. During the zero test phase
(4mA), the Zero Test relay is closed.
6=Span Test - this is used with the Calibration Testing discussed in the next section. During the full scale test
phase (20mA), the Span Test relay is closed.
During the mid range test phase (12mA), both the Zero and Span Test Relays are closed.
If assigned, the test/status relays are ready to be connected to customer equipment.
When assigned to flow or temperature, relays 1 and 2 are affiliated directly with analog output channels 1 and 2,
respectively. For this reason, relay 1 can only be assigned as a flow or temperature switch point when analog output
channel 1 is assigned as a flow output for flow switch or temperature output for temperature switch. The same
applies to relay 2.
Switch points are not appropriate for the test/status parameters since they are already discrete signals. Relays 1 and 2
can be assigned as switch points or as test/status parameters. As switch points, when the signal level crosses into a
specified range, the relay will activate. Hysteresis can be set to prevent the relay from chattering at the switch point
threshold.
The user can choose from four sets of switch point ranges. These are referred to as above, below, inside, and
outside. With hysteresis, the relay will deactivate at a different threshold than at which it activates. Figure 3-7
illustrates the four switch point ranges with arbitrary hysteresis assigned.
Flow
or
Temperature
A b o v e
OFF
ON
Below
OFF
ON
Outside
O N OFF
Inside
ON O F F
Switch point
Deactivation
}
Hysterisis
C00225-1
Figure 3-7. Relay Switch Points Schemes
Ø To set the switch points and hysteresis:
1. Go to menu level 2.2.3.2 (Setup Þ Outputs Þ Relays Þ Switch Points). Relays 1 or 2 must be in a flow or
temperature mode. See above section.
2. Select 1=Rly #1 or 2=Rly #2. To view the current switch point settings select 1=View Sw. Pt. To set the switch
point follow one of the procedures below.
a. Select 2=Above to activate the relay above a switch point value. Enter a numeric value for the upper
limit of the switch point. Press ENTR to accept the value.
b. Select 3=Below to activate the relay below a switch point value. Enter a numeric value for the lower
limit of the switch point. Press ENTR to accept the value.
c. Select 4=Inside to activate the relay if flow or temperature values approach the switch point from the
outside going inside. Enter a numeric value for the upper limit of the switch point range. Press ENTR
to accept the value. Enter a numeric value for the lower limit of the switch point range. Press ENTR to
accept the value.