Functions
7.4 Function Group Measuring Functions
SITRANS F M TRANSMAG 2
46
Operating Instructions, 11/2009, A5E00102775-07
0
b
a
-1
+1
①
Reverse
②
Forwards
③
Flow in % of range
Figure 7-3
Hysteresis flow direction
1.
Hysteresis (3.1.5.3). The limit values (menu items 3.1.5.1 and 3.1.5.2) can have a
hysteresis added to prevent "fluttering" of the switching output.
This setting is made in % of the set full scale value in the menu item 3.1.5.3 "Hysteresis".
If, for example, the hysteresis is 1 %, the relay contact does not switch until a flow of -1%
of the full scale value and returns to the original position at a flow of +1% of the full scale
value.
Table 7- 2
Switching status of the relay for selected signal type
- Contact closes:
a →
Relay contact closed
b →
Relay contact open
- Contact opens:
a →
Relay contact open
b →
Relay contact closed
● Low flow cut, menu item 3.1.6
This parameter determines the switching point for low flow cut-off. The low flow cut
prevents flow being measured in the lower range (e.g. fluctuating liquid columns at a
standstill). The low flow cut-off affects: display, totalizers, analog output and pulse
frequency output as well as HART and PROFIBUS communication.
– In devices with HART communication, the value of the low flow is related percentage-
wise to the upper range value (menu item 3.1.2).
– In devices with PROFIBUS communication, the absolute value must be entered in the
selected unit of flow (menu item 3.1.1).
● Filter time constant, menu item 3.1.7.1
The jump response can be suppressed in this menu item. This may be necessary
depending on the application, for example in the case of fast changing flows to keep the
display value or analog value stable.
● Noise Suppress, menu item 3.1.7.3
This function serves to eliminate temporary, application-related interference within a fixed
time frame.
Every measured value within a measuring pulse is compared with the previously
determined value. If it is outside the tolerance band set under menu item 3.1.7.3 (the