Omega FMA 1500 - Manual (Page 16)

age is a linear representation of 0 to 100% of the full scale mass flow rate.
Response time to set point changes are 1 second (FMA 1400 for ranges up to 10
L/min) and 2 seconds (FMA 1400 for ranges above 10 L/min) to within 2% of the
final flow over 25 to 100% of full scale.
On pin 6 of the FMA 1400 transducer is a regulated and constant +5VDC output
signal. This signal may be used in conjunction with a local set point potentiome-
ter for flow setting.
FIGURE 5-1, LOCAL SET POINT POTENTIOMETER CONNECTIONS
It is recommended that a potentiometer between 5K to 100K ohm and capable of
at least 10-turns or more for adjustment be used. Use the control potentiometer
to command the percentage of flow desired.
Alternatively, a variable 0 to 5VDC analog signal may be applied directly to the SET
POINT and COMMON connections of the FMA 1400 transducer (see Figure 2-1).
5.5 TTL, Valve OFF Control (FMA 1400)
It may, at times, be desirable to set the flow and maintain that setting while being
able to turn the flow control valve off and on again. This can be accomplished by
applying a (TTL compatible) high and low signal of +5 VDC and 0 VDC to pin 8,
on the 15-pin "D" connector. When 0 VDC (LOW) signal is applied, the solenoid
valve is not powered and therefore will remain normally closed. Conversely, a +5
VDC (HIGH) signal applied will allow the solenoid valve to remain active. The sole-
noid valve will remain active when the VALVE OFF pin remains "floating".
The simplest means for utilizing the VALVE OFF control feature, is to connect a
toggle switch between the COMMON and VALVE OFF pins of the FMA 1400
transducer. Toggling the switch on and off will allow for activating and deactivating
the solenoid valve.
5.6 Valve Test/Purge (FMA 1400)
At times, it may be necessary to purge the flow system with a neutralizing gas
such as pure dry nitrogen. The FMA 1400 transducer is capable of a full open con-
dition for the solenoid valve, regardless of set point conditions. For FMA 1400's
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