Flow Signal Output Readings; Swamping Condition - Omega FMA 5400A User Manual

FMA Series Max. Flow 10, 50 and 100 L/min:
CAUTION: If the valve is left in the AUTO (control) or OPEN (PURGE)
mode for an extended period of time, it may become warm or even hot
to the touch. Use care in avoiding direct contact with the valve during
operation.
Do not run FMA Series Max. Flow 10, 50 and 100 L/min models for extended peri-
ods of time with the valve in AUTO or PURGE mode without the flow of gas
through the transducer. Doing so may result in up to 2% f.s. shift in calibration.
5.2

Flow Signal Output Readings

The flow signal output can be viewed on the LCD display, remote panel meter, dig-
ital multimeter, or other display device connected as shown in figure 2.1.
If an LCD display has been ordered with the FMA 5400A/5500A, the observed
reading is in direct engineering units, for example, 0 to 10 sccm or 0 to 100 slpm
(0 to 100% indication is optional). Engineering units for a specific FMA
5400A/5500A are shown on the flow transducer's front label.
Analog output flow signals of 0 to 5 VDC and 4 to 20 mA are available at the
appropriate pins of the 15-pin "D" connector at the side of the FMA 5400A/5500A
transducer (see Figure 2-1).
Meter signal output is linearly proportional to the mass molecular flow rate of the
gas being metered. The full scale range and gas for which your meter has been
calibrated are shown on the flow transducer's front label.
Default calibration is performed for 0 to 5 VDC input/output signal. If 4-20 mA out-
put signal is used for flow indication on the FMA 5400A/5500A, which was cali-
brated against 0 to 5 VDC input signal, the accuracy of the actual flow rate will be
in the specified range (+1.0% FMA 5400A/5500A 17, 37, 47. +1.5% FMA
5400A/5500A 57, 67, 77) of full scale, but the total uncertainty of the output read-
ing may be in the range of +2.5% of full scale. Optional calibration for 4-20 mA
output signal is available upon request at time of order.
For optional RS232 or RS485 IEEE488 interfaces please contact OMEGA
5.3

Swamping Condition

If a flow of more than 10% above the maximum flow rate of the Mass Flow Controller
is taking place, a temporary condition known as "swamping" may occur. Readings
of a "swamped" meter cannot be assumed to be either accurate or linear. Flow must
be restored to below 110% of maximum meter range. Once flow rates are lowered
to within calibrated range, the swamping condition will end. Operation of the meter
above 110% of maximum calibrated flow may increase recovery time.
12
®
.