16.7.4 Operational Test
1. Plug in the MFC with the gas off and the MFC turned on.
2. Allow the MFC to warm-up for 60 minutes.
3. Note what zero reading is displayed.
4. T
urn off the MFC, using either manual (pin J, Input=0 VDC) or automatic shutoff (zero
setpoint of models with Auto Shutoff feature). Verify that no gas is flowing when the
MFC is off. This is critical to the accurate and repeatable operation of the automatic
zero feature.
Celerity suggests that positive isolation valves be installed upstream and downstream of the
MFC to ensure no gas flow during Auto-Zero operation cycle. If the MFC is being used in a
vacuum process we recommend that zeroing take place under vacuum conditions to better
ensure that there is no flow.
If the MFC is installed in the vertical position, the gas should either be evacuated or the
pr
essure reduced to atmosphere. Celerity recommends this because, some high density
gases exhibit a thermal siphon effect within the MFC during standby. Thermal siphon
produces internal recirculating flow within mass flow controllers due to heating of the gas.
This effect will cause the Auto-Zero to offset in error. Current Celerity MFCs with the new
sensor will not exhibit this offset
5. Wait 3 minutes to allow the Auto-Zero to complete the zeroing process.
6. Confirm that the reading is zero (±0.2% of full scale).
16.7.5 Auto-Zero Specifications
Performance
Accuracy..........................±0.2% of full scale
Time Requirement
Warm-Up.........................60 minutes
Auto-Zer
o stabilization......2 min delay between turn on and Auto-Zero function
Auto-Zero operation..........continuous comparative cycle for 30-60 seconds minimum
after valve off or until the MFC is turned on
Operating Period.............. after MFC cutoff and 90 sec. delay continuous operation until
the MFC is turned on
Minimum Operating T
ime..2 to 3 minutes depending on of
fset of tr
ue zer
o
Operating Limits...............±4-5% of full scale
Auto-Zer
o Alar
m...............
Indicates Auto-Zer
o at operating limits.
Transistor close: Pin I B/C
Ambient T
emp. Range......
0
°
-50
°C (32°-122°F)
Dimensions......................1.6" x 1.1" x 0.1"
31
©2005 Celerity
, Inc.
#199-001-0006 REV
.F 4/05
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
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