24
MANUAL P/N 316005 REV: B
NW16KF Flange Mount
The KF mounting system requires an O-ring and centering ring to be placed between the mating flanges. The
flanges are then held together with the aluminum flange clamp by tightening the wing nut. Maximum pressure
for this style mounting system is 1000 Torr absolute.
Other Mounting Options
The Convectron gauge is also available in several other mounting systems. These include Cajon
®
SS-4-
VCR
®
-1, SS-4-VCR-3, and SS-6-VCO
®
-1 fittings, 2-3/4 inch rotatable and non-rotatable CuSeal flanges,
1-5/16 inch non-rotatable CuSeal flange, and welded NW16 and NW25 SST flanges.
2.4 Convectron Gauge Operation
2.4.1 Reading Pressure
WARNING
If used without proper calibration or without reference to proper calibration tables, Convectron
gauges can supply misleading pressure indications. This can result in dangerous overpressure
conditions within the system. As supplied from the factory, the controller is designed to read
pressure for nitrogen. For use with any other gases, consult the gas type correction charts found
later in this section.
Convectron gauge pressures are indicated in the 316 display with two or three significant digits of resolution
above one millitorr and one significant digit in the 10
-4
Torr decade. The pressure is displayed in Torr/millitorr
(mbar/mbar x 10
-3
or pascal/pascal x 10
-3
) notation. That is, at pressures below one Torr, the display shows a
10
-3
exponent indicating millitorr while higher pressures display no exponent, indicating Torr.
Special Considerations For Use Below 10
-3
Torr
During a fast pumpdown from atmosphere, thermal effects will prevent the Convectron from tracking
pressure rapidly below 10
-3
Torr. After about 15 minutes, readings in the 10
-4
range will be valid and response
will be rapid. Calibration at vacuum can be performed at this time, or sooner if readings in the 10
-4
range are
not needed.
The 10
-4
Torr range is accurate to about 0.1 millitorr provided the instrument has been carefully zeroed at
vacuum. See Section 2.4 for vacuum and atmosphere calibration procedures. For accurate use in the 10
-4
Torr range, zeroing should be repeated frequently.
Use With Gases Other Than N
2
and Air
Before using the Convectron gauge to measure the pressure of other gases make certain the ATM
adjustment is correctly set for air. See Section 2.5.
It is important to understand that the indicated pressure on a Convectron gauge depends on the type of gas
in the gauge tube, and on the orientation of the gauge tube axis as well as on the gas pressure in the gauge
tube. Convectron gauges are supplied calibrated for N
2
within the accuracy of the instrument. With certain
safety precautions, the Convectron gauge can be used to measure pressure of other gases.
Convectron gauge tubes are thermal conductivity gauges of the Pirani type. These gauges transduce gas
pressure by measuring the heat loss from a heated sensor wire maintained at constant temperature. For
gases other than N
2
and air the heat loss is different at any given true pressure and thus the indicated
reading will be different.
