MKS 907 Series, Инструкция по эксплуатации

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5 Operation
25
Series 907 Analog Convection Transducer
Instruction Manual - #109070001
5.5.1 Nitrogen Equivalent Pressure and Voltage
The thermal loss from a heated sensor element is a function of the transporting gas. See Section 5.3,
Theory of Operation. Since the 907 Transducer is such a sensor, the voltage output depends upon
the gas measured.
When used with gases other than nitrogen, the 907 Transducer reads in nitrogen equivalent
pressure. For example, when the 907 Transducer is set up to read pressure for nitrogen but is used
with the gases helium or argon, use the data for helium and argon in Figure 5-2 or Figure 5-3 to
convert nitrogen equivalent pressure to true pressure.
1. Locate the indicated pressure on the pressure axis of the graph. Locate the point at which a
vertical line from this point intercepts the curve for nitrogen.
2. Locate the point at which a horizontal line from the point on the nitrogen curve intercepts the
helium or argon curve.
3. Locate the point at which a vertical line from the helium or argon curve intercepts the pressure
axis. This point corresponds to the true pressure for helium or argon.
5.5.2 Calibrating for Gases Not Shown in the Graph or Table
To determine the voltage/pressure relationship for gases which are not shown in the graph or table,
you might need to calibrate the 907 Transducer for this gas. This calibration requires a gas type
independent gauge such as a capacitance manometer to act as the calibration standard. A curve
like that of Figure 5-3
can be generated.
5.5.3 Calibrating for Other Gases
To determine the voltage/pressure relationship for a gas which is not shown in the graph or table,
you need to calibrate the 907 with it. This requires a gas independent sensor, such as a capacitance
manometer, to act as the calibration standard. A curve can then be generated.
The Series 907 Transducer is not intended to be calibrated for direct pressure readings of gases other
than air or nitrogen. The calibration is intended only to match the air/nitrogen curve of the sensor.
The nitrogen equivalent pressures of some gases can exceed
the measuring capabilities of the 907. For example, a true
pressure of 20.0 Torr of helium is equivalent to a nitrogen
equivalent pressure of several thousand Torr. The 907 is not
capable of measuring this pressure of helium.