Ulvac GI-M2 - 9 Functions; Setting of Sensitivity; Details of Sensitivity Set

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9. FUNCTIONS
9.1. Setting of Sensitivity
9.1.1. Setting of sensitivity
The ion gauge ionizes gas molecules, measures the ion current produced and converts
it into a pressure. Since the ratio of ionization varies with the type of gas molecules,
the amount of ions produced changes under the same pressure. Its correction is made
by the sensitivity setting.
9.1.2. Setting of sensitivity
The sensitivity setting value is entered in the form of □.□□× 10-□.
Sensitivity can be entered from the front panel or through the communication (RS-232C).
The numerical value that can set as follows.
GI-M2
GI-D7
GI-N8
Setting
range
6.00×10
-1
~
6.00×10
-3
7.47×10
-1
~
1.66×10
-2
2.00×10
-0
~
2.00×10
-2
When the input of an invalid value, it is converted into the nearest effective value. [Err.
12] is displayed on the segment indicator only in the front panel setting.
Sensitivity can be entered from the front panel or through the communication (RS-232C).
The finally set value is saved.
9.1.3. Details of sensitivity set values
"Sensitivity" referred to here is the total sensitivity obtained by multiplying the
sensitivity constant (K) of the ULVAC sensor head (M type) for nitrogen by the relative
sensitivity (Srj) for various types of gases, where the sensitivity for nitrogen is given as
1. This gauge is available with the N2 mode, Ar mode, and OTHER mode as standard.
The each sensitivity set value (Srj(N
2
))of ULVAC sensor head as follows.
GI-M2
GI-D7
GI-N8
Sensitivity set
value of ULVAC
sensor head
Srj(N2)
0.06 Pa
－１
0.0827 Pa
－１
0.153 Pa
－１
In case of GI-M2 as follows
Ｎ
２
： ６．００×１０
－２
Ｐａ
－１
＝ Srj(N
2
)
Ａｒ ： ８．０４×１０
－２
Ｐａ
－１
≒ Srj(N
2
) × Ｓｒｊ ＝ ０．０６×１．３４
ＯＴＨＥＲ ： Srj(N
2
) × Ｓｒｊ＝０．０６ × Ｓｒｊ Ｐａ
－１
OTHER mode is used when measuring the pressure in a vacuum chamber in which gas
other than nitrogen gas (nearly equivalent to air) and argon gas are the major
components.
To use this mode, obtain the relative sensitivity (Srj) of the gas to be measured from
Table. 13-1, multiply it by sensitivity constant Srj(N
2
) of the sensor head and enter
the product.
Notice:
Relative sensitivity is the value when the atmospheric gas to be measured is
100%.
If the partial pressure percentage of the atmospheric gas differs, error will result.
If the sensitivity of individual sensor heads is known in the measurement of
nitrogen gas, the relative sensitivity is given as "1.00", and it is multiplied by the
sensitivity of individual sensor; thereby more accurate measurement can be made
by setting in the same manner as above.