56 tinb29e1-c (2019-10) VGC083A_B.om
When the analog output is setup, as described in section 6.5.6, for IG LINEAR, the
analog output voltage represents the pressure measured by the IG for nitrogen/air
only. The Linear analog output type provides a 0-10 V (dc) output signal that has a
direct linear relationship to the displayed pressure measured by the ion gauge only.
This selection covers 3 decades of pressure change. For example, if ANALOG
OUT 1 is programmed for IG LINEAR and the maximum pressure for AOUT LIN 1
selected is 1.00E-03 Torr, then the instrument provides a 10 volt analog output sig-
nal when pressure as measured by IG is at 1.00E-03 Torr. Furthermore, the mini-
mum pressure is automatically set to 1.00E-06 Torr, with a corresponding minimum
voltage output of 0.01 volts.
Constructing a table of these parameters may be useful in documenting the re-
lationship of displayed pressure (measured by the IG) to the analog output voltage.
The following table is representative of a typical setup where the IG may be used in
a limited range of pressure measurement where a direct linear relationship exists
between the displayed pressure (mantissa) and the analog output signal.
Linear Analog Output Voltage - volts
Measured (Displayed) Pressure - Torr
If your application requires the analog output voltage to cover a pressure range
exceeding three decades, then consider using a log-linear analog output type for
the IG.
The information discussed above regarding the Linear IG analog output applies
only to N2 / air. If you are using a gas other than N
2
/ air, refer to section 8.3.1.
Apply the Gas Correction Factor by dividing the pressure derived (from using the
Linear IG output discussed above) by the specific Gas Correction Factor to obtain
the true pressure of the specific gas in your vacuum chamber.
Notes: The output voltage will switch to above +11 V (dc) under the following
conditions:
1) The IG sensor is turned off or any IG fault condition.
2) The pressure exceeds 1.00 × 10
-3
Torr at 100 µA emission current,
5.00 × 10
-4
Torr at 4 mA emission current, 1.00 × 10
-4
Torr at 10 mA emission
current for BAG05x series ion gauges.
When the analog output is setup, as described in section 6.5.6, for CG1 1 – 8 V or
CG2 1 – 8 V, the analog output voltage represents the pressure measured by CG1
or CG2 for nitrogen/air only. Refer to section 8.3.3.1 if you are using a gas other
than nitrogen/air.
Analog output: Convection Gauge Log-linear 1 to 8 V (dc), 1 V per decade
A) The log-linear output signal and pressure are related by the following formulas
when units of measurement is in Torr and mbar:
P = 10
(volts - 5)
V = log
10
(P) + 5
Where P is the pressure in Torr or mbar, and V is the output signal in volts.
The output voltage is 1 V when pressure is at 1.00E-04 Torr.
The output voltage is 8 V when pressure is at 1.00E+03 Torr.
B) The log-linear output signal and pressure are related by the following formulas
when units of measurement is in pascals:
P = 10
(volts - 3)
V = log
10
(P) + 3
Where P is the pressure in pascals, and V is the output signal in volts.
Notes: An analog output of above +11 volts indicates a faulty convection
gauge or unplugged gauge cable.
7.6 Analog Output for IG
LINEAR (Nitrogen / Air
7.7 Analog Output for CG1
or CG2 1 - 8 V (Nitrogen
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