MKS 146C - Page 236

Chapter Seven: Operation in Setup Mode Code 1: How To Select Pressure/Volt/Current
213
The high voltage (HU) selection only applies to cold cathodes (CC). The high voltage, which is
being applied to the cold cathode, is shown in the main display in Normal and Leakage Modes.
This display can be used for several purposes, such as a diagnostic aid. For example, if the cold
cathode is shorted, a very low voltage is displayed. If the pressure is very high (above 1 Torr),
there may be enough gas available to prevent any high voltage conduction, therefore a full high
voltage is applied to the cold cathode (and shown in the main display).
Note
If the HU (high voltage) selection is chosen for a hot cathode, then 0
(zero) is shown in the main display in Normal and Leakage Modes.
The Ion Current (IC) selection applies to both hot and cold cathodes. Ion current is sometimes
referred to as the
collector current
. This display shows the current that is present at the collector
inside an ion gauge.
The Emission Current (EC) selection only applies to hot cathodes (HC). The emission current is
maintained at 1 milliampere when the pressure is below 1 x 10
-4
Torr. At pressures higher than
1 x 10
-4
Torr, the emission current is maintained at 100 microamperes. This reduced emission
current level helps to extend the life of a hot cathode gauge.
Note
If the EC (Emission Current) selection is chosen for a cold cathode, a
0 (zero) is shown in the main display in Normal and Leakage Modes.
1. Repeatedly press the [
DISPLAY MODE
] key until the 146 unit is in Setup Mode.
The system responds by scrolling through modes.
2. Use the arrow keys to scroll to the
CODE
legend.
The system responds by causing the left display to blink.
3. Enter the number
1
and press the [
ENTER
] key.
The system responds by displaying the appropriate parameters for code 1, and causing
the main display to blink.
4. Select PrES or Volt in the main display (the default is pressure).
A. If the display is correct, then press the [
ENTER
] key.
B. If the display is not correct, press one of the arrow keys, then press the [
ENTER
]
key.
The system responds by accepting the parameter value.
Note
If PrES is selected, the right window becomes blank and the Code 1
function is finished.
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