MKS HPS 919 Series, Operation And Maintenance Manual

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Hot Cathode Ionization High Vacuum Senor System
Pin 13 – Turn on the degas. The front panel Degas switch must be set to
remote and either the front panel Filament switch is set to on or pin 10,
remote filament-enable, is connected to a TTL low voltage or ground.
If the filament turns off, degas will turn off automatically. To restart degas,
the filament must be restarted either with the front panel Filament switch or
through the Accessory connector.
To turn off degas, allow this remote degas-enable pin to rise to a TTL high
level or to be released from the TTL low voltage or ground so that the
Controller’s circuitry can pull it up to the TTL high level.
The Low Emission Current (LEC) monitor, pin 14, is a TTL compatible output
signal that indicates the emission current state. If the Series 919 Controller
detects LEC, the monitor will be at a TTL high level. The filament and degas
power will automatically be disabled to protect the system. LEC can indicate
operation at too high of a pressure, operation above the protection pressure,
or a broken filament.
Relay Inductive Loads and Arc Suppression
If the set point relays are used to switch inductive loads, e.g., solenoids,
relays, transformers, etc., the arcing of the relay contacts may interfere with
Controller operation or reduce relay contact life. Therefore an arc suppression
network, shown schematically below, is recommended. The values of the
capacitance C and the resistance R are calculated by the equations,
C = I
2
/(1 x 10
7
) and R = E/I
a
where,
C is in farads
R is in ohms
I is DC or AC
peak
load current in amperes
E is DC or AC
peak
source voltage in volts
a = 1 + (50/E) in volts
-1
.
Note that,
R
min
= 0.5 and C
min
= 1.0 x 10 -9 F.
Relay arc suppression
network
Ú
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