..
This procedure uses a conventional Volt-Ohm Meter (VOM) and Resistor (10 ohm, 10
watt)
1.
With the gauge controller turned off, test for both DC and AC voltages between
the metal parts of the vacuum chamber and the gauge controller chassis.
2.
If no voltages exist, measure resistance. The resistance should not exceed 2
ohms. Two ohms, or less, implies commonality of these grounds that should pre
vent the plasma from creating a dangerous voltage between them. This test does
not prove that either connection is earth ground, only that they are the same.
If more than 2 ohms is indicated, check with your electrician.
3.
If AC or DC voltages exist and are less than 10 volts, shunt the meter with a
10 ohm, 10 watt resistor. Repeat the voltage measurement. With the shunt in
place across the meter, if the voltage remains at 83% or more of the unshunted
value, commonality of the grounds is implied. Repeat the measurements several
times to be sure that the voltage ratio is not changing with time. If
Voltage (shunted) = .83 or more,
Voltage (unshunted)
this should prevent the plasma from creating a dangerous voltage between these
grounds. If more than 10 volts exists between grounds, check with your
electrician.
.
4.
If the voltage change in #3 is greater than 17% due to the placement of the
shunt, it complicates the measurement. The commonality of the grounds may be
satisfactory and the coupling poor, or the commonality could be poor! Your
electrician should be asked to check the electrical continuity between these
two ground systems.
01
Electric Power
The line power supplied the Series 270 controller should be one of the following:
I 00V with a 1.25 amp fuse
I 15V with a 1.25 amp fuse
230V with a .5 amp fuse
50 - 60 Hz single phase. Voltage selection switches, as shown in Fig. 3-1, are located
inside the instrument next to the power transformer and must be set to correspond to
the available supply voltage. Check to see that the power switch is turned to off.
Connect the power cable to the controller and to an appropriate source of A.C. power.
Use only a three wire grounded receptacle.
3-2
