Inficon IMM-200, Руководство по эксплуатации, Страница: 26 / 67

6 | Special Features INFICON
26 / 67 074-733-P1A IMM-200 Operating Manual
6 Special Features
6.1 Introduction
To enhance its performance and allow easier integration into a system having rotary
sensor heads, IMM-200 is equipped with special features. These special features are
explained further in the following subsections.
6.2 50 / 60 Hz Line Frequency
The AC Line Frequency configuration parameter is used to minimize measurement
system noise by identifying to IMM-200 the mains voltage line frequency. The
difference between 50 and 60 Hz line frequency has a small affect on the
measurement circuit timing. In most cases this is negligible. However in cases where
the material density and deposition rate are very low, setting this parameter value to
match the mains voltage line frequency optimizes IMM-200 measurements.
6.3 Start/Stop Measurement
The Start/Stop Measurement remote communications command indicates to IMM-200
to either start measuring frequency or to stop measuring frequency. The unit is placed
into idle when the stop measurement command is sent. This command is very useful
when using a rotary sensor head. Since IMM-200 does not control the indexing of the
rotary head, it has no way of knowing when a crystal switch is being performed.
Therefore, whenever a crystal switch is done, a crystal fail occurs after breaking
electrical contact during the crystal switch.
When the Stop Measurement command is activated, IMM-200 stops looking for the
crystal signal. The rotary head can then be indexed to the next position without a
crystal fail occurring. Once the rotary head is in the next position, the Start
Measurement command is given and the unit looks for the crystal signal. Once the
crystal frequency is acquired, IMM-200 resumes calculating the rate and thickness.
The thickness value begins incrementing from the point of the previous crystal's last
thickness value. The value used is the one recorded immediately prior to when the
Stop Measurement command was received by IMM-200.