ASP STERRAD 100, Service Manual, Page: 179 / 309

Introduction
This chapter details the radio frequency (RF) subsystem. The sections in
this chapter briefly describe the functions of the RF subsystem and the
product certification. The RF subsystem has no specific calibration
procedures, nor does it have a complicated removal procedure.
Different RF Configurations
The STERRAD
®
100 system is currently in the
Block 2
and STERRAD
100 S System phase. These versions of the STERRAD 100 Sterilizer is
slightly different, in appearance only, from the Block 1.8 STERRAD 100
System. The calibration differences are noted in the text.
When you see the STERRAD icon next to the text, as with the paragraph
above, that is the symbol for a configuration other than Block 1.8.
RF Theory of Operation
The radio frequency (RF) subsystem comprises the upper enclosure at
the rear, right side of the STERRAD 100 Sterilizer (called the RF
generator), the RF match module that connects it to the process
chamber, and the RF power cable that joins the two. The generator
contains an amplifier and a switching power supply.
The RF generator, turned on and off by signals from the control
subsystem, generates a frequency of 13.56 MHz at a power of 400 Watts
nominal, 365 W minimum. This power is leveled using a closed loop feed
back circuit that detects and compensates for variations in load
impedance. The amplifier receives input power from an adjustable 750 W
AC/DC, switch-mode power supply. The amplifier efficiency is greater
than 75% into a 50 ohm load. The RF-amplifier features an automatic
self-protection circuit for high VSWR conditions, a thermal overload trip
and buffered outputs representing delivered and reflected power.
The RF power system interfaces with the STERRAD 100 Sterilizer
through two connectors. These are an AC input plug and a 15 pin
subminiature D control connector. The output of the RF Enclosure and
the input to the matching network both use a BNC female bulkhead
connector. The output of the matching network is connected to the
STERRAD 100 Sterilizer chamber via a copper rod, drilled and tapped for
an M3 fastener. The RF Match is grounded to the chamber by trapping it
between nuts on a 3/8” NPT conduit welded to the chamber.
Radio Frequency (RF) Subsystem Introduction
10-2 STERRAD® 100 Sterilizer ASP Service Guide rev. D