INFICON PLO-10i Phase Lock Oscillator - Manual (Page 47)

PLO-10 PHASE LOCK OSCILLATOR
CRYSTALS, HOLDERS AND FLOW CELL 7-13
♦ Always act fast in the event that liquids or chemicals have entered the crystal cavity
in the holder. Immediately clean the holder using the following procedure.
o
Remove the crystal to expose the crystal cavity.
o
Remove both Pogo® contact pins from their sockets. Use a pair of
tweezers (or gloved fingernail), grab the Pogo® head firmly and pull it
straight out of its socket.
o
Rinse the holder, the crystal cavity and the Pogo® sockets generously with
deionized water to remove all traces of chemicals and thoroughly blow-
dry the whole holder using filtered air. Ensure all liquids that may have
been trapped inside the sockets are removed.
o
Generously rinse the Pogo® contact pins with deionized water,
occasionally squeeze the pins to push out any liquids that may have been
trapped inside the pins. Thoroughly blow-dry the pins using filtered air.
o
Install the Pogo® pins back into their sockets. Use the tip of a pair of
tweezers and push down on each Pogo® pins to verify their deflection.
7.3.3 CONSIDERATIONS FOR BUILDING YOUR OWN HOLDER
You MUST consider the following aspects when building your own crystal holder.
The holder must be designed so that when a crystal is installed, its front electrode
(sensing electrode) is connected to the housing (shell) of the SMB Crystal Connector on
the PLO- 10; and the rear electrode is connected to the center pin of the SMB Crystal
Connector.
The crystal should be clamped, as close as possible, to the edge of the crystal to avoid
damping of the crystal’s oscillations.
The holder clamping mechanism should have a positive stop to avoid excessive clamping
force on the crystal.
If the crystal is to be used in a conductive fluid or conductive gas, the rear electrode must
be sealed from the conductive environment to avoid an electrical short between the
electrodes. The electrodes should be designed so the rear electrode and the electrodes
contacts can be sealed. Only the front electrode should be exposed.
The connecting cable must be coaxial all the way, from SMB on the PLO-10, on up to the
crystal. The shield of the coaxial must connect to the front electrode and the center
conductor must connect to the rear electrode of the crystal. In addition, the coaxial cable
must be free of kinks, knots, etc. to avoid unbalanced capacitance in the cable. Note that a
one-foot of well balance RG174A/U coaxial cable has approximately 29 picofarads.
The total capacitance of the crystal, the crystal holder and the cable must be within the
PLO-10’s capacitance compensation limits (between 40 and 200 pfd).
7.4 FLOW CELL
The FC-550 Flow Cell is designed to be used with any of INFICON's 100 series crystal
holders. The FC-550 is made from Kynar®. The cell has two stainless steel inlet and