INFICON RQCM - Quartz Crystal Microbalance Research System - Manual (Page 15)

RQCM – RESEARCH QUARTZ CRYSTAL MICROBALANCE
GENERAL DESCRIPTION 1-1
1 GENERAL DESCRIPTION
The RQCM is designed for many types of research applications where QCM (Quartz
Crystal Microbalance) measurement is desired. Included with each instrument is a
Windows™ based software package that allows the user to configure the RQCM, setup
multiple experiments, log data with real-time graphing and review results from previous
experiments.
The QCM portion of this system accurately measures crystal frequency and crystal
resistance for up to three crystals simultaneously. The software uses this data to derive
various physical parameters of the deposited film and/or the liquid or gas environment at
the surface of the crystal. The heart of the system is a high performance phase lock
oscillator (PLO) circuit that provides superior measurement stability over a wide
frequency range (3.8 to 6.06 MHz, or 5.1 to 10 MHz). The circuit incorporates adjustable
crystal capacitance cancellation reducing error caused by the parasitic capacitance of the
crystal, cable and fixture. Capacitance cancellation is essential for accurate measurements
of lossy (soft) films.
Data collection from external sources is accomplished with an optional Data Acquisition
Card, which provides three temperature inputs (RTD, Thermocouple and Thermistor) as
well as five scalable analog inputs. For example, you can use the analog inputs to acquire
potential and current data from a potentiostat during a cyclic voltammogram. The
RQCM allows you to combine this data with the mass data of the QCM to create a graph
of mass and current versus potential.
Control of external instruments and peripheral devices is accomplished with an optional
input/output card. Each remote I/O card provides eight remote inputs and eight relay
outputs. The functions of the inputs and outputs are defined in the RQCM’s software
with some typical uses including the control of pumps, heaters, valves, instrument
initiation, etc.
1.1 FEATURES
1.1.1 VERY WIDE FREQUENCY RANGE
The RQCM supports a wide frequency range from 3.8 to over 6 MHz. It will support
both 5 and 6 MHz crystals; and with a low limit of 3.8 MHz it will support 1.2 MHz of
frequency shift on a 5MHz crystal. A frequency range of 5.1 to over 10 MHz is also
available.
1.1.2 SUPPORT FOR VERY LOW Q, HIGHLY DAMPED, CRYSTALS
The RQCM will accurately measure crystals with resistances up to 5 KΩ. In most cases
it will maintain lock up to a resistance of 10 KΩ or more. It will support crystal
oscillation in highly viscous solutions of more than 88% glycol in water.
1.1.3 DIRECT REAL-TIME MEASUREMENTS OF CRYSTAL FREQUENCY, MASS,
AND RESISTANCE
The RQCM accurately measures crystal frequency, mass, and resistance. The
software uses this data to derive various physical parameters of the deposited film
or media at the surface of the crystal.