A micro balance or ultra-microbalance can deliver the highest precision of all lab balances. Microbalances offer a capacity of up to Ultra microbalances offer an incredible full resolution of 61 million digits, with a capacity of 6. The XPE micro-analytical balances deliver the highest capacity, coupled with the lowest possible minimum weight. This enables dosing of very small amounts directly into a "large" tare containers.
A micro balance consists of two components - one containing the electronics and the other, the precise mechanical measuring cell.
This separation eliminates the effects of temperature and the influence it has on the performance of your micro balance scale.
This increases the weighing stability and enables an outstanding level of performance and accuracy. Microbalances and ultra microbalances are frequently used in product testing and quality assurance labs, as well as chemistry labs and mining to measure small amounts of powders and minerals. Medical device research might also employ a micro balance to check uniformity in critical components. Micro balance applications include: particulate matter filter weighing, pipette calibration, analysis of pesticides, and stent weighing.
Ultra micro balance applications include: particulate matter filter weighing, ashing or incineration, drying, measurement of coatings, and checking spillage quantities. Every measurement on any balance is subject to uncertainty - understanding this uncertainty is key to ensuring accurate results and the avoidance of errors. When weighing small samples on a microbalance, uncertainty is almost entirely due to repeatability i. It is not the readability that determines the accuracy of a weighing instrument, but rather its repeatability, or depending on it, its minimum weight capability.
A micro balance is an extremely sensitive instrument — the slightest disturbance caused by environmental influences or user interaction can significantly affect measurement stability. All possible sources of vibrations should be avoided when using a micro balance. Microbalances are highly susceptible to air currents, dust, and fluctuations in temperature, and should only be used where ambient temperature and humidity are maintained at a stable level — away from vents, windows, and doors.
Ideally the balance should be set-up on a solid workbench - preferably a dedicated weighing table that can remain optimised for micro balance use, free from draughts or high traffic. When a micro balance is first connected to the power supply or switched on, a minimum warm-up time of 6 hours is recommended for ambient temperature adjustment. When using the micro balance, be sure to minimize convection flows inside the weighing chamber, which can negatively impact results.
Only handle samples with tweezers, and allow acclimatisation to room temperature. When placing the sample onto the micro balance, the door should be opened to a minimum degree, for as short a time as possible. Always wear gloves while working with microbalances — fingerprints and oil from hands affect results. To start a weighing operation, open the door and place a container on the pan using tweezers. Close the door and allow the value to stabilize. Tare the micro balance. To avoid spills in the balance remove the container or weighing boat, dose the sample outside the weighing chamber, and place the sample on the weighing pan.
Close the door and wait for stability. Record the net weight or repeat the procedure until desired weight is reached. A micro balance is highly sensitive to movement - do not touch the bench while waiting for the balance to stabilize. Clean the balance, tools and workspace after each use. Quartz Crystal Microbalance QCM is an extremely sensitive mass balance that measures nanogram to microgram level changes in mass per unit area.
The heart of the technology is a quartz disc. Quartz is a piezoelectric material that can be made to oscillate at a defined frequency by applying an appropriate voltage usually via metal electrodes. The frequency of oscillation can be affected by the addition or removal of small amounts of mass onto the electrode surface.
For 60 years, QCM has been used under vacuum and gas phase, and about 40 years ago this technique was shown to be applicable in liquid media, as well.
Molecular adsorption via the vacuum or gas phase typically results in rigid films that are fully coupled to the oscillation of the electrode surface. Hence, the change in mass of such films is linearly related to the change in the oscillation frequency which is defined by a well-known equation called the Sauerbrey Equation.
The QCM can provide useful information on the amount of mass deposited and the rate of deposition or removal of such films by monitoring the real-time change in frequency. Adsorption can produce soft, or viscoelastic films and the resulting layer may not fully couple to the oscillating crystal. This can lead to dampening, or energy loss, of the oscillation.
The mass of such films cannot be determined accurately by measuring the frequency change alone. QCM-D also provides real-time information on the viscoelastic properties of the adsorbed film, such as viscosity, elasticity, and density.
The maximum film thickness that can be measured varies from several hundred nanometers to a few microns, depending on the rigidity of the film. QCM-D has a wide range of applications in various fields of science. Some examples include: kinetics of molecular interactions e. Piezoelectricity is defined as the generation of electricity in response to the mechanical deformation caused by mechanical stress or as the generation of physical deformation on the application of electricity in such crystals.
The French physicists Pierre and Jacques Curie discovered this effect in when they demonstrated that salt crystals could produce electricity when deformed along certain crystallographic orientations. Quartz, besides being piezoelectric, also possesses a unique combination of properties that make it an ideal candidate for ultrasensitive devices.
It is found in abundance in nature, and it is easy to grow and process. To fabricate quartz crystal resonators, wafers are cut from the bulk quartz crystal at specific orientations with respect to the crystallographic axis. When the corresponding alternating current is applied to the quartz disc, it will oscillate at its resonance frequency. The resonance frequencies are typically on the order of MHz and inversely proportional to the crystal thickness.
The effects of temperature on frequency for various angle cuts are well known and documented. The frequency change in QCMs can be measured with a resolution of 1 Hz or less on crystals with a fundamental resonance frequency in the MHz range.
Because of its high stability as a resonator, quartz crystals were successfully incorporated, in the early s, as components in various devices such as electronic filters, frequency control devices, and ultrasonic transducers. Equation 1, typically referred to as the Sauerbrey equation, constitutes the basic principle of QCM technology. This means that the addition of The frequency of 5 MHz quartz can be easily measured with a precision of 0.
Sauerbrey developed Equation 1 assuming that a small mass added to the crystal can be treated as an equivalent change in the mass of the quartz crystal itself. This means that the equation is only valid when the added mass is rigidly adsorbed on the quartz surface with no slip. Sauerbrey continued his investigation of the mass sensing properties of the QCM and later demonstrated that the crystal vibration is restricted to the area where the electrodes overlap as illustrated in Figure 1d.
This area of vibration is called the active area of the crystal. This differential mass sensitivity of the quartz surface area constitutes another limitation for the Sauerbrey equation, namely, that the mass must be evenly distributed over the active area.
In summary, the Sauerbrey equation is valid under the following three conditions: i the added mass is small compared to the mass of the crystal itself, ii the added mass is rigidly adsorbed, and iii the mass is evenly distributed over the active area of the crystal. This equation has been used and is still being used in several industries for monitoring the rate and thickness of metal deposition under the vacuum or gas phase. The development of a QCM that could be operated in liquid media was the next step in advancing its applications.
However, the task posed several challenges to early researchers. With the invention of liquid media QCM, 20 the applications for QCM extended widely in the fields of biology, biotechnology, polymers, lipids, proteins, electrochemistry, environmental studies, nanoparticles, etc.
Such viscoelastic films cause dissipation of oscillation energy due to mechanical losses in the flexible mass. The linear relationship between the frequency and mass, as defined by Sauerbrey, fails for viscoelastic films. Hence, it is important to take dissipation into account when quantifying viscoelastic mass. When a piezoelectric quartz crystal resonates, both electrical current and mass oscillate simultaneously. Therefore, quartz can be represented by either its equivalent electrical circuit Figure 3a or a mechanical circuit model Figure 3b.
The two models can be compared as follows: L 1 represents the oscillating mass, C 1 represents its elasticity, and R 1 represents the energy losses in the system.
C 0 is the shunt capacitance due to the overlap of the electrode on the crystal surface. Expertise Library. Literature: White Papers, Guides, Brochures. Technical Documentation.
On Demand Webinars. Live Events. Live Webinars. Management Investor Relations. Service Finder Videos. Select Country. Brochure: XPR Microbalances. To make the most of your valuable resources, XPR microbalances and ultra-microbalances deliver a unique level of precision with exceptionally low mini Installation Instructions.
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