The balance is used to measure the mass of a body or substance or also the weight of them, since between mass and weight there is a well defined relationship. In the laboratory, the balance is used to perform quality control activities -with devices such as pipettes-, to prepare mixtures of components in predefined proportions and to determine specific densities or weights. To install and use a balance successfully, the following is required:
• Have an environment that does not present air currents, sudden changes in temperature and that is free of dust.
• Have a perfectly leveled counter. A high inertia platform is ideal, isolated from the structures located in the vicinity, to reduce the effect of vibrations emitted by certain equipment such as centrifuges and refrigerators. It must have a sufficient area to install the balance and that auxiliary equipment with which it interacts in the weighing processes. Likewise, the space required by the interconnection cables, electrical current, connection to the information system, the printer, etc., must be provided.
• Avoid the installation of equipment that produces high magnetic fields or vibrations in the vicinity, such as centrifuges, electric motors, compressors and generators.
• Avoid being under the direct influence of air conditioning systems - air currents - and sunlight.
• Have an electrical outlet in good condition, equipped with a ground pole equipped with switches, which complies with the electrical regulations in force in the country or the laboratory.
Operation of the electronic balance
The operation of a modern electronic balance is clearly defined in the operation manual supplied by the manufacturers. In general, the following procedure must be followed:
• Allow the balance to balance its conditions with those of the environment where it is installed.
• Allow the scale to warm up before starting activities. Normally it is enough that it is connected to the electrical power system. Some manufacturers suggest that a period of time of at least 20 minutes be allowed to elapse, from the moment it is energized until the moment in which the use of it begins. Class I analytical balances require at least 2 hours before starting their use. 3. Verify that the balance is calibrated. Electronic scales usually have a factory calibrated, stored in memory, which can be used if no calibration masses are available. If calibration is required, calibrated masses must be available to carry out the procedure indicated by the manufacturer. The calibrated masses used must meet or exceed ASTM tolerances. As general information, a table showing the tolerances accepted for ASTM Class 1 masses is included below.
What should your maintenance routine be?
The balance is characterized by being a high precision instrument. For this reason, maintenance routines at the operator's expense are minimal and limited to the following daily activities:
• Clean the weighing pan so that it is free of dust or dirt. The cleaning is done with a piece of clean cloth that can be moistened with distilled water. If it is necessary to remove some stain, a mild detergent can be applied. You can also use a soft hair brush to remove particles or dust that have been deposited on the weighing pan.
• Externally and internally clean the weighing chamber. Verify that the glasses are free of dust.
• Verify that the adjustment mechanisms of the front door of the weighing chamber work properly.
Never lubricate a scale unless expressly indicated by the manufacturer. Any substance that interferes with the mechanisms of the balance delays its response or permanently alter the measurement.
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