August 17, 2012 -- All balances are required to deliver precise and, above all, correct results. To ensure accuracy, users need to not only check that a balance’s metrological specifications are suitable, but also that they control all parameters that influence weighing when setting up and operating a balance. Temperature fluctuations, exposure to sunlight, benchtop vibration and leveling are only a few of the conditions that can distort weight measurements and that can be monitored by an advanced weighing instrument. Incorporating numerous functions for Advanced Pharma Compliance (APC), the new Sartorius Secura laboratory balance offers a new level of security in all weighing processes.
Checking whether a balance is level is an essential part of testing and controlling the accuracy of measuring equipment, and is a prerequisite for obtaining exact weights and related values. The opto-electronic LevelControl sensor has proved its efficacy for years in the Sartorius Cubis series of balances and is therefore also used in the new Secura balance. If this balance is not exactly level, the sensor triggers a red alert that is clearly displayed. Moreover, it blocks output of data over the interface port until the balance has been correctly leveled again to prevent uncertain weighing results from being stored and further processed (Fig. 1). Moreover, the LevelControl function simplifies the leveling procedure by showing sensor-controlled, easy-to-understand prompts on the display for user guidance. This enables users to effortlessly level the balance even when it is installed in a safety workbench or a safety weighing cabinet, without having to open the protective work chamber.
Automatic Calibration and Adjustment
Unstable ambient conditions, such as temperature fluctuations, have a substantial impact on the results of weight measurements. For this reason, a balance must be calibrated and adjusted at regular intervals and as soon as these environmental conditions change. The new Secura balance with its isoCAL function monitors whether a predefined temperature difference and/or a time limit is exceeded, and calibrates and, if necessary, adjusts the balance automatically using built-in weights (Fig. 2).
SQmin for Monitoring the USP Minimum Sample Weight
Every balance that is used in regulated areas, such as pharmaceutical laboratories, have to meet Food and Drug Administration, or FDA, requirements. For this reason, the minimum sample weight according to the United States Pharmacopeia, USP, must be determined at the site where a balance is set up, and all weight readouts may not go below this minimum. Even a high preload, such as a heavy tare container, does not change this minimum sample quantity permitted by the USP for a specific balance. For setting up a new balance, the Sartorius Services unit offers the option of determining this minimum sample weight on site and issuing the respective USP-compliant certificate. Once this weight has been entered, it will be constantly shown on the balance display, identified by SQmin (Fig. 3).
Fig. 3: The minimum sample weight requirement is met; the weight reading is within the tolerance range.
If a weight reading is below the minimum sample weight permitted, the display mode of this reading will change. The balance warns users by showing the SQmin weight in red and blocks the printout or transmission of an out-of-tolerance weight reading to a PC (Fig. 3). In other words, this value can no longer be output.
Fig. 4: The weight reading is below the minimum sample weight; the weight reading is out of tolerance.
Protection against Tampering
In especially sensitive areas such as pharmaceutical laboratories, it is crucial to secure a balance from unauthorized use or data manipulation. The new Sartorius balance can be protected by password from tampering. In addition, the Secura Cal Audit Trail function ensures that all calibration and adjustment operations performed are 100% traceable. GLP-compliant printouts and temporary blockage of data output whenever the limit conditions are not met, such as when a reading is below the minimum sample weight or the balance is not completely level, ensure traceable and reliably accurate weighing data.
Preventing Operating Errors
Weighing is an integral step in a pharmaceutical laboratory and must therefore be performed quickly, reliably and precisely. As in busy daily laboratory operations there is usually no time to study the instruction manual of a balance, this instrument must be capable of being operated intuitively.
The user interface of the Secura balance has been developed in cooperation with experienced users and therefore offers an unprecedented level of operating reliability. As a result of this cooperative development, the balance displays only the information needed at each particular time. For example, the print key appears only if a printer is connected to the balance. The color-coded info and user action fields practically rule out operating errors. The weighing applications are shown as easy-to-understand icons on the touch screen of the balance. Therefore, users can easily launch any application at the touch of a finger, without first having to study the instruction manual.