These electronic scales are a device for the precise determination of the mass of substances and objects in educational institutions. They are used in biology, physics and astronomy, chemistry lessons and in laboratory practicals for dosing reagents and measuring the mass of solutions and solid materials, with a measurement accuracy of 0.1 g. The scales determine mass together with a vessel through taring and also count the number of identical objects from their total mass. The device is operated by the teacher or a specialist familiar with the rules of use, students work with the scales only under the supervision of an adult, and the recommended age of learners is from 10 years, that is pupils of grade 5 and above.
The scales are a compact digital device with a liquid crystal five-digit display, simple controls and automatic switch-off after 60 seconds of inactivity. The maximum weighing limit is 500 g, the measurement discreteness is 0.1 g and the measurement accuracy is 0.1 g. The units of measurement are grams, ounces, pounds and kilograms, and the taring range covers the whole weighing limit. The weighing platform is set on a stable base, the body is made of plastic and the platform of plastic or metal, and both allow wiping with a dry or slightly damp cloth. Power comes from batteries, whose type is given on the body, so no external power source is needed, and the working temperature is from 5 to 35 °C. The scales are installed on a table, on a level horizontal surface, and need no adjustment before the first use. Marking and operating documentation are in Ukrainian, the marking carries the trade mark, the model and a place for the inventory number, and the documentation comprises the passport with the warranty coupon and the operating instructions. The service life is 5 years and the warranty period is 12 months.
The set includes the assembled electronic scales — 1 pc; power batteries, of the type and number given on the body, supplied either with the set or separately depending on the region of sale; the passport with the warranty coupon — 1 pc; and packaging for storage and transport — 1 pc, an individual corrugated cardboard box with the contents fixed inside. Consumable parts such as batteries are not covered by the warranty.
The scales are placed on a clean, level, horizontal surface away from draughts and vibration, the batteries are inserted according to the polarity marks and the compartment cover is closed tightly. The ON/OFF key switches the device on and the display shows 0.0, after which the scales are left on for 1 to 2 minutes so that the readings stabilise; if the device was transported or stored below 5 °C it is kept at room temperature for one hour first. For ordinary weighing an empty vessel is put on the clean dry platform, the readings are allowed to settle and the TARE key is pressed so that the display shows 0.0, and the substance is then put into the vessel and the display shows the net mass. The MODE key, pressed once or several times, selects the unit of measurement and the selected unit is kept until the next switch-off, and the LIGHT key turns the display backlight on and off for work in poor lighting. In the object counting mode a known number of identical small objects, 25, 50, 75 or 100 pieces, is placed on the platform, the PCS key is held for 2 seconds until the display shows 100, the MODE key selects the number in the reference portion and the PCS key confirms the choice, after which the device shows the number of the objects placed on the platform.
Substances are placed on the platform only in a suitable vessel such as a bowl or a glass container; liquids and solutions are never placed directly on the platform, aggressive and corrosive substances are kept from spilling onto the body, and after each measurement the vessel is removed and the platform is wiped dry. The maximum weighing limit given on the body is not exceeded, objects are not dropped onto the platform and heavy loads are not lowered abruptly, since this damages the sensor, and the scales are not used as a support for other objects. The device runs on low-voltage batteries, which is safe for the user, but it is not washed under running water or immersed in liquid, moisture must not get inside through the ventilation openings, and if water does get in, work is stopped and the service centre is contacted. The scales are not used outside the working temperature range, above 35 °C or below 5 °C, and are not kept in high humidity or near heat sources and direct sunlight. The body and the platform are wiped with a soft dry or slightly damp cloth, dust is removed with a soft brush, and abrasive materials, organic solvents, acetone and aggressive detergents are not used. Once a month the device is checked to show zero when switched on with an empty platform; if the readings do not return to zero the TARE key is pressed, and if the display dims or the readings become unstable the batteries are replaced. The scales need no regular calibration by the user, and the accuracy limits are checked only at a service centre. For storage longer than a month the batteries are taken out so that leaking electrolyte cannot damage the device.
