Education/demonstration model - Composite - 1970-1980 - Polish galvanometer, PRL

A rarely encountered, large universal demonstration galvanometer – an impressive educational aid intended for a school or university physics laboratory. The device most likely originates from Poland and was manufactured in the PRL period as a small‑batch or workshop product, probably by a specialized workshop producing didactic equipment. It is a carefully made, yet unusual construction, and the lack of a factory nameplate indicates it was not mass-produced. A model from the 1970s. The instrument is mounted on a sturdy wooden base and enclosed in a construction with transparent glass covers, allowing students not only to observe the deflection of the large needle but also the operation of the internal mechanism, coils, magnet, springs, electrical connections, and the regulating circuit. It is in essence a magnified and exposed interior of a classic analog meter, designed so that the principle of its operation could be observed by the whole class at once. When current is supplied to the movable coil placed in a magnetic field, a torque is produced that turns the coil together with the long needle. Delicate springs oppose the movement, so the needle settles at a position where the electromagnetic force is balanced by the spring force. The direction of deflection allows identifying the polarity of the current, while the magnitude of deflection corresponds to its intensity. The device was perfectly suited for impressive demonstrations of electromagnetic induction – for example, when a magnet was inserted into and withdrawn from the coil, the needle deflected alternately in opposite directions, showing the change in the direction of the induced current. The galvanometer could also serve as a balance indicator in Wheatstone bridge experiments. A removable dial with a scale and a module containing a shunt or multiplier was placed in the upper part of the instrument, enabling the same mechanism to be used as a galvanometer, ammeter, or voltmeter with different ranges; with an appropriate rectifying arrangement it was also possible to conduct demonstrations with alternating current. The offered specimen does not include a removable dial with a scale, cables, or instructions – it is sold solely as shown in the photographs. Dimensions: 29 × 29 × 12.5 cm. Condition consistent with the photos, with natural signs of age and previous use: visible wear and scratches on the wood, dirt, localized dulling of the transparent covers, and oxidation traces on metal components. The device has not been tested, as I do not have suitable equipment or spare measuring modules. I do not know whether it works correctly, so it is offered as an untested item of unknown technical condition, primarily for collection, a museum of technology, a historical physics classroom, display, or potential professional restoration.

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