Drehspulinstrument und Weicheiseninstrument

Drehspulinstrument

• These instruments utilize a coil (rotor) that rotates within a magnetic field.
• The rotation is proportional to the current flowing through the coil.
• A pointer attached to the coil indicates the current reading on a calibrated scale.
• They are generally more accurate and sensitive than other moving-coil instruments.
• They can measure both direct and alternating current (AC) with appropriate modifications.
• Common use cases include measuring small currents and voltages in various electrical circuits.
• They often require a sensitive suspension mechanism to minimize friction and allow for accurate rotation.
• Their operation relies on the interaction between the current-carrying coil and the magnetic field; this creates a torque that causes the coil to rotate.

Weicheiseninstrument

• These instruments rely on the magnetic properties of iron or other ferromagnetic materials.
• In operation, a current-carrying coil creates a magnetic field that attracts or repels a soft iron core.
• The movement of the iron core causes a pointer to deflect on a calibrated scale.
• These types of instruments are typically robust and reliable but less sensitive than moving-coil instruments.
• They are appropriate for measuring larger currents.
• They are relatively simple in construction.
• The magnetic field strength is directly proportional to the current.
• The deflection of the pointer is directly proportional to the square of the current.
• Applications often include measuring currents and voltages in household appliances and industrial equipment.

Hitze-Draht Temperaturmeter

• These instruments use the principle that the resistance of a heated wire changes proportionally to temperature.
• A fine wire, usually of platinum or tungsten, is heated by the current passing through it.
• The changing resistance is measured and related to the temperature via a calibrated scale.
• Accuracy depends on the material used and the calibration.
• Commonly used to measure temperatures in specific ranges.
• The wire's heating is directly proportional to the square of the current.
• The material of the wire is selected for its predictable resistance-temperature relationship.
• These types of instruments often find use in industrial settings for measuring and monitoring processes.
• A change in temperature results in a change in resistance, which in turn affects the current flow, causing a deflection of the galvanometer pointer.