ClipArt ETC
"In all the arc lamps in common use, the coil, by means of which the automatic maintenance of the arc is kept up, is placed as a shunt across the its poles."—Finley, 1917

Arc lamp

"In all the arc lamps in common use, the coil, by means of which the automatic maintenance of the arc…

"The coil is of flat, rectangular shape, with a narrow central opening just large enough to allow one of the magnets of the astatic system to swing freely. The other magnet swings over a graduated circle placed on the top of the coil, and serves also as an index. Sometimes a mirror and scale are substituted for the index and graduated circle. The sole on which the coil stands is movable on a fixed piece which can be levelled by means of three screws." &mdash Encyclopedia Britannica, 1893

Astatic Multiplier

"The coil is of flat, rectangular shape, with a narrow central opening just large enough to allow one…

A device used to measure an unknown resistance of a resistor by balancing two legs of a bridge circuit.

Wheatstone Bridge

A device used to measure an unknown resistance of a resistor by balancing two legs of a bridge circuit.

"In the Deprez-d'Arsonval dead-beat galvanometer, a moveable coil is suspended between the poles of a string, permanent U-magnet that is fixed. The coil consists of many turns of fine wire the terminals of which above and below serve as the supporting axis. Within the coil is an iron tube that is supported form the back, and that serves to concentrate the magnetic field. The passage of current turns the coil, and sets it so that its plane encloses a larger number of liens of force. this movement of the coil turns the mirror by means of which the angles of deflection are read with a telescope and scale." -Avery 1895

Deprez-d'Arsonval Dead-Beat Reflecting Galvanometer

"In the Deprez-d'Arsonval dead-beat galvanometer, a moveable coil is suspended between the poles of…

"An electrodynamometer is a galvanometer with two coils, at least one of which is movable, and through at least one of which the curent to be measured passes. It is very useful in the measurement of alternating curernts and voltages." -Avery 1895

Electrodynamometer

"An electrodynamometer is a galvanometer with two coils, at least one of which is movable, and through…

A funnel-shaped piece of brass is placed over the ends of a galvanometer when the resistance is equal to that of the pile. This acts as a preservative for the junctions from the heat radiated by the surrounding objects.

Funnel-shaped Brass

A funnel-shaped piece of brass is placed over the ends of a galvanometer when the resistance is equal…

A galvanometer is a type of ammeter; an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection, through a limited arc, in response to electric current flowing through its coil. The term has been expanded to include uses of the same mechanism in recording, positioning, and servomechanism equipment.

Galvanometer

A galvanometer is a type of ammeter; an instrument for detecting and measuring electric current. It…

"The galvanometer is an instrument for determining the strength of an electric current by means of the deflection of a magnetic needle around which the current flows. When a galvanoscope is provided with a scale so that the deflections of its needle may be measured, it becomes a galvanometer." — Avery, 1895

Astatic galvanometer

"The galvanometer is an instrument for determining the strength of an electric current by means of the…

"The galvanometer is an instrument for determining the strength of an electric current by means of the deflection of a magnetic needle around which the current flows. When a galvanoscope is provided with a scale so that the deflections of its needle may be measured, it becomes a galvanometer." — Avery, 1895

Tangent galvanometer

"The galvanometer is an instrument for determining the strength of an electric current by means of the…

An old lamp attached to a galvanometer.

Old Lamp

An old lamp attached to a galvanometer.

A potentiometer instrument for measuring the potential (or voltage) in a circuit taps off a fraction of a known voltage from a resistive slide wire and compares it with the unknown voltage by means of a galvanometer. The sliding tap of the potentiometer is adjusted and the galvanometer briefly connected to both the sliding tap and the unknown potential; the deflection of the galvanometer is observed and the sliding tap adjusted until the galvanometer no longer deflects. At that point the galvanometer draws no current from the unknown source, and the magnitude of voltage can be calculated from the position of the sliding contact. This null balance method is a fundamental technique of electrical metrology.

Potentiometer

A potentiometer instrument for measuring the potential (or voltage) in a circuit taps off a fraction…

An illustration of Macedonio Melloni's thermomultiplier, a combination of thermopile and galvanometer.

Thermomultiplier

An illustration of Macedonio Melloni's thermomultiplier, a combination of thermopile and galvanometer.

"A very convenient form of Thomson's galvanometer, the only specimen of its kind we have seen. The peculiarity of its construction consists in the connection between the scale and the galvanometer, which saves much trouble in adjusting the instrument." — Encyclopedia Britannica, 1893

Thomsons Galvonometer

"A very convenient form of Thomson's galvanometer, the only specimen of its kind we have seen. The peculiarity…

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895

Wheatstone Bridge

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895

Wheatstone Bridge in Circuit

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895

Wheatstone Bridge with Resistors

"The Wheatstone bridge is used as a way to measure resistance of a unknown resitors." -Avery 1895