Galvanometers

The first instrument used to measure the strength, direction, and presence of an electric current in a conductor was a galvanometer. Their design is based on the premise that a magnetic needle moves in the presence of electric current in a conductor placed near the galvanometer. When the current flows through the conductor, the needle turns parallel to the line of induction about the conductor. The north pole points in the induction flow’s direction and how much the needle turns is based on the electrical current’s overall strength.

Who Invented the Galvanometer?

André-Marie Ampère is credited with inventing the galvanometer in 1824. The first type was a tangent galvanometer, which had a compass surrounded by a coil of wire. The tangent of the angle the needle was moved on was proportional to the current’s strength in the coil being measured. These original galvanometers were later improved upon by putting the compass in the center of a more precisely measured circle, which significantly improved their accuracy. Even later, the compass was replaced with a meter and leveling screws were then added to the devices.

What Are Reflecting Galvanometers?

The early tangential galvanometers were limited in that their needles had to be very short to minimize the effects of the earth’s magnetic field and other errors on the device’s measurements. The short needle made it hard to measure small changes in electrical current. The reflecting galvanometer solved this problem as it replaced the needle with a beam of light that was reflected off of a mirror onto a scale placed three feet from the device. These permitted small current changes to be measured.

String Galvanometers

Suspending the device’s needle at the end of a string further improved the sensitivity of galvanometer measurement. Astatic models used two needles mounted in parallel with opposite poles to neutralize the effect of the earth’s magnetic field.

Galvanometer Improvements

In the late 1800s, attaching a small coil to the meter needle and then placing them in a permanent magnetic field improved galvanometer performance. This improvement in performance made the tangential galvanometers obsolete.

What Are Galvanometers Used for Today?

In the early 20^th century, galvanometers were widely used to search for faults in phone cables. They were used in analog meters in electrical equipment throughout the 1980s, but digital meters and readouts later replaced them. Today, they are used in positioning and control systems in industry, head positioning servers on some computer hard disk drives, beam steering applications and research, and in laser marking and projection.