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An electrometer measures charge or potential difference in electricity and can determine electromagnetic interaction of subatomic particles. The first device was developed in the 1700s and newer models include a vibrating reed, vacuum tube, and solid-state amplifier. Modern electrometers can connect to external devices for data recording and display.
An electrometer is a device used to measure the charge or potential difference of electricity. Available in a variety of designs, the meter is essential for finding the voltage between two points in an electrical circuit. It can also be used to determine the level of electromagnetic interaction of subatomic particles.
The first electrometer was developed in the 1700s by Alessandro Volta and Abraham Bennet. This was a device that featured an electrode connected to two pieces of gold foil. The electrode was charged by direct contact or by induction. The pieces of gold foil repel each other, indicating the presence of an electric charge. The measurements were very approximate and the device had to be surrounded by lead shielding to avoid charge leakage.
Over time, many new models have been developed. The most common use of electrometers today is the recording of ionizing radiation in the field of nuclear physics. A familiar device that uses basic electrometer technology is known as a Geiger counter.
One design of a modern electrometer is an instrument that uses a vibrating reed. The basic design features a moving electrode that vibrates in relation to a fixed electrode. The combination of the two pieces creates a capacitor. When the gap between the two electrodes is altered, electric charge is forced in and out of the capacitor. The vibrating reed electrometer is very useful as the size of the instrument can be built to a very small level.
Another type of electrometer uses a vacuum tube. Inside the tube, current flows through a grid that offers high levels of input resistance. This is amplified using a polarized electrical device known as an anode circuit. This type offers very low levels of leakage current but suffers damage when salt from a human hand accumulates on the glass tube.
The newest instrument design uses a solid-state amplifier that amplifies small currents for measurement. Most modern electrometers have connections that can hook up to external devices that will record the data and create a display for viewing. The advantage of the solid state design is that it is more accurate than other versions. Compare the internal voltage with the input level. Solid-state electrometers can also measure smaller levels of electric charge than other forms of the device.
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