Electrometer - what is it? There are many different types, ranging from rare handmade mechanical tools to high-precision devices. Modern electrometers and other measuring devices are assembled using vacuum tube or solid state technology. They can be used for voltage and charge measurements with very low leakage currents, down to 1 femtoamp. The electroscope is a simpler device. It works on similar principles, but only shows the relative stress values. What does an electrometer and other instruments measure?
History of this device
The very first potential meter can be called "Early square" or simply "Square". Although the term ultimately referred to the Kelvin version, it was first used to describe a simpler device. What does an electrometer measure and what does it consist of?
It is made from an upright tree trunk to which an ivory semi-circle is attached. A light cork ball hangs from the center on a hinge. When the instrumentplaced on a charged body, the stem participates and repels the cork ball. The amount of repulsion can be read from a graduated semicircle, although the measured angle is not directly proportional to the charge. Early inventors included William Henley and Horace-Benedict de Saussure.
And who was the "pioneer" of electroscopes?
And the electroscope and electrometer - what is it and which one was better? The very first gold-leaf electroscope was by far the very first. Such a device can be found in the real world at some scientific conferences, but in general it has been replaced by a more technologically advanced version everywhere. Unlike the electrometer, it more often played the role of a sensor than a measuring instrument.
The instrument itself consists of two thin sheets of gold foil suspended from an electrode. When it is charged by induction or contact, the leaves acquire the same electrical charges and repel each other due to the Coulomb force. Their separation is a direct indicator of the accumulated net energy. On the glass opposite the leaves, pieces of tin foil can be glued so that when the leaves are completely apart, they can fall into the ground. Petals can be enclosed in a glass "envelope" to protect them from drafts. To minimize charge leakage, this envelope is insulated. Another cause of leakage is ionizing radiation, so the electrometer must be surrounded by a lead shield to prevent it.
The instrument was developed in the 18th century by severalresearchers including Abraham Bennett and Alessandro Volta.
Models from Peltier and Bonenberger
The Bonenberg measuring device consists of a single gold sheet suspended vertically between an anode and a dry pile cathode. Any charge imparted to the gold leaf causes it to move towards one pole or the other. What does the Bonenberg electrometer measure? The sign of the charged particle, as well as its approximate value.
Peltier electrometer uses a form of magnetic compass to measure deflection by balancing static force with a magnetic needle.
Modern devices
The modern electrometer is a highly sensitive voltmeter whose input impedance is so large that the current flowing into it can be considered zero for most everyday applications.
What does an electrometer measure, and what is its resistance? The actual value of the input resistance for modern devices is about 1014 ohms, compared to 1010 ohms for nanovoltmeters. Due to the extremely high input impedance, special design considerations must be applied to avoid current leakage.
Among other uses, electrometers are used in nuclear physics experiments because they are able to measure the tiny charges left in matter when ionizing radiation passes through. The most common application of modern devices is the measurement of radiation using ionization chambers in instruments such as counters. Geiger.
Valve electrometer
Valve versions use a specialized vacuum tube with very high gain and input impedance. The input current can flow into the impedance grid, and the voltage thus generated is greatly amplified in the anode (plate) circuit. Valves designed for use with electrometers have leakage currents of only a few femtoamps (10-15 amps). These valves should be handled with gloved hands, as s alts remaining on the glass envelope can create leakage paths for these tiny currents.
In a specialized circuit called "inverted triode", the roles of anode and grid are reversed. This places the control element as far away as possible from the space charge region surrounding the filament, minimizing the number of electrons collected by the control circuit and thus minimizing the input current.
The most advanced electrometers
Most modern measuring instruments consist of a solid state amplifier using one or more FETs, connections for connecting external measuring devices, and usually a connection. For a solid state electrometer, the photo is shown above.
The amplifier amplifies a small current to make it easier to measure it. External connections are usually of coaxial or triaxial design and allow the installation of diodes or ionization chambers to measure ionizing radiation. Connections to a display or data logging equipment allow the user to view data or record data for later analysis.
Electrometers designed for use with ionization chambers may include a high voltage power supply that is also used to bias the ionization chamber.
