Basic definition of dielectric constant tester

According to the research results of electrostatics, an isolated charge q in a vacuum generates an electric field E around it, and an electric field force is applied when another test charge q0 enters the electric field. The electric field strength produced by the charge q is:

Where ε0 is the dielectric constant in vacuum; r is the radial distance from the point charge q. In general, the electric field strength is a vector. The electric field force experienced by the test charge q0 at a distance r from the charge q is:

According to the reaction property of the force, the charge q is also affected by the force of the electric field generated by the test charge q0 and the magnitude of the force is equal and opposite. According to equation (1), the dielectric constant ε0 in vacuum characterizes the magnitude of the electric field strength generated by the isolated charge q over a given distance r. If the vacuum condition in equation (1) is replaced by a dielectric, the electric field strength produced by the same isolated charge q will be expressed as

Where ε is the dielectric constant of the dielectric. In practical applications, the dielectric constant ε0 in vacuum is usually selected as a reference, and the ratio of the dielectric constant ε of the dielectric to ε0 is defined as a dimensionless relative permittivity εr, as in equation (4). Show:

Since vacuum is an ideal dielectric model (no atoms, molecules), the electric field generated by the original charge q is reduced in the actual dielectric due to the bound charge effect, which is unlikely to occur in vacuum. Therefore, the relative dielectric constant Er for the actual dielectric always satisfies greater than or equal to 1.

It can be seen from equation (3) that the dielectric constant ε represents a constraint on the magnitude of the electric field strength generated by the charge q in the dielectric (in addition to the distance, it is also the only constraint). Obviously, this inference is completely acceptable in the case of an electrostatic field, but it seems to be somewhat inadequate to apply this inference directly to the alternating electric field. The research on the microscopic representation mechanism and macroscopic effect of dielectric under alternating electric field has achieved some results, but it still needs further research. It is also one of the important research directions and contents of dielectric physics and quantum physics.

It can be confirmed that the property characterized by the dielectric constant of the dielectric also affects the alternating electric field in the case of an alternating electric field. For example, the propagation velocity of an alternating electric field in a dielectric will decrease, the frequency will be constant, the wavelength will be shorter (electromagnetic propagation theory) and the dielectric constant will be larger, and the corresponding change will be greater.

Basic definition of dielectric constant tester

Main technical indicators of dielectric constant tester:

2.1 tanδ and ε performance:

2.1.1 Test of tan δ and ε changes of solid insulation materials with test frequencies from 10 kHz to 120 MHz.

2.1.2 tanδ and ε measurement range:

Tan δ: 0.1 to 0.00005, ε: 1 to 50

2.1.3 tanδ and ε measurement accuracy (1MHz):

Tanδ: ±5%±0.00005, ε: ±2%

Operating frequency range: 50kHz ~ 50MHz four-digit display, voltage controlled oscillator

Q value measurement range: 1 to 1000 three-digit display, ±1Q resolution

Adjustable capacitance range: 40 ~ 500pF ΔC ± 3pF

Capacitance measurement error: ±1% ± 1pF

Q table residual inductance value: about 20nH

Dielectric constant tester features:

◎ The company's innovative automatic Q-value retention technology enables the Q resolution to be measured to 0.1Q, resulting in a tan δ resolution of 0.00005.

◎ A test for the dielectric loss angle (tan δ) and dielectric constant (ε) of a solid insulating material at 10 kHz to 120 MHz.

◎ The residual inductance of the tuning loop is as low as 8nH, which guarantees less error in (tanδ) and (ε) of 100MHz.

◎Special LCD screen menu display multi-parameters: Q value, test frequency, tuning status, etc.

◎ Q value range automatic / manual range control.

◎ DPLL synthesis 1kHz ~ 60MHz, 50kHz ~ 160MHz test signal. Independent signal source output, so this unit is a composite signal source.

◎The test device meets the requirements of national standard GB/T 1409-2006, American standard ASTM D150 and IEC60250.

The dielectric constant tester operates from 10 kHz to 120 MHz and is capable of testing the high frequency dielectric loss (tan δ) and dielectric constant (ε) of materials in the operating frequency.

The test device in this instrument is composed of a plate capacitor and a micro-cylinder linear capacitor. The plate capacitor is generally used to clamp the sample to be tested, and the Q meter is used as the indicating instrument.

The loss tangent of the insulating material is calculated by the formula by placing the measured sample into the plate capacitor and not changing the Q value of the sample and the scale reading of the thickness.

Similarly, the capacitance reading of the microcapacitor linear capacitor is changed, and the dielectric constant is calculated by the formula.