Questions tagged [dielectric]

A dielectric is an insulator that can be polarized by applying an electric field. A common example is the use of a dielectric within a capacitor between the metallic plates to increase the surface charge.

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3 answers
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Voltage required for a spark plug - dielectric constant of air

The dielectric constant of air is approximately 3 kV/mm. The typical space between car spark plugs is between 0.6 and 1.8 mm. By multiplying those numbers in mm by the dielectric constant of air, we ...
1 vote
1 answer
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Dielectric strength test voltage

I am preparing an insulation diagram prior to testing a device against IEC 60601-1. How do I determine the dielectric strength test voltage? I couldn't find anything in -1.
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1 answer
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Why do material makers call the dielectric constant "Dk" rather than "D.c."?

Why do material makers call the dielectric constant "Dk" rather than "D.c."? Is it kind of German? Something like Dielektrische Konstante? It is actually called a ...
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DC hipot leakage current

I noticed that when testing hipot in DC I always get leakage current, but not during AC hipot testing. Do you have any ideas about this? My hipot tester is Quadtech Sentry 500VA. I’m testing a ...
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2 answers
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Would an inductor work differently under a different dielectric environment?

I am talking about these common rounded inductors with a metal core that you would find on PCBs. Would the operation be different in, say, mineral oil vs. air? These are two different dielectric ...
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Is the ground plane in patch antenna used as a reflector? If so, how does the distance between ground plane and patch affect the reflected signals?

For a reflector to work it should be placed quarter wavelength away from the source so that waves reflected back from the ground plane are in phase with the waves being generated and superimpose. In ...
3 votes
1 answer
287 views

How does selecting a higher permittivity substrate in patch antenna reduce its size?

By selecting a higher permittivity substrate do we reduce the height of the antenna or we reduce the length of the patch antenna? We cannot reduce the length of the antenna as it is dependent on the ...
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1 answer
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Relays: What is High Contact Stability?

This TE RF relay datasheet shows the component coming in three varieties: High Dielectric High Contact Stability High Current So high-current is obvious (right?), and (correct me if I'm wrong) high ...
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Why do dielectric waveguides support hybrid modes and metallic waveguides do not?

Can anyone explain to me qualitatively why dielectric waveguides (core and infinite cladding) support hybrid modes (E_z and H_z components in the guided wave), while metallic waveguides cannot? I am ...
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The field in a waveguide at exactly the cut-off frequency

Can anyone explain to me qualitatively, what kind of field exists inside a waveguide at EXACTLY the cut-off frequency? I would be grateful if an explanation was given about waveguides with metalic ...
1 vote
2 answers
66 views

How to increase efficiency of antenna without moving antenna far from tree?

I have designed a monopole antenna at 868MHz frequency. Now I would like to attach that antenna to the tree (wood). But, due to Why does placing an antenna far from the wood increase the efficiency of ...
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1 answer
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Why does placing an antenna far from the wood increase the efficiency of the antenna?

I designed a monopole antenna at 868MHz frequency. I placed wood as the surrounding material. I noticed that placing the antenna far from the wood increases the efficiency of the antenna. Can anyone ...
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1 answer
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Dielectric withstand test of DC powered product

I am trying to figure if our test set-up for dielectric withstand test is correct. There are two versions of the DUT (device under test), an AC powered (typical 85-264 Vrms) and DC powered type (12-...
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Ampere's Law with dielectric

I am asked to calculate the magnetic-field-strength and magnetic-flux-density for different regions inside a coaxial-cable. I found Ampere's Law for that, but it uses \$\mu_0\$ , and the coaxial-cable ...
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3 answers
775 views

Following is an excerpt from a power electronics textbook. Is the statement true?

As far as I know ESR primarily depends on the type of dielectric. eg: Al electrolytic (higher capacitance value) would have much higher ESR than ceramic (usually lower capacitance value). Say for ...
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Capacitors: voltage-dependent capacitance?

While playing around with a capacitive power supplies, I observed some very weird behavior when passing a 60Hz sinusoidal current through a 1000V disk ceramic capacitor. The voltage curve was very ...
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1 answer
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The equation of surface charge density is incorrect with only the sign is opposite of capacitor of cylinder form

The capacitor of the 2 cylinders exists. As shown in the diagram, the righter space has been filled with the dielectric of \$ \epsilon_{1} \$ and the lefter space has been filled with the dielectric ...
2 votes
2 answers
233 views

How do I calculate the capacitance of a capacitive touch or water sensor?

Sensors like capacitive touch or moisture sensors are simply two traces drawn on a PCB. For example, you may check the Grove soil moisture sensor. In these types of sensors, the capacitance increases ...
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Why it can be asserted that the bottom plate takes the highest potential and the top plates takes the lowest of the capacitor?

The ideal parallel capacitor has been filled with 2 dielectrics as shown in the above diagram. $$ V_{1} :=\text{potential at the top plate} $$ $$ V_{2} :=\text{potential at the bottom plate} $$ $$...
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When is PCB thermal destruction desirable?

In the Wikipedia page for FR-4, it contains this excerpt: FR-4 epoxy resin systems typically employ bromine, a halogen, to facilitate flame-resistant properties in FR-4 glass epoxy laminates. Some ...
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1 answer
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Why the euclid distance between the plates of the capacitor has been doubled to find out the capacitance?

I may have been asking of an easy problem. The problem requires to find out the capacitance. The ideal capacitor with area of \$S\$ exists and the euclid distance between the plates is \$d\$. The ...
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Does supercapacitor electrode need dielectric layer?

I am trying to build a super capacitor. I use Activated Carbon with Wood Glue, aluminium tin can as electrode, multi layers of tissue paper as separator, and table salt water as electrolyte. No matter ...
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Characteristic Impedance of Multi-Dielectric Coplanar Waveguide

Background I've calculated the characteristic impedance of a CoPlanar Wave Guide (CPWG) type transmission line on my 8-layer stack-up between L1 - top layer and L2 - GND1 directly underneath it. The ...
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Refractive index, wavenumber, and wave impedance of the PEC that a plane wave is normally incident on

I am trying to find the refractive index \$n_t\$, wavenumber \$k_t\$, and wave impedance \$\eta_t\$ of a perfect electric conducting medium t. Here is my work so far: The conductivity of the PEC is \$...
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Impedance of an embedded microstrip with different sub- and superstrate

I have been trying to find a formula to calculate the impedance of an embedded microstrip where the substrate has a different dielectric constant to the superstrate (so the stack up is conducting ...
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2 votes
2 answers
489 views

How to design an amplifier for a sensing liquid level using capacitive probes?

In this problem I have a capacitor that is submerged in a varying level of dielectric fluid. Therefore, the capacitance varies linearly with the height of the fluid. How should I design a simple op ...
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How fast is DC current/voltage?

The standard way to calculate the speed of information (current/voltage, EM wave) through a dielectric medium (like PTFE or fiber) is to determine the relative dielectric constant, and compute the ...
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Calculating the permitivity of PCBs

I've read that the permitivity of FR-4 is around 4.5, however I would like to measure the permitivity of an actual double sided copper clad board, the way I am thinking is to measure the thickness of ...
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Can you use 'Rubber,' Specifically Liquid Electrical Tape Between The Plates of a DIY Capacitor

The above is pretty much all there is to the question. By "can you," I mean will it be properly effective / are there any tips? If not, why? It seems that this ought to work, but I can't ...
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Can I calculate minimum rise time of a transmission line if I know the length and the loss tangent?

Overview: I am trying to work out if it's possible to transmit my 1.2Gbps MIPI data down a 600mm long flexible PCB strip. Assuming I have the impedance correct, will the signal still be degraded by ...
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BIL, Dielectric Breakdown, Shrink Wrap, and Safety. Is there a resource for this information?

I am currently working with a system that produces high voltage transients for system testing, and have some cables that need to be made/modified to work with some new equipment. The operating ...
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1 answer
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What material should I use for the plates of my homemade mica capacitors?

I recently acquired some mica as i want to build my own high voltage (50 kV if possible) capacitors. The problem I am encountering right now is that the surface of such a crystal isn't perfectly flat ...
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2 answers
892 views

What material can I use as a dielectric in my own high voltage capacitors?

I need capacitors rated for 50 kV. Buying them is an option but the ones with appropriate voltage rating I have seen cost more than 50€ which is far too much. That's why I want to make caps on my own ...
0 votes
1 answer
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Relation ship between Track width, Impedance, Dielectric and copper thickness

I like to know the relationship between different factors like track width, impedance, dielectric and copper thickness. After quite a reading I got to know that as the track width of a cline is ...
3 votes
2 answers
273 views

How come distilled water hasn't replaced transformer oil as a high voltage insulator?

I've noticed that distilled water has an extremely high dielectric straight (65-70 MV/m). With that considered, how come it isn't used in the place of transformer oil for 10-20 kV applications where ...
2 votes
1 answer
402 views

PCB Layer Stack Dielectric Constant Math

I have a question reference PCB layer stack and the adding multiple dielectric constants together. The image and description below should help clarify the question: The differential pair will be ...
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1 answer
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What are the "poles" of a signal (after it's reflected perhaps)

I desire to learn about "estimating the poles of a resonant signal", specifically the complex natural resonance of objects. However, I don't know what "poles" are. What would you suggest I look up ...
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1 answer
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HF characteristics of Liquid Electrical Tape

Some self-wound toroid inductors from a HF-radio kit are sitting a bit too loose on their PCB for my liking; they stand upright and are only held in place by the thin enamel-coated inductor wire that ...
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1 answer
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How can the dielectric constant of water be so high but water on electric devices can cause a short circuit? [closed]

Is it only the fact that pure water has a high dielectric constant and non-pure water i.e. the water that usually causes a short circuit is contaminated and it's the contamination mixture in the water ...
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1 answer
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C0G vs polypropylene capacitors in signal filtering

Can anybody give me a comprehensive pros and cons list or explanation about the differences between C0G (NP0) ceramic and polypropylene capacitors? I would like to use them in signal filtering and ...
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208 views

Grounding polycarbonate or Plexiglas

If a record turntable's base is made from a 2" think piece of acrylic (for instance polycarbonate or Plexiglas) can it be successfully grounded to eliminate any static charge that it would build up in ...
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termination of a parallel wire differential transmission line as delay line on variable dielectric constant medium

Well this has quite a long title, lets explain the situation I'm currently working on the design of a sensor to measure the dielectric permittivity of a liquid medium, the idea is to use a ring ...
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1 answer
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PEC-backed dielectric material

For the paper named "Antenna Miniaturization and Bandwidth Enhancement Using a Reactive Impedance Substrate" the statement "PEC-backed dielectric material", so what is the meaning of this statement? ...
3 votes
3 answers
185 views

High voltage dielectric breakdown & layering insulators

I’m going to use 230 kV as the reference voltage for the example below; I know if I put a piece of metal too close to a 230 kV source it will breakdown the air and jump to the piece of metal causing a ...
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Capacitance of circular parallel plate capacitors

I've been trying to solve this question for a while now , but I can't seem to get to the written solution. Question : Calculate the capacitance of a parallel capacitor having two identical conductor ...
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1 answer
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Dielectric Loss for Constant Impedance

Are dielectric losses the same for two different 50ohm structures that are built in the same dielectric medium? Eg. Two 50ohm Stripline traces in FR4 where one is very skinny with close GND planes, ...
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What would be the combined dielectric constant of two dielectrics in series?

Let's say we have two parallel conductor plates. In the middle, there is not one but two layers of dielectrics made of different materials. If we know the relative permittivity of each dielectric, how ...
7 votes
3 answers
9k views

What lubricant is suitable for switch contact?

I have this expensive DPDT switch (20A 250V 2hp) which the only problem is dirty encumbered inside. The encumbrance is made of carbonized material and some kind of wax and dirty electrical contacts. ...
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1 answer
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variation of thickness of dielectric layer for different textile-based capacitive pressure sensors

For my thesis I am working with textile-based capacitive pressure sensors and I am struggling to see how much variation in thickness of the dielectric layer you can have before you have noticeable ...
2 votes
1 answer
289 views

How far does reforming a capacitor help? Does it have any adverse effect on using such a capacitor on components?

I read a few articles on the internet about reforming capacitors. Does this actually apply only to a capacitor that was stored during a certain period of time or can it be used on any electrolytic ...