Update Content - 2022-03-15
This commit is contained in:
@@ -1,16 +1,16 @@
|
||||
+++
|
||||
title = "Grounding and Shielding: Circuits and Interference"
|
||||
author = ["Thomas Dehaeze"]
|
||||
author = ["Dehaeze Thomas"]
|
||||
description = "Explains in a clear manner what is grounding and shielding and what are the fundamental physics behind these terms."
|
||||
keywords = ["Electronics"]
|
||||
draft = false
|
||||
+++
|
||||
|
||||
Tags
|
||||
: [Electronics]({{< relref "electronics" >}})
|
||||
: [Electronics]({{< relref "electronics.md" >}})
|
||||
|
||||
Reference
|
||||
: ([Morrison 2016](#org7a49345))
|
||||
: (<a href="#citeproc_bib_item_1">Morrison 2016</a>)
|
||||
|
||||
Author(s)
|
||||
: Morrison, R.
|
||||
@@ -22,7 +22,6 @@ Year
|
||||
## Voltage and Capacitors {#voltage-and-capacitors}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This first chapter described the electric field that is basic to all electrical activity.
|
||||
The electric or \\(E\\) field represents forces between charges.
|
||||
@@ -53,9 +52,9 @@ This displacement current flows when charges are added or removed from the plate
|
||||
|
||||
### Field representation {#field-representation}
|
||||
|
||||
<a id="orga3615d0"></a>
|
||||
<a id="figure--fig:morrison16-E-field-charge"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_E_field_charge.svg" caption="Figure 1: The force field lines around a positively chaged conducting sphere" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_E_field_charge.svg" caption="<span class=\"figure-number\">Figure 1: </span>The force field lines around a positively chaged conducting sphere" >}}
|
||||
|
||||
|
||||
### The definition of voltage {#the-definition-of-voltage}
|
||||
@@ -64,22 +63,22 @@ This displacement current flows when charges are added or removed from the plate
|
||||
### Equipotential surfaces {#equipotential-surfaces}
|
||||
|
||||
|
||||
### The force field or \\(E\\) field between two conducting plates {#the-force-field-or--e--field-between-two-conducting-plates}
|
||||
### The force field or \\(E\\) field between two conducting plates {#the-force-field-or-e-field-between-two-conducting-plates}
|
||||
|
||||
<a id="org82b88ec"></a>
|
||||
<a id="figure--fig:morrison16-force-field-plates"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_force_field_plates.svg" caption="Figure 2: The force field between two conducting plates with equal and opposite charges and spacing distance \\(h\\)" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_force_field_plates.svg" caption="<span class=\"figure-number\">Figure 2: </span>The force field between two conducting plates with equal and opposite charges and spacing distance \\(h\\)" >}}
|
||||
|
||||
|
||||
### Electric field patterns {#electric-field-patterns}
|
||||
|
||||
<a id="org16f20a9"></a>
|
||||
<a id="figure--fig:morrison16-electric-field-ground-plane"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_electric_field_ground_plane.svg" caption="Figure 3: The electric field pattern of one circuit trace and two circuit traces over a ground plane" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_electric_field_ground_plane.svg" caption="<span class=\"figure-number\">Figure 3: </span>The electric field pattern of one circuit trace and two circuit traces over a ground plane" >}}
|
||||
|
||||
<a id="org38210cb"></a>
|
||||
<a id="figure--fig:morrison16-electric-field-shielded-conductor"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_electric_field_shielded_conductor.svg" caption="Figure 4: Field configuration around a shielded conductor" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_electric_field_shielded_conductor.svg" caption="<span class=\"figure-number\">Figure 4: </span>Field configuration around a shielded conductor" >}}
|
||||
|
||||
|
||||
### The energy stored in an electric field {#the-energy-stored-in-an-electric-field}
|
||||
@@ -88,11 +87,11 @@ This displacement current flows when charges are added or removed from the plate
|
||||
### Dielectrics {#dielectrics}
|
||||
|
||||
|
||||
### The \\(D\\) field {#the--d--field}
|
||||
### The \\(D\\) field {#the-d-field}
|
||||
|
||||
<a id="org5a4329e"></a>
|
||||
<a id="figure--fig:morrison16-E-D-fields"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_E_D_fields.svg" caption="Figure 5: The electric field pattern in the presence of a dielectric" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_E_D_fields.svg" caption="<span class=\"figure-number\">Figure 5: </span>The electric field pattern in the presence of a dielectric" >}}
|
||||
|
||||
|
||||
### Capacitance {#capacitance}
|
||||
@@ -122,7 +121,6 @@ This displacement current flows when charges are added or removed from the plate
|
||||
## Magnetics {#magnetics}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This chapter discusses magnetic fields.
|
||||
As in the electric field, there are two measures of the same magnetic field.
|
||||
@@ -150,11 +148,11 @@ In a few elements, the atomic structure is such that atoms align to generate a n
|
||||
The flow of electrons is another way to generate a magnetic field.
|
||||
|
||||
The letter \\(H\\) is reserved for the magnetic field generated by a current.
|
||||
Figure [6](#org9b0e888) shows the shape of the \\(H\\) field around a long, straight conductor carrying a direct current \\(I\\).
|
||||
Figure [6](#figure--fig:morrison16-H-field) shows the shape of the \\(H\\) field around a long, straight conductor carrying a direct current \\(I\\).
|
||||
|
||||
<a id="org9b0e888"></a>
|
||||
<a id="figure--fig:morrison16-H-field"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_H_field.svg" caption="Figure 6: The \\(H\\) field around a current-carrying conductor" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_H_field.svg" caption="<span class=\"figure-number\">Figure 6: </span>The \\(H\\) field around a current-carrying conductor" >}}
|
||||
|
||||
The magnetic field is a force field.
|
||||
This force can only be exerted on another magnetic field.
|
||||
@@ -169,7 +167,7 @@ Ampere's law states that the integral of the \\(H\\) field intensity in a closed
|
||||
\boxed{\oint H dl = I}
|
||||
\end{equation}
|
||||
|
||||
The simplest path to use for this integration is the one of the concentric circles in Figure [6](#org9b0e888), where \\(H\\) is constant and \\(r\\) is the distance from the conductor.
|
||||
The simplest path to use for this integration is the one of the concentric circles in Figure [6](#figure--fig:morrison16-H-field), where \\(H\\) is constant and \\(r\\) is the distance from the conductor.
|
||||
Solving for \\(H\\), we obtain
|
||||
|
||||
\begin{equation}
|
||||
@@ -181,29 +179,29 @@ And we see that \\(H\\) has units of amperes per meter.
|
||||
|
||||
### The solenoid {#the-solenoid}
|
||||
|
||||
The magnetic field of a solenoid is shown in Figure [7](#orgd3a9cf9).
|
||||
The magnetic field of a solenoid is shown in Figure [7](#figure--fig:morrison16-solenoid).
|
||||
The field intensity inside the solenoid is nearly constant, while outside its intensity falls of rapidly.
|
||||
|
||||
Using Ampere's law \eqref{eq:ampere_law}:
|
||||
Using Ampere's law <eq:ampere_law>:
|
||||
|
||||
\begin{equation}
|
||||
\oint H dl \approx n I l
|
||||
\end{equation}
|
||||
|
||||
<a id="orgd3a9cf9"></a>
|
||||
<a id="figure--fig:morrison16-solenoid"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_solenoid.svg" caption="Figure 7: The \\(H\\) field around a solenoid" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_solenoid.svg" caption="<span class=\"figure-number\">Figure 7: </span>The \\(H\\) field around a solenoid" >}}
|
||||
|
||||
|
||||
### Faraday's law and the induction field {#faraday-s-law-and-the-induction-field}
|
||||
|
||||
When a conducting coil is moved through a magnetic field, a voltage appears at the open ends of the coil.
|
||||
This is illustrated in Figure [8](#org4b2f5c1).
|
||||
This is illustrated in Figure [8](#figure--fig:morrison16-voltage-moving-coil).
|
||||
The voltage depends on the number of turns in the coil and the rate at which the flux is changing.
|
||||
|
||||
<a id="org4b2f5c1"></a>
|
||||
<a id="figure--fig:morrison16-voltage-moving-coil"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_voltage_moving_coil.svg" caption="Figure 8: A voltage induced into a moving coil" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_voltage_moving_coil.svg" caption="<span class=\"figure-number\">Figure 8: </span>A voltage induced into a moving coil" >}}
|
||||
|
||||
The magnetic field has two measured.
|
||||
The \\(H\\) or magnetic field that is proportional to current flow.
|
||||
@@ -232,14 +230,13 @@ The inverse is also true.
|
||||
### The definition of inductance {#the-definition-of-inductance}
|
||||
|
||||
<div class="definition">
|
||||
<div></div>
|
||||
|
||||
Inductance is defined as the ratio of magnetic flux generated per unit current.
|
||||
The unit of inductance if the henry.
|
||||
|
||||
</div>
|
||||
|
||||
For the coil in Figure [7](#orgd3a9cf9):
|
||||
For the coil in Figure [7](#figure--fig:morrison16-solenoid):
|
||||
|
||||
\begin{equation} \label{eq:inductance\_coil}
|
||||
V = n^2 A k \mu\_0 \frac{dI}{dt} = L \frac{dI}{dt}
|
||||
@@ -247,12 +244,12 @@ V = n^2 A k \mu\_0 \frac{dI}{dt} = L \frac{dI}{dt}
|
||||
|
||||
where \\(k\\) relates to the geometry of the coil.
|
||||
|
||||
Equation \eqref{eq:inductance_coil} states that if \\(V\\) is one volt, then for an inductance of one henry, the current will rise at the rate of one ampere per second.
|
||||
Equation <eq:inductance_coil> states that if \\(V\\) is one volt, then for an inductance of one henry, the current will rise at the rate of one ampere per second.
|
||||
|
||||
|
||||
### The energy stored in an inductance {#the-energy-stored-in-an-inductance}
|
||||
|
||||
One way to calculate the work stored in a magnetic field is to use Eq. \eqref{eq:inductance_coil}.
|
||||
One way to calculate the work stored in a magnetic field is to use Eq. <eq:inductance_coil>.
|
||||
The voltage \\(V\\) applied to a coil results in a linearly increasing current.
|
||||
At any time \\(t\\), the power \\(P\\) supplied is equal to \\(VI\\).
|
||||
Power is the rate of change of energy or \\(P = d\bm{E}/dt\\) where \\(\bm{E}\\) is the stored energy in the inductance.
|
||||
@@ -263,7 +260,6 @@ We then have the stored energy in an inductance:
|
||||
\end{equation}
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
An inductor stores field energy.
|
||||
It does not dissipate energy.
|
||||
@@ -275,7 +271,6 @@ The movement of energy into the inductor thus requires both an electric and a ma
|
||||
This is due to the Faraday's law that requires a voltage when changing magnetic flux couples to a coil.
|
||||
|
||||
<div class="exampl">
|
||||
<div></div>
|
||||
|
||||
Consider a 1mH inductor carrying a current of 0.1A.
|
||||
The stored energy is \\(5 \times 10^{-4} J\\).
|
||||
@@ -309,7 +304,6 @@ In a typical circuit, conductor carrying current, the average electron velocity
|
||||
## Digital Electronics {#digital-electronics}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This chapter shows that both electric and magnetic field are needed to move energy over pairs of conductors.
|
||||
The idea of transporting electrical energy in field is extended to traces and conducting planes on printed circuit boards.
|
||||
@@ -415,7 +409,6 @@ Radiation occurs at the leading edge of a wave as it moves down the transmission
|
||||
## Analog Circuits {#analog-circuits}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This chapter treats the general problem of analog instrumentation.
|
||||
The signals of interest are often generated while testing functioning hardware.
|
||||
@@ -451,7 +444,6 @@ There are many transducers that can measure temperature, strain, stress, positio
|
||||
The signals generated are usually in the milli-volt range and must be amplified, conditioned, and then recorded for later analysis.
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
It can be very difficult to verify that the measurement is valid.
|
||||
For example, signals that overload an input stage can produce noise that may look like signal.
|
||||
@@ -459,7 +451,6 @@ For example, signals that overload an input stage can produce noise that may loo
|
||||
</div>
|
||||
|
||||
<div class="definition">
|
||||
<div></div>
|
||||
|
||||
1. **Reference Conductor**.
|
||||
Any conductor used as the zero of voltage.
|
||||
@@ -485,39 +476,39 @@ For example, signals that overload an input stage can produce noise that may loo
|
||||
|
||||
### The basic shield enclosure {#the-basic-shield-enclosure}
|
||||
|
||||
Consider the simple amplifier circuit shown in Figure [9](#org3286d62) with:
|
||||
Consider the simple amplifier circuit shown in Figure [9](#figure--fig:morrison16-parasitic-capacitance-amp) with:
|
||||
|
||||
- \\(V\_1\\) the input lead
|
||||
- \\(V\_2\\) the output lead
|
||||
- \\(V\_3\\) the conducting enclosure which is floating and taken as the reference conductor
|
||||
- \\(V\_4\\) a signal common or reference conductor
|
||||
|
||||
Every conductor pair has a mutual capacitance, which are shown in Figure [9](#org3286d62) (b).
|
||||
The equivalent circuit is shown in Figure [9](#org3286d62) (c) and it is apparent that there is some feedback from the output to the input or the amplifier.
|
||||
Every conductor pair has a mutual capacitance, which are shown in Figure [9](#figure--fig:morrison16-parasitic-capacitance-amp) (b).
|
||||
The equivalent circuit is shown in Figure [9](#figure--fig:morrison16-parasitic-capacitance-amp) (c) and it is apparent that there is some feedback from the output to the input or the amplifier.
|
||||
|
||||
<a id="org3286d62"></a>
|
||||
<a id="figure--fig:morrison16-parasitic-capacitance-amp"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_parasitic_capacitance_amp.svg" caption="Figure 9: Parasitic capacitances in a simple circuit. (a) Field lines in a circuit. (b) Mutual capacitance diagram. (b) Circuit representation" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_parasitic_capacitance_amp.svg" caption="<span class=\"figure-number\">Figure 9: </span>Parasitic capacitances in a simple circuit. (a) Field lines in a circuit. (b) Mutual capacitance diagram. (b) Circuit representation" >}}
|
||||
|
||||
It is common practice in analog design to connect the enclosure to circuit common (Figure [10](#org9f3c9db)).
|
||||
It is common practice in analog design to connect the enclosure to circuit common (Figure [10](#figure--fig:morrison16-grounding-shield-amp)).
|
||||
When this connection is made, the feedback is removed and the enclosure no longer couples signals into the feedback structure.
|
||||
The conductive enclosure is called a **shield**.
|
||||
Connecting the signal common to the conductive enclosure is called "**grounding the shield**".
|
||||
This "grounding" usually removed "hum" from the circuit.
|
||||
|
||||
<a id="org9f3c9db"></a>
|
||||
<a id="figure--fig:morrison16-grounding-shield-amp"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_grounding_shield_amp.svg" caption="Figure 10: Grounding the shield to limit feedback" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_grounding_shield_amp.svg" caption="<span class=\"figure-number\">Figure 10: </span>Grounding the shield to limit feedback" >}}
|
||||
|
||||
Most practical circuits provide connections to external points.
|
||||
To see the effect of making a _single_ external connection, open the conductive enclosure and connect the input circuit common to an external ground.
|
||||
Figure [11](#orgc4242ae) (a) shows this grounded connection surrounded by an extension of the enclosure called the _cable shield_.
|
||||
Figure [11](#figure--fig:morrison16-enclosure-shield-1-2-leads) (a) shows this grounded connection surrounded by an extension of the enclosure called the _cable shield_.
|
||||
A problem can be caused by an incorrect location of the connection between the cable shield and the enclosure.
|
||||
In Figure [11](#orgc4242ae) (a), the electromagnetic field in the area induces a voltage in the loop and a resulting current to flow in conductor (1)-(2).
|
||||
This conductor being the common ground that might have a resistance \\(R\\) or \\(1\,\Omega\\), this current induced voltage that it added to the transmitted signal.
|
||||
In Figure [11](#figure--fig:morrison16-enclosure-shield-1-2-leads) (a), the electromagnetic field in the area induces a voltage in the loop and a resulting current to flow in conductor (1)-(2).
|
||||
This conductor being the common ground that might have a resistance \\(R\\) or \\(1\\,\Omega\\), this current induced voltage that it added to the transmitted signal.
|
||||
Our goal in this chapter is to find ways of keeping interference currents from flowing in any input signal conductor.
|
||||
To remove this coupling, the shield connection to circuit common must be made at the point, where the circuit common connects to the external ground.
|
||||
This connection is shown in Figure [11](#orgc4242ae) (b).
|
||||
This connection is shown in Figure [11](#figure--fig:morrison16-enclosure-shield-1-2-leads) (b).
|
||||
This connection keeps the circulation of interference current on the outside of the shield.
|
||||
|
||||
There is only one point of zero signal potential external to the enclosure and that is where the signal common connects to an external hardware ground.
|
||||
@@ -527,7 +518,6 @@ If there is an external electromagnetic field, there will be current flow in the
|
||||
A voltage gradient will couple interference capacitively to the signal conductors.
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
An input circuit shield should connect to the circuit common, where the signal common makes its connection to the source of signal.
|
||||
Any other shield connection will introduce interference.
|
||||
@@ -535,16 +525,15 @@ Any other shield connection will introduce interference.
|
||||
</div>
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
Shielding is not an issue of finding a "really good ground".
|
||||
It is an issue of using the _right_ ground.
|
||||
|
||||
</div>
|
||||
|
||||
<a id="orgc4242ae"></a>
|
||||
<a id="figure--fig:morrison16-enclosure-shield-1-2-leads"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_enclosure_shield_1_2_leads.png" caption="Figure 11: (a) The problem of bringing one lead out of a shielded region. Unwanted current circulates in the signal lead 2. (b) The \\(E\\) field circulate current in the shield, not in the signal conductor." >}}
|
||||
{{< figure src="/ox-hugo/morrison16_enclosure_shield_1_2_leads.png" caption="<span class=\"figure-number\">Figure 11: </span>(a) The problem of bringing one lead out of a shielded region. Unwanted current circulates in the signal lead 2. (b) The \\(E\\) field circulate current in the shield, not in the signal conductor." >}}
|
||||
|
||||
|
||||
### The enclosure and utility power {#the-enclosure-and-utility-power}
|
||||
@@ -554,9 +543,9 @@ The power transformer couples fields from the external environment into the encl
|
||||
The obvious coupling results from capacitance between the primary coil and the secondary coil.
|
||||
Note that the secondary coil is connected to the circuit common conductor.
|
||||
|
||||
<a id="org5995e31"></a>
|
||||
<a id="figure--fig:morrison16-power-transformer-enclosure"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_power_transformer_enclosure.png" caption="Figure 12: A power transformer added to the circuit enclosure" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_power_transformer_enclosure.png" caption="<span class=\"figure-number\">Figure 12: </span>A power transformer added to the circuit enclosure" >}}
|
||||
|
||||
|
||||
### The two-ground problem {#the-two-ground-problem}
|
||||
@@ -566,9 +555,9 @@ Note that the secondary coil is connected to the circuit common conductor.
|
||||
|
||||
The basic analog problem is to condition a signal associated with one ground reference potential and transport this signal to a second ground reference potential without adding interference.
|
||||
|
||||
<a id="org3228c82"></a>
|
||||
<a id="figure--fig:morrison16-two-ground-problem"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_two_ground_problem.svg" caption="Figure 13: The two-circuit enclosures used to transport signals between grounds" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_two_ground_problem.svg" caption="<span class=\"figure-number\">Figure 13: </span>The two-circuit enclosures used to transport signals between grounds" >}}
|
||||
|
||||
|
||||
### Strain-gauge instrumentation {#strain-gauge-instrumentation}
|
||||
@@ -582,9 +571,9 @@ The basic analog problem is to condition a signal associated with one ground ref
|
||||
|
||||
### The basic low-gain differential amplifier (forward referencing amplifier) {#the-basic-low-gain-differential-amplifier--forward-referencing-amplifier}
|
||||
|
||||
<a id="org4f33add"></a>
|
||||
<a id="figure--fig:morrison16-low-gain-diff-amp"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_low_gain_diff_amp.svg" caption="Figure 14: The low-gain differential amplifier applied to the two-ground problem" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_low_gain_diff_amp.svg" caption="<span class=\"figure-number\">Figure 14: </span>The low-gain differential amplifier applied to the two-ground problem" >}}
|
||||
|
||||
|
||||
### Shielding in power transformers {#shielding-in-power-transformers}
|
||||
@@ -599,7 +588,6 @@ The basic analog problem is to condition a signal associated with one ground ref
|
||||
### Signal flow paths in analog circuits {#signal-flow-paths-in-analog-circuits}
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
Here are a few rule that will help in analog board layout:
|
||||
|
||||
@@ -625,13 +613,13 @@ Here are a few rule that will help in analog board layout:
|
||||
|
||||
### Feedback theory {#feedback-theory}
|
||||
|
||||
<a id="org4a09d89"></a>
|
||||
<a id="figure--fig:morrison16-basic-feedback-circuit"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_basic_feedback_circuit.svg" caption="Figure 15: The basic feedback circuit" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_basic_feedback_circuit.svg" caption="<span class=\"figure-number\">Figure 15: </span>The basic feedback circuit" >}}
|
||||
|
||||
<a id="orgf414d06"></a>
|
||||
<a id="figure--fig:morrison16-LR-stabilizing-network"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_LR_stabilizing_network.svg" caption="Figure 16: An LR-stabilizing network" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_LR_stabilizing_network.svg" caption="<span class=\"figure-number\">Figure 16: </span>An LR-stabilizing network" >}}
|
||||
|
||||
|
||||
### Output loads and circuit stability {#output-loads-and-circuit-stability}
|
||||
@@ -667,27 +655,26 @@ If the resistors are replaced by capacitors, the gain is the ratio of reactances
|
||||
This feedback circuit is called a **charge converter**.
|
||||
The charge on the input capacitor is transferred to the feedback capacitor.
|
||||
If the feedback capacitor is smaller than the transducer capacitance by a factor of 100, then the voltage across the feedback capacitor will be 100 times greater than the open-circuit transducer voltage.
|
||||
This feedback arrangement is shown in Figure [17](#org74f6090).
|
||||
This feedback arrangement is shown in Figure [17](#figure--fig:morrison16-charge-amplifier).
|
||||
The open-circuit input signal voltage is \\(Q/C\_T\\).
|
||||
The output voltage is \\(Q/C\_{FB}\\).
|
||||
The voltage gain is therefore \\(C\_T/C\_{FB}\\).
|
||||
Note that there is essentially no voltage at the summing node \\(s\_p\\).
|
||||
|
||||
<div class="important">
|
||||
<div></div>
|
||||
|
||||
A charge converter does not amplifier charge.
|
||||
It converts a charge signal to a voltage.
|
||||
|
||||
</div>
|
||||
|
||||
<a id="org74f6090"></a>
|
||||
<a id="figure--fig:morrison16-charge-amplifier"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_charge_amplifier.svg" caption="Figure 17: A basic charge amplifier" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_charge_amplifier.svg" caption="<span class=\"figure-number\">Figure 17: </span>A basic charge amplifier" >}}
|
||||
|
||||
<a id="orgb9f996c"></a>
|
||||
<a id="figure--fig:morrison16-charge-amplifier-feedback-resistor"></a>
|
||||
|
||||
{{< figure src="/ox-hugo/morrison16_charge_amplifier_feedback_resistor.svg" caption="Figure 18: The resistor feedback arrangement to control the low-frequency response" >}}
|
||||
{{< figure src="/ox-hugo/morrison16_charge_amplifier_feedback_resistor.svg" caption="<span class=\"figure-number\">Figure 18: </span>The resistor feedback arrangement to control the low-frequency response" >}}
|
||||
|
||||
|
||||
### DC power supplies {#dc-power-supplies}
|
||||
@@ -705,7 +692,6 @@ It converts a charge signal to a voltage.
|
||||
## Utility Power and Facility Grounding {#utility-power-and-facility-grounding}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This chapter discusses the relationship between utility power and the performance of electrical circuits.
|
||||
Utility installations in facilities are controller by the NEC (National Electrical Code).
|
||||
@@ -798,7 +784,7 @@ Listed equipment
|
||||
### Neutral conductors {#neutral-conductors}
|
||||
|
||||
|
||||
### \\(k\\) factor in transformers {#k--factor-in-transformers}
|
||||
### \\(k\\) factor in transformers {#k-factor-in-transformers}
|
||||
|
||||
|
||||
### Power factor correction {#power-factor-correction}
|
||||
@@ -858,7 +844,6 @@ Listed equipment
|
||||
## Radiation {#radiation}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
This chapter discusses radiation from circuit boards, transmission lines, conductor loops, and antennas.
|
||||
The frequency spectrum of square waves and pulses is presented.
|
||||
@@ -917,7 +902,6 @@ Simple tools for locating sources of radiation are suggested.
|
||||
## Shielding from Radiation {#shielding-from-radiation}
|
||||
|
||||
<div class="sum">
|
||||
<div></div>
|
||||
|
||||
Cable shields are often made of aluminum foil or tinned copper braid.
|
||||
Drain wires make it practical to connect to the foil.
|
||||
@@ -1033,7 +1017,8 @@ To transport RF power without reflections, the source impedance and the terminat
|
||||
### Shielded and screen rooms {#shielded-and-screen-rooms}
|
||||
|
||||
|
||||
|
||||
## Bibliography {#bibliography}
|
||||
|
||||
<a id="org7a49345"></a>Morrison, Ralph. 2016. _Grounding and Shielding: Circuits and Interference_. John Wiley & Sons.
|
||||
<style>.csl-entry{text-indent: -1.5em; margin-left: 1.5em;}</style><div class="csl-bib-body">
|
||||
<div class="csl-entry"><a id="citeproc_bib_item_1"></a>Morrison, Ralph. 2016. <i>Grounding and Shielding: Circuits and Interference</i>. John Wiley & Sons.</div>
|
||||
</div>
|
||||
|
||||
Reference in New Issue
Block a user