PyVISA & Instrument Control with Python

PyVISA is a Python package that enables you to control all kinds of measurement devices independently of the interface (e.g. GPIB, RS232, USB, Ethernet).

As you might know, the programming of test and measurement (T&M) instruments can be real pain. There are many different protocols, sent over many different interfaces and bus systems (e.g. GPIB, RS232, USB, Ethernet).

For every programming language you want to use, you have to find libraries that support both your device and its bus system.

In order to ease this unfortunate situation, the Virtual Instrument Software Architecture (VISA) specification was defined in the middle of the 90's.

VISA is a standard for configuring, programming, and troubleshooting instrumentation systems comprising GPIB, VXI, PXI, Serial, Ethernet, and/or USB interfaces. Today VISA is implemented on all significant operating systems.

Simply put, computers are often used to communicate with measurement equipment to automate a measurement, and there are many ways to implement this communication.

While it is possible to communicate via the serial ports or USB ports using a low-level computer language, it is usually more convenient to use a high level language such as LabVIEW or Python to communicate with instruments. These languages can then also be used to manipulate the data and display it.

Some instruments implement the Virtual Instrument Software Architecture(VISA) which is a standard that gives the instruments plug-and-play capability. 

Programs that understand VISA (like LabVIEW or Python) can recognize which instruments are connected to the computer and communicate with them.

Usually this communication takes place by sending text strings to the instrument. A common format is called Standard Commands for Programmable Instruments (SCPI).

Anyway, some manufacturers do not follow these standards and it is necessary to install drivers to communicate with their instruments.

Note that for instruments that have a microprocessor and memory, it is often possible to upload a program to the instrument and then tell the instrument to execute this program. Popular programming environments for communicating with and controlling instruments are LabVIEW and Python.

Python is a high level programming language that is suitable for small and large projects. It has a large library, operates on many platforms, and is free to download. To communicate with instruments that support the VISA standard it is easy to use the PyVISA package as it allows you to communicate using a variety of interfaces such as GPIB, RS232, USB.

That is it for now. More to come later ⫸

(info source courtesy - https://www.tugraz.at/home)

Car Audio System & Power Ratings

Obviously, the most popular specification that consumers look at when purchasing a car audio amplifier system is its output power rating.

OK, this quick post is to help you get an overview of what the amplifier power rating means!

Basically, an audio amplifier system takes a small signal input and raises it in voltage and current to drive a low-impedance loudspeaker. Note that the more power you have, the more loudly you can play your car audio system before the signal going to the loud speakers distorts. 

And, the limit of how much power is required is determined by the power handling specifications of the in-car loud speakers ,their cone excursion limits and their distortion characteristics. 

An audio amplifier set up in a lab to measure power is typically connected to a power supply and a set of load resistors. Special test equipments are also used to measure the distortion characteristics of the output signal to determine the point at which you would hear the distortion.

The Consumer Technology Association (CTA) has established a standard for the power and signal-to-noise ratio measurements of car audio amplifiers called CTA-2006-B.

The specification states that power measurements are to be taken with the car amplifier powered with a DC voltage of 14.4V, and the measurement is taken into a specified load (Typically 4Ω) with no more than 1% total harmonic distortion and noise (THD+N) across the entire bandwidth of the amplifier.

Simply put, the audio amplifier must perform as well producing bass as it does high-frequency information, and the specified power rating cannot include large amounts of distortion.

What is the difference between continuous RMS vs. peak power?

And why does it matter? Read this PDF ↗

Finally, this post is just a snip from a BestCarAudio.com Magazine article published in 2019.

This is the LINK to the original article Understanding the Specs – Amplifier Power Ratings ⇱

See you next week ⪫

Ferroresonant Transformer

A Ferroresonant Transformer, also know as constant voltage transformer (CVT) is designed to achieve regulation with non-linear operation. It provides line regulation, reduce harmonics, and is current limiting.

In addition to providing above benefits, it also provides line isolation and some models come built in with additional output transient voltage suppression (TVS) mechanism.

There is no method in a conventional transformer for the regulation of the output against changing input voltages because it is designed to operate on the linear portion of the magnetization curve (below the knee).

A basic ferroresonant transformer consists of a core, a primary winding, two secondary windings - one for the load and one for the capacitor - and a magnetic shunt that separates the primary and secondary windings. The load regulation will be higher because of the inherent internal regulation of the transformer.

In other words, ferroresonant transformer uses a transformer core that is operated in saturation. So, a change of magnitude of flux density is relatively independent of the magnetic flux inside the core. This means, since the transformer core is operated under saturation, small change in input voltage do not cause any significant change in the output voltage.

Note that the secondary circuit of the ferroresonant transformer comprises of a resonant tank circuit. If the resonant tank circuit is not there, the output voltage will be a square wave with high harmonic voltage distortion. By adding the resonant circuit, a quasi-sine wave voltage can be obtained.

To sum-up, ferro-resonant transformer is a special lamination transformer. Sometimes it may be preferred as constant-voltage-transformer (CVT) or voltage stabilizer because it provides a relatively constant output voltage with less distortion using a wide range of input voltages. 

Benefiting from the features of regulated output, quasi-square waveform and wide input voltage range, ferroresonant transformer is widely used in power supply, voltage regulator, lighting, inverter, battery charger and other industrial tools.

In industry, ferroresonant transformers are used in application that could be negatively affected by voltage sags or voltage dips in the power system.

Keep note that a Constant Voltage Normal (CVN) transformer produces a square wave output, while a Constant Voltage Sinusoidal (CVS) transformer produces a sinewave output!

Thanks ◮  https://electroncoil.com https://voltage-disturbance.com https://www.shapellc.com → 

Power NTC Thermistors

This quick post is about Power NTC Thermistors & Inrush Current Limiting!

At the time of powering on an electronic device such as a switch-mode power supply, the device is charged with an instantaneous abnormal current with a high peak.

It is called an inrush current, and without protection, it may destroy a sensitive semiconductor device or have a harmful effect on the service life of a smoothing capacitor.

Power NTC thermistors are used as inrush current limiters (ICLs) to protect circuits of electrical and electronic devices against inrush currents easily and effectively.

Basically, NTC thermistor is a temperature-dependent non-linear resistor that employs special semiconductor ceramics with a negative temperature coefficient (NTC).

An NTC thermistor has a high resistance at room temperature, and when it is energized, it generates heat by itself and the resistance falls as the temperature rises.

With this property, it can be used as a current protection device to limit inrush currents.

See, the manner in which the resistance of an NTC thermistor decreases is related to a constant known in the electronics industry as beta, or ß. Beta is measured in °K.

In a nutshell, Power NTC Thermistors are made of a metal-oxide ceramic material in the form of ceramic discs that help provide protection against damaging inrush currents upon equipment startup and/or switching on.

As such, Power NTC Thermistors are commonly referred to as Inrush Current Limiters (ICLs) and help reduce downstream component damage.

NTC Thermistor General Information - Technical Overview (TDK) PDF ⇲

How to select NTC thermistors for inrush current limiting?

In practice, there are 3 major criteria for selecting the best NTC thermistor inrush current limiter, surge suppressor for an application:

• Rated resistance (R25)
• Maximum permissible continuous current under rated operating conditions (Imax, DC or RMS values for AC)
• Maximum capacitance CT to be switched

Read More & Stay Tuned https://amwei.com/how-to-select-ntc-thermistors-for-inrush-current-limiting/

Intermediate Frequency Transformer (IFT)

In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception.

Intermediate frequencies are used in superheterodyne radio receivers, in which an incoming signal is shifted to an intermediate frequency for amplification before final detection is done.

The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning, resulting in a signal at the difference or beat frequency.

According to Wikipedia, perhaps the most commonly used intermediate frequencies for broadcast receivers are around 455 kHz for AM receivers and 10.7 MHz for FM receivers, some other frequencies can be used in special purpose receivers, though.

IF transformers or IF amplifier transformers are simply tunable inductors, usually with an integral fixed capacitor, and are typically used inside cheaper transistor radios. Mostly they are used as synchronously tuned filters because each stage is coupled by an active device.

In other words, an IF, or Intermediate Frequency, Transformer (IFT) is a tuned air core transformer used in just about all analog Superheterodyne receivers in past and current AM and FM designs.

Intermediate Frequencies (IF) have been standardized on the broadcast bands with 455 kHz used for AM and 10.7 MHz used for FM.

Most Superheterodyne receivers have two or more IFTs to increase signal gain and selectivity (selectivity is the ability of a radio receiver to focus on one broadcast while rejecting others that are close in frequency as the desired one).

Superheterodyne Radios take an incoming broadcast and convert it to an intermediate frequency using a process called Heterodyning.

Heterodyning is used as it is more efficient and cost effective to design a radio frequency (RF) amplifier for a small window of frequencies than to design one efficient across and entire broadcast band.

For the noobs, essentially there are two coils in an IFT usually (but not always) one above the other.

The IFT is tuned to the intermediate frequency (IF) of the radio which is the difference between the tuned signal being received and the local oscillator (LO) in the radio which usually runs at a higher frequency.

So if you are receiving a signal at 1500 kHz, the local oscillator could be running at 1955 kHz. The difference here is 455 kHz and this is what the IFTs will be tuned to. And to some extent, correct tuning of the IFTs will affect the audio signal quality in subtle ways. 

Put another way, in a traditional AM radio where the received signal is in the range 540 kHz to 1650 kHz, the local oscillator (which's in fact a variable frequency oscillator) signal is always a constant 455 kHz higher or 995 kHz to 2105 kHz.

Rather unsurprisingly, vintage medium wave (MW) AM radios often had double tuned IFTs. These old school IFTs do not have taps and therefore are high impedance devices that are intended for vacuum tube (valve) radios.

So, IFTs used in valve radios usually have tuned primary and secondary circuits whereas transistor radios usually have a single tuned circuit.

Therefore, an IFT for use with transistors will have one adjustment (the primary) and an IFT for use with valves will have two adjustments (the primary and the secondary).

More to come soon (hopefully) ◌⇲

(thanks to https://www.electronics-tutorials.com)

Neodymium Disc & Ring Magnets & Magnetization Directions

Neodymium rare earth magnets (NdFeb) vary in shape and size, and the different shapes each have their own corresponding magnetization direction patterns. 

All Neodymium magnets have both a north and south pole.

Becoming familiar with the magnetization direction of your magnets will help you determine which one is best for your project and which way it should be oriented so that it works most effectively.

Note that a magnet is strongest when one of its poles is touching the opposing surface. For example, an axially magnetized disc/ring magnet will work best when one of its fl at faces is flush against the flat opposite-polarity side of another disc or ring magnet.

Disc magnets can be either axially magnetized or diametrically magnetized. Axially magnetized disc magnets have the north and south poles on the large flat surfaces, while diametrically magnetized disc magnets have the north and south poles on the rounded sides.

Likewise, ring magnets can be either axially magnetized or diametrically magnetized. That is, axially magnetized ring magnets have the north and south poles on the flat surfaces, while diametrically magnetized ring magnets have the north and south poles on the rounded side.

Neodymium ring magnet is circular in shape with a hollow center. Besides the conventional axial magnetizing or diametrically magnetizing ring magnets, radially oriented ring magnet (uni-pole magnetized magnet) is also available. 

Note: Neodymium ring magnets are easy to corrode under humid environment and are necessary to cover with a protective coating.

⇲ Main Reference Source https://totalelement.com/blogs/about-neodymium-magnets/neodymium-magnetization-direction

Current Feedback Amplifiers (CFB)

We often misunderstand current feedback amplifiers, although they have been available for many years!

Current Feedback (CFB) operational amplifiers (Op-Amps) have been around for more than 30 years. They were designed for extreme high-speed performance, which Voltage Feedback (VFB) amplifiers could not accomplish at that time. 

CFB amplifiers have one major advantage over VFBs, they maintain their bandwidth over a wide range of signal gain. Note that VFB amplifiers are gain-bandwidth dependent, meaning their bandwidth decreases with increasing signal gain.

In practice, CFB amplifiers are commonly used in high-speed applications while VFB amplifiers are preferably used in precision applications.

Now see the figures below (click image to enlarge):

A VFB amplifier has two symmetrical, high-impedance inputs. The fact that the negative input is high-impedance makes the feedback network, driven by the output voltage VO, operate in Voltage-Source mode.

Here the series source impedance of this voltage source is the parallel circuit of RF and RG. The output of this voltage source is connected to the inverting input, providing the voltage potential, vn, at this pin.

The voltage potential at the non-inverting input, vp, is identical to the signal input voltage VI. Thus, the difference between the two input potentials is an error voltage, ve, that is amplified to generate VO.

However, unlike the VFB amplifier, the CFB amplifier has asymmetric inputs. Internally the non-inverting input connects using a unity-gain buffer to the inverting input. Thus, the non-inverting input exhibits the high impedance of the buffer input, while the inverting input presents the low impedance of the buffer output to the feedback network.

This low input impedance makes the feedback network operate in Current-Source mode. The parallel source impedance of this current source again is the parallel circuit of RF and RG.

During normal operation, the input voltage VI drives a current, ip, into the non-inverting input, and the output of the feedback current source drives a current, in, into the inverting input. The difference between the two input currents is the error current, ie. This error current is driven into an internal high-impedance stage, which results in the output voltage, VO.

To summarize, the major difference between a VFB and a CFB amplifier is the type of input error signal generating the output voltage. A VFB op-amp uses an error voltage while a CFB op-amp uses an error current.

⇲ REFERENCE: RENESAS Application Note AN1993 Rev.0.00, May 31, 2018

OK, current feedback op-amps can be successfully used in a variety of applications. More to come later!

Intelligent Power Module (IPM)

Power semiconductor devices play a significant role in modern power control and drive systems, and one of the most common devices used in these systems is the IPM module.

An IPM (Intelligent Power Module) is in fact a powerful integrated circuit module used for controlling and driving high-power electronic devices such as AC motor drivers, inverters, frequency converters, etc. It is a highly integrated semiconductor device that typically includes multiple functional modules such as power switches, drive circuits, protection circuits, and control circuits.

So, IPM is an acronym for Intelligent Power Module, a general term for modules that combine discrete semiconductors such as IGBTs and MOSFETs with driving circuits, protection circuits, and other circuitry.

Since the driving conditions and protection functions are optimized for the built-in power devices, and because they are easy to use, they are called Intelligent Power Modules (IPMs),

Keep note at this point that the key difference between Power Modules and IPMs is that a power module incorporates multiple discrete semiconductors in a single package, but a driving circuit and a protection circuit must be provided separately.

That is, an IPM typically includes a power MOSFET, IGBT, or SiC(Silicon Carbide) switch device, as well as a drive circuit for controlling the conduction and cutoff of these switch devices.

In addition, IPM modules often integrate features such as power supply circuits, current and voltage sensors, over-temperature protection, and short-circuit protection.

These functions provide comprehensive protection measures to ensure the safety and reliability of high-power electronic devices.

As an example of a widely used IPM, here is the PDF DATASHEET ↗ of a 600V IGBT IPM.

The aforementioned IPM (BM63563S-VA/-VC) is an intelligent power module (3phase DC/AC Inverter) composed of gate drivers, bootstrap diodes, IGBTs, flywheel diodes. Low saturation voltage IGBTs optimized for low speed switching drive (to 6kHz) such as a compressor is adopted.

As an aside, the HSDIP25 is a long pin type package for intelligent power modules (IPMs). See this PDF ↗ for more IGBT-IPM details from ROHM Semiconductor.

To be continued ⪫⪫⪫

Audio Filters Guide

An audio filter is one of the most essential building blocks of audio electronics, and it is a processing technique used to manipulate sound signals in a specific manner.

An audio filter can modify the frequency response of an audio signal, change its tone or texture, remove unwanted noise or artifact, or enhance specific aspects of the audio. 

In essence, an audio filter is a hardware device or software program that is designed to filter the frequency characteristics of an audio signal. The basic idea behind a filter is exactly as it sounds - they filter some frequencies out, and let others remain. 

With audio filters, we can filter specific frequencies, or whole groups of frequencies, known as bands. You can see them everywhere in the audio world, but to use them, you have to know how they work, and which filters are best for each purpose.

First off note that there are many different types of audio filters, including low-pass filters, high-pass filters, band-pass filters, and notch filters, among others.

Each type of filter has its own unique characteristics and can be used for different purposes in audio processing.

⪫ A low-pass filter (LPF) is a type of audio filter that allows low frequency signals to pass through, but blocks or attenuates high frequency signals.

⪫ A high-pass filter (HPF) is a type of audio filter that allows high frequency signals to pass through, but blocks or attenuates low frequency signals.

⪫ A band-pass filter (BPF) is a type of audio filter that allows a specific range of frequencies (also known as a band) to pass through, while blocking frequencies below and above this range.

⪫ A band-stop filter is a filter that allows us to let everything pass, while selecting a band of frequencies to remove

⪫ A notch filter is a filter that allows us to remove or reduce a specific frequency (this is similar to the band-stop filter, but it focuses on a targeted frequency precisely).

In other words:

⪫ A low-pass filter passes low frequencies and cuts or filters out high frequencies.

⪫ A high-pass filter is useful to cut low frequencies, so it  is sometimes called a low cut ( the same way a low-pass is occasionally called a high cut).

⪫ A band-pass filter can be useful for isolating a particular range of frequencies in an audio signal, or for shaping the tonal character of a sound by boosting or cutting a specific range of frequencies.

⪫ A band-stop filter is the opposite of a band-pass filter.

⪫ A notch filter is similar to a band-stop filter. It is called a notch filter because it creates a notch (or dip) in the frequency response at the target frequency, effectively attenuating or cutting that frequency.

Now you’ll know what common audio filters are and how to use them.

Wikipedia https://en.wikipedia.org/wiki/Audio_filter

Well, stay tuned to get more helpful pointers for creatively shaping the tone of your sounds in sound design.

Spoiler Alert ⨶  There are thousands of ways you could apply audio filters creatively!

Reference Source - https://www.native-instruments.com/en/

Ring Radiator (Audio)

Ring Radiator is a radical revolution in domestic audio technology.

A ring radiator, also known as a ring speaker, is a type of tweeter that differs from traditional high-frequency transducer, which differs from the traditional dome loudspeakers.

Its distinctive design incorporates the utilization of a ring-shaped diaphragm in place of the conventional dome.

The design also allows for an even distribution of sound, which results in a more natural and detailed sound quality.

In Hi-Fi audio systems where sound quality is of primary importance, the ring radiator will prove to be an adequate solution.

It is a characteristic of traditional tweeters that they are prone to generate distortion at higher volume levels.

But the ring radiator’s distinctive design ensures minimal distortion, thus facilitating a more natural sound even at high volumes.

Thus, the capacity of the device to reproduce treble without distortion permits users to enjoy music of the highest quality.

Now see the Scan-Speak Ring Radiator Tweeters Datasheet PDF

The area of audio technology is perpetually engaged in an ongoing pursuit of excellence.

Audiophiles and those with a keen interest in audio and music are consistently seeking out equipment that will provide them with the optimal listening experience.

One of the most recent developments in this field is the ring radiator.

Here you will see an an article that examines the nature of a ring radiator, the advantages of utilizing such a device, and the reasons why a domestic audio system comprising one is capable of producing a superior audio experience which sounds better than ever before ↓

https://dioraacoustics.com/en/ring-radiator-a-radical-revolution-in-domestic-audio-technology/

Quick Guide to Trimmer Capacitors

This post is a quick guide to trimmer capacitors!

As you already know, trimmer capacitor is a variable capacitor which can be used to trim the performance of both active and passive circuits.

Trimmer capacitors typically cover a capacitance range of 1 pF to 2 pF but can extend up to 200 pF or more.

While a fixed capacitor is essentially two fixed metal plates that hold charge, in a trimmer capacitor the plates (the stator and rotator plates) are either adjusted in distance from each other or the amount of exposed area is shifted to change the amount of capacitance.

Also, like a fixed capacitor, some form of dielectric such as air, ceramic, glass, polytetrafluoroethylene, or sapphire is used as electrical insulation between the plates or other metalized surfaces.

Further Reading ↗ https://blog.knowlescapacitors.com/blog/your-quick-guide-to-trimmer-capacitor-selection-part-1

Note that there are a variety of trimmer types available. What is important is choosing the right one for each application.

Each of the trimmer capacitor types has its positive and negative aspects, and some are better suited to particular circuits than others. Understanding how to make the most of a trimmer capacitor involves an array of choices in packages, dielectric materials, and performance parameters.

Trimmers are available in precision Multi-Turn and Half/Single turn formats. Ceramic half-turn trimmers are the most common types as they are well suited to applications in which low cost and small size are the overriding concerns.

At higher frequencies, a multi-turn trimmer with Air, Teflon or Sapphire dielectrics provides the best solution. In an air trimmer, capacitance is created by a movable set of concentric metal rings fitted into a fixed set of parallel rings. As the rings mesh, capacitance increases. A fine-thread screw provides many turns of resolution for setting to the exact desired value.

Learn More ↗ https://www.mwrf.com/technologies/components/article/21846602/evaluating-trimmer-capacitor-choices

And see the datasheet of muRata TZC3 series ceramic trimmer capacitors in PDF

Fast Recovery Diode

A fast recovery diode (FRD) is a type of diode with a short reverse recovery time (Trr) that is used for high-frequency switching!

The structure and function of an FRD is the same as that of a rectifier diode.

Rectifier diodes are used for low-frequency applications below 500 Hz, whereas FRDs are used for high-frequency switching from a few kHz to 100 kHz.

Therefore, the reverse recovery time (Trr) of the diode characteristic, which is important for high-speed switching, is short. FRDs are also referred to as S-FRDs, HEDs, etc. according to the Trr value.

The trr of a general rectifier diode is several μs to several tens of μs. On the other hand, Trr of an FRD is several tens of ns to several hundred ns and is about 1/100 of that of the rectifier diode. It is used in switching power supplies, inverters, dc/dc converters, etc.

In other words, FRD is a diode with a p-n junction is designed to make the reverse recovery time (Trr) smaller and is also called a high-speed diode.

Compared to general rectifying diodes (standard recovery diodes), the Trr is 2 to 3 digits smaller because the FRD is designed with a switching power supply to rectify high frequencies of tens of kHz or hundreds of kHz.

So, FRD stands for fast recovery diode. Such a high-speed diode offers high-speed support and generally have a Trr of approximately 50 to 100 ns.

Note, with a VF (forward voltage) of approximately 1.5 V, it is rather large when compared to general rectifying diodes (the smaller the reverse recovery time is made, the larger the forward voltage becomes).

On the other hand, general rectifier diodes are low-speed p-n diodes with large trr and small VF. These diodes are designed for commercial frequencies such as 50/60 Hz, and are not used in fast switching circuits.

Even among the fast recovery diodes, Ultra Fast Recovery Diode is a component designed specifically for speed. In this case, the Trr is approximately 25 ns, which is extremely small, but the VF is quite large at 3 to 3.6 V.

Now see the PDF datasheet of the FR107 1A Fast Recovery Diode https://www.diodes.com/assets/Datasheets/products_inactive_data/ds26001.pdf

To sum-up, diodes can be subdivided into two main classes: Rectifier diodes (standard recovery) and fast diodes.

Rectifier diodes are generally used for conversion of alternating current to direct current (AC to DC). While optimized for low conduction losses, rectifier diodes withstand only moderate dynamic stress in transition from conducting to the blocking state.

Fast diodes, on the other hand, are companion devices to switches in DC to AC conversion. Fast diodes are optimized to accept high dynamic stress (fast transition from conducting to blocking state). However, they generally have higher conduction losses than rectifier diodes.

(thanks to https://www.shindengen.com/ , https://www.hitachienergy.com/in/en , &  https://www.global.toshiba/ww/top.html)

Kelvin–Varley Divider

Kelvin-Varley Voltage Divider, named after its inventors William Thomson, 1st Baron Kelvin and Cromwell Fleetwood Varley, is an electronic circuit used to generate an output voltage as a precision ratio of an input voltage, with several decades of resolution.

The Kelvin Varley Voltage Divider may be thought of as being equivalent to a digital potentiometer, except that it has an additional, variable resistance in series with the wiper arm (see the circuit model figure below).

In effect, the Kelvin–Varley divider is an electromechanical precision digital-to-analog converter, and it is used for precision voltage measurements in calibration and metrology laboratories. It can achieve resolution, accuracy and linearity of 0.1 ppm. 

The conventional voltage divider - Kelvin divider - uses a tapped string of resistors connected in series. The fundamental disadvantage of this architecture is that resolution of 1 part in 1000 would require 1000 precision resistors.

To overcome this limitation, the Kelvin–Varley divider uses an iterated scheme whereby cascaded stages consisting of eleven precision resistors provide one decade of resolution per stage.

Cascading three stages, for example, therefore permits any division ratio from 0 to 1 in increments of 0.001 to be selected. Each stage of a Kelvin–Varley divider consists of a tapped string of equal value resistors. See Wikipedia ↗

In practice, if you want 10 steps you need 11 resistors. But by placing a second resistor divider of 11 resistors over two resistors of the tap of choice of the first, you can divide that step into 10 steps again. 

So you already have a resolution of 100 steps with 22 resistors. In essence, you can continue like this infinitely and make incredibly small but also very precise steps. The last string is, what is called, a normal Kelvin Divider.

Below is the basic circuit of a 4-Decade Kevin-Varley Voltage Divider (click on image to enlarge).

Note that in a typical KVD design, each stage provides a decade of resolution and requires only 11 precision resistors. Cascading 3 stages permits any division ratio from 0 to 1 in increments of 0.001 (i.e. resolution of 1 part in 1000).

Now see the three-terminal, Kelvin-Varley Voltage Divider KVD-500 with thumbwheel switches suitable for use in voltage and current dividers for calibration and linearity testing.

Well, comments and corrections to our understanding are always welcome. See you soon!

Moisture Sensitivity Level (MSL) & Popcorn Effect

MSL (Moisture Sensitivity Level) is an electronic standard which is established by JEDEC for the time period in which a moisture sensitive device can be exposed to ambient room temperature.

That is, short for Moisture Sensitivity Level, MSL is a JEDEC (Joint Electron Device Engineering Council) standard established for the purpose of preventing device failure due to volumetric expansion of atmospheric moisture introduced into the resin package of semiconductor devices during reflow.

Note that a semiconductor components with resin-sealed package could be damaged during SMD reflow when moisture was trapped inside the component expands.

And, according to the aforementioned JEDEC standard, there are eight levels of moisture sensitivity as shown in the below table.

Simply put, Moisture Sensitivity Level (MSL) defines how sensitive components are to moisture. Lower MSL levels allow manufacturers a wider processing window; reducing inventory & processing costs.

Popcorn Effect: The popcorn effect is when an IC pops because the moisture inside the package expands in the reflow process. As a result of this expansion the substrate, the die, or the wire bonds could be damaged. 

Note that when the antistatic bag is opened and the IC is exposed to ambient conditions, the moisture in the air is trapped inside the device. This means that during the reflow process, this moisture expands and can damage the device. The damage is often invisible and requires X-ray equipment to conduct a proper analysis.

To avoid the Popcorn Effect, you can simply bake the device and seal it in a hermetically sealed antistatic bag. If the device was exposed to moisture, re-bake it and assemble the device within the allowed exposure time (the baking is driving all the moisture out of the device).

Next figure shows an Xbox 360 graphical processing unit that was desoldered from an Xbox 360 motherboard (https://commons.wikimedia.org/wiki/File:PopcornBGA.jpg).

This photograph shows the risks of desoldering ball-grid array components without proper procedures. 

Here you can see that moisture in the circuit board turned to steam when it was subjected to intense heat. This produces the so-called Popcorn Effect.

You can prevent this by using a fast-acting solvent such as methyl ethyl ketone as well as preheating the circuit board using an oven.

Well, we will be providing more updates in due course ⪫

Found an error? Something else is just not right? Let us know! Leave a comment below!

Banana Plugs Guide

Popular test instruments and test accessories such as leads and cables use banana connectors.

Banana plugs are spring-loaded, single-wire electrical test connectors used for joining wire to electrical equipment or electrical circuit boards.

A banana plug is considered a male connector and is called a banana because of its unique contact tip.

The banana plug is a cylindrical pin that has metal-leaves that bulge outward to produce a strong connectivity contact (snug fit) in a socket to prevent the pin from disconnecting or falling out.

Banana connectors come in two forms, a banana plug or a banana socket (often referred to as a banana jack).

From Wikipedia, a banana connector (commonly banana plug for the male, banana jack or socket for the female) is a single-wire (one conductor) electrical connector used for joining wires to equipment.

The term 4 mm connector is also used, especially in Europe, although not all banana connectors will mate with 4 mm parts, and 2 mm banana connectors exist. Various styles of banana plug contacts exist, all based on the concept of spring metal applying outward force into the unsprung cylindrical jack to produce a snug fit with good electrical conductivity. 

OK, as with all things, there are tons of banana plugs out there offering different combinations and styles or features used for testing equipment and other applications.

And, here is an E-Z HOOK guide to what those banana plug features are, when to use them, and which part is compatible for your specific testing requirements » https://e-z-hook.com/blog-guide-to-banana-plugs/ 

Back-Pinning Probe

A test instrument includes a set of probes. Here we will look at back-pinning probes!

In a back-pinning probe, also know as back probe, its needle is made to push into some type of connectors from the back, making it possible to measure while the connector is connected. 

These probes are essential for probing today’s small, fragile connectors. Since a back-pinning probe is very sharp, it slides past connector seals with ease.

Thus these nifty little needle probes are the perfect electronic accessory when a quick and easy test connection needs to be made without piercing the wire insulation.

Another probe in this category is the Piercing Probe (see below).

The trick is that a tin needle can cut through the isolation and contact the conductor inside. When the probe is removed the hole will basically close itself. This makes it possible to measure on wires without stripping or cutting it and without locating the ends of the wire.

The small diameter and extra sharp pin of a piercing probe (insulation piercing probe) makes it ideal for piercing the insulation on small gauge wires where traditional piercing tools might cause damage.

Generally, a piercing probe has a needle or multiple needles that pierce the wires outer insulation jacket to access the wires internal conductor for testing. By activating the needle(s) upon wire contact, diagnostic testing is able to occur as an instant connection is created to the test and measurement instrument.

Below you can see the image of Pico Technology's Back-Pinning Probe Set ⪫

Note that back-pinning probes and piercing probes are mostly for automotive electric/electronic system diagnosis.

These special probes obviously make non-invasive testing perfect for hard to reach wires and also eliminates the time consuming and destructive nature of strip or cutting wire to access the conductor for testing.

Further Info ⪫ https://e-z-hook.com/blog-guide-to-back-probe-connectors/

More on this later. Thanks for reading!