Tools

10:1 probes are the industry standard. Almost all oscilloscopes have an input impedance of \(1M\Omega\) when looking into the connector on the front panel of the scope.

Capacitance increases when you go from 10:1 to 1:1. e.g. a 10:1 passive probe may have 10pF of capacitance while an equivalent 1:1 probe may have approx. 100pF. You also lose some input resistance, e.g. it drops from \(10M\Omega\) to \(1M\Omega\).

1:1 probes can be good for measuring small levels of noise as they effectively increase the minimum resolution of the oscilloscope by 10 (compared to a 10:1 probe).

Some scope probes allow you to adjust the probes compensation.

Without the variable capacitor, the resistance of the probe combined with the resistance and capacitance of the scope will create a low-pass filter that will greatly distort high frequency measurements. The variable capacitor is added in parallel with the \(9M\Omega\) probe resistance so that there is both a resistive and capacitive potential divider. The capacitance is then adjusted so that both the resistor divider and capacitor divider have the same division ratio. This ensures the response of the probe is flat across the frequencies of interest.

I have never had great success using the maths functions on a scope to measure differential signals (by using two single-ended inputs and subtracting one from the other).

Typically, voltage measurements are done at the highest-impedance achievable (\(>1M\Omega\)) by the multimeter so that the multimeter does not effect the circuit it is measuring. However, this can sometimes lead to "ghost voltages". This is when a real but high-impedance voltage is present on a circuit, normally due to the circuit picking up noise from near-by circuits via phenomenon such as capacitive coupling. This voltage, although real, is misleading as it does not represent the voltage a load (or person getting a shock) would actually see. For this reason these voltages are called ghost voltages.

Some newer digital multimeters come with a low impedance voltage measurement mode to ignore these ghost voltages. This is especially useful for when working with mains power (115/240VAC) and trying to determine if a voltage on a wire is a significant danger or not. Examples of multimeters which have a low-impedance voltage measurement setting include the Fluke 117 Digital Multimeter.

Older, analogue multimeters are not as susceptible to the ghost voltage problem as they typically have a lower impedance when measuring voltages, normally around \(10k\Omega\).

Low-impedance mode should not be used when working with sensitive, small-signal circuitry. The low-impedance of the multimeter might draw enough current to disrupt the circuit and will give you incorrect readings.

Saleae is probably the most expensive well-known logic analyzer brand. As of April 2020, the 8-channel, 500MS/s (Samples/second), 100MHz, USB3.0 Saleae logic analyzer (the Logic Pro 8) will cost USD$699, which is quite a lot of money for JUST a logic analyzer.

DreamSourceLab provides the DSView software for viewing the digital signals from the DSLogic series of logic analysers. DSView is compatible with Windows, MacOS and Linux. It uses the sigrok project to provide all of the protocol decoders and therefore supports many of the protocols listed on https://sigrok.org/wiki/Protocol_decoders.

Whilst a setup .exe is provided for Windows and a .dmg for MacOS, no pre-built executables are provided for Linux, and you have to build yourself from the source code. Easy instructions are provided in the INSTALL text file.

The TekBox TBOH02 DC load is a great, simple, low-cost DC load. It is self-powered, meaning it powers itself from the energy dissipated via the "load" it pretends to be. 25W continuous power dissipation with no fan, 100W with fan. The advantage of it being an analogue, self-powered load means that there will be no digital/PSU/control-circuitry noise superimposed onto the measurements you are making.

This device is open-source hardware (design is based of https://www.edn.com/precision-active-load-operates-as-low-as-2v/, however EDN’s link to the PDF/schematics is broken as of 2021-06-22), the full schematics, board files and BOM are provided at https://www.tekbox.com/product/tboh02-self-powered-active-load/. Schematics and board files are in the Eagle file format.

FTDI (Future Technology Devices International Ltd.) is a popular and reputable designer and manufacturer of USB-to-Serial converters. They make a range of ICs for this purpose, as well and manufacturing useful products which use these ICs (such as USB-to-serial cables).

As of 2016, their ICs are commonly found in good quality USB-to-serial hardware (more so than one of their main competitors, Prolific).

USB-to-Serial converters introduce a fair bit of delays into serial communications. and depending on your latency requirements, this may effect your design.

The below image is a screenshot of FTDI RX/TX data captured with a logic analyser. The computer was running Java code which sent an 0x02 response as soon as it received an 0x01 byte.

FTDI provides the Java D2xx API for Android systems. The API is packaged into a file called d2xx.jar and can be downloaded from http://www.ftdichip.com/Android.htm.

Basic information on the driver software can be found at http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_147_Java_D2xx_for_Android.pdf.

CISPR 25 sets limits and procedures for the measurement for EMI in the frequency range of 150kHz to 2.5GHz[3]. Among other utilities, the standard is applicable to vehicles, and it is a popularly referenced standard among automobile electronic design. It specifies the uses of a \(5uH\) LISN when performing EMI measurements, is one of the main reasons you will see \(5uH\) LISN devices available for purchase.

The TexBox TBOH01 (5uH LISN) is a LISN designed to be compliant with CISPR 25, and retails for around US$250.

Digital microscopes are a great tool to have on an electronics workbench. Coupled with a screen, they allow you to look up close at a PCB without having to peer down the sights of a optical microscope.

The Puhui T-962 (and T-962A, T-962C variants) are cheap static desktop reflow soldering ovens.

The T-962A has the same design except is a larger unit and provides and effective soldering area of 300x320mm.

It appears there are "2020 New Versions" of the above reflow ovens which have exhaust pipe brackets added onto the back so you can clamp on a pipe to vent exhaust fumes.

It is known to produce bad-smelling fumes when in use, especially when it is new. This is because the manufacturer uses aluminium tape and masking tape in the unit which is not designed for high temperatures, which melts!!! It is recommended to replace the masking tape with kapton tape after purchase (see the upgrade section below for more info).

Third parties have made "upgrade kits" for these reflow ovens which aim to to provide better thermal control of the soldering process and improve the UI experience. For example, ES Technical provides upgrade packages for both the T-962 and T-962A. UnifiedEngineering redesigned the firmware to run on the existing microcontroller, with the hardware addition of a temperature sensor for cold junction compensation.

Clones? The Atten AT-R3028 looks VERY similar to the T-962.

NETD: Noise Equivalent Temperature Difference: This is the minimum temperature difference that is resolvable by the camera. You could think of this as the sensitivity. It is bad practise to refer to this as the resolution as this will get confused with the pixel (spatial) resolution. NETD of thermal cameras is typically between 100-500mk (100-500m°C). The NETD is measure by pointing the camera at a very stable and uniform black body at a specific temperature. The NETD is the standard deviation of the varying pixel values recorded by the camera over a specific period of time[1].

Most signal generators have a "Load Impedance" setting. Whilst the signal generator almost always has an output of \(50\Omega\), the signal generator will take this load impedance setting into account and generate a voltage that will result in the set peak-to-peak/amplitude at the output.

However, if this load impedance setting is set to say, 50R, but connected to a high-impedance load (for example, connected straight up to the oscilloscope), you will measure twice the expected voltage at the output!

Most heater elements are between 600-1200W. The body material of the heating element is usually ceramic.

Yihua UYUE

Current probes are not cheap! They are significantly more expensive than their voltage-measuring brothers. As of 2016, you can find cheap no-brand ones for US$60-700, and more expensive Tektronics or Keysight Technologies (the new Agilent) current probes for US$1000-8000.

Hall-effect current probes use the hall-effect phenomenon to measure the current travelling through a conductor. Their main advantage over the transformer-based current probes is that they can measure DC currents. However, they do not perform well at higher frequencies (20kHz seems to be a rough upper limit).

The hall-effect sensor is an active sensor, and therefore the probe requires an external power source. This may be provided by an internal replaceable battery (e.g. 9V battery), and external power supply connector, or from the oscilloscope through a specialised connector (this is common on the more expensive, brand specific ones).

Like the AC transformer-based current probes, they require the wire to be inserted into a loop.

A combined AC/DC current probe is the most versatile current measurement probe. Traditionally, it uses a transformer to measure AC current, and a hall-effect sensor to measure DC currents (originally patented by Tektronics). Hall-effect sensors are active sensors, so AD/DC current probes require a power source.

The probes are normally split-core, which allows you to open the probe tip up to inset the wire under test.

AC/DC probes output a voltage which is proportional to the current flowing through the wire under test. This voltage is measured by the oscilloscope and displayed on a current-scaled waveform. High-end current probes which are built for specific oscilloscopes may draw power from the single oscilloscope connection, as well as automatically changing the units on the scope and auto-scaling.

The main advantage is that the measuring device does not need to fully encircle the track/wire under test, and you can design a probe-styled instrument that can measure track/wire current just by bringing the probe tip into close proximity.

Aim has patents around it’s fluxgate magnetometer based current probe, so it might be a while before other manufacturers make similar probes.

The Beehive Electronics probes set contains three H-field probes (100A, 100B, 100C) and one E-field probe (100D). All are non-contact probes.

The magnetic flux density can be calculated for the H-field probes using the equation below:

The scale factors for each of the magnetic probes is given below:

Typically, fluxes are compatible with a broad range of solder compounds, including both leaded and higher-temperature lead-free solders.

Flux activity is a measure of the strength/aggressiveness of the flux in it’s ability to clean metals while soldering. Low activity fluxes are weak fluxes and as usually mild acids. High activity fluxes are strong fluxes and are usually low pH acids.

During the soldering process fumes are released. The amount of fumes increases drastically as flux is used.

It is generally not a good thing to inhale these fumes on a long term basis. Fume extractors can be used to remove the fumes safely.