It is now trivial and non-invasive to measure blood-oxygen saturation SpO2, thanks to LEDs, algorithms, and ICs for pulse oximetry — it’s a very long way from having to draw blood and send it out for assessment. Part 1 of this FAQ discussed the principle of the non-invasive, light-based pulse-oximetry systems for reading blood-oxygen saturation […]
Blood oxygen meters, Part 1: Background and principles
It is now trivial and non-invasive to measure blood-oxygen saturation SpO2, thanks to LEDs, algorithms, and ICs for pulse oximetry — and it’s a very long way from having to draw blood and send it out for assessment. Just a few decades ago, determining the vital medical parameter known as blood oxygen level — formally […]
Why clean PCBs matter, Part 2
The article Why Clean PCBs Matter, Part 1, covers the effects that a dirty Printed Circuit Board can have on electronics, especially those supporting high-frequency signals or sensitive analog components. Keeping a PCB clean begins in assembly when components are preferably soldered to the PCB in a clean environment. Of great importance is the type […]
Why clean PCBs matter, Part I
Printed circuit boards (PCBs) are essential in modern electronics. Dust and other contaminants are more important to watch out for than ever. As components get smaller, the relative size of contaminants is larger, heat is more of an issue with densely packed circuits on modern ICs, and devices operating at high frequencies (~1 GHz and […]
Quartz crystals and oscillators, Part 2: Advanced crystals
Part 1 of this FAQ established the context for the quartz crystal as the core of an oscillator whether used as a system clock or as a frequency-setting element in a tuning circuit. This part looks at the achievable performance, the factors that affect it, and what can be done for highest performance. Q: What […]
Power-supply overvoltage protection, Part 2: Clamps
Part 1 of this FAQ discussed the context of overvoltage protection and crowbars which provide OVP. This part will look at clamps for OVP use. Q: What does the clamp do? A: A clamp conducts just-enough current to maintain the voltage across it at a safe, desired value when the transient is above the clamp’s […]
Power-supply overvoltage protection, Part 1: Crowbars
Engineers who deal with power supplies (as most eventually do) often see the circuit-protection terms “crowbar” and “clamp.” No, there are no references to items purchased at the local hardware store, but they are essential “hardware” elements, meaning autonomous circuit components and functions with no related software. They are used to provide protection to a […]
Quartz crystals and oscillators, Part 1: Crystal basics
An oscillator or clock function is key to nearly all electronic circuits, and in most (but not all) cases, the heart of this oscillator circuit is a tiny piece of quartz, called the crystal blank or slab. It’s easy and commonplace to think of the crystal as a simple component, but as with most components, […]
GPS, Part 2: Implementation
Part 1 of this FAQ looked at the basic principles of the GPS system. Part 2 looks at some hardware circuitry used to implement a GPS receiver as well as the unappreciated role that Einstein’s Theory of Special Relativity plays in providing an accurate GPS. Q What are the key elements of a GPS receiver? […]
GPS, Part 1: Basic principles
The Global Positioning System (GPS) is a worldwide, RF wireless-based system for determining where you are anywhere in the Earth’s surface if there is line-of-sight visibility to at least four of its orbiting satellites. The availability of GPS since its inception a few decades ago has not only enabled products and features which were simply […]
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