Memo: Chemical equilibrium

Some chemical reactions are reversible. The ingredients, or reactants, interact to create products in the forward reaction while the products (ions, chemical compounds, and thermal difference) interact with one another to recreate the reactants in the backward reaction. These reactions are technically neverending although, in practice, the chemical reaction is considered completed when these two opposite processes… Continue reading Memo: Chemical equilibrium


DIY Memo: ESP8266 v12 analog I/O

This is an amendment to the previous ESP8266v7 memo. More specifically, the I/O pins don't behave exactly as described by internet sources. A little bit of background: I was presented with a challenge to read from an analog sensor and send the reading through wifi network to the cloud. This can be accomplished easily using… Continue reading DIY Memo: ESP8266 v12 analog I/O

Memo: AC excitation

All passive sensors discussed so far rely on DC excitation. DC has its charm in simplicity, low cost and fluid integration into existing digital technologies. However, when it comes to analog technologies, AC excitation remains a cornerstone of high-performance circuits employing inductive or capacitive elements. For the most parts, the working principles of passive sensors are the same in either case;… Continue reading Memo: AC excitation

Memo: Strain gauge bridge circuits

As mentioned in the previous memo, strain gauges are vulnerable to temperature effects such as thermoresistive, thermoelectric and self-heating. Some special alloys like Constantan are designed to be self-compensating while others aren't. Those that aren't will require special conditioning circuits utilizing one or more complimentary strain gauges in bridge topology. Three most common bridge circuits… Continue reading Memo: Strain gauge bridge circuits

Memo: Resistive displacement sensors

Displacement sensors (aka position transducers) convert spatial information; linear distance, rotary position, and deformation; into electrical quantities. One family of such sensors are called "encoders" ergo, devices that encode position into a signal. Based on their coordinate system, encoders can be roughly classified into linear encoder (Cartesian coordinate) or rotary encoder (Polar coordinate) classes. The most basic displacement sensors… Continue reading Memo: Resistive displacement sensors

Memo: Signal conditioning

This memo will use resistive sensors to demonstrate some signal conditioning techniques. Resistive sensors are sensors that map a physical quantity such as temperature, light, and stress into a corresponding resistance value on their characteristic curves. This resistance represents the physical quantity being measured and it itself needs to be conditioned and measured in the… Continue reading Memo: Signal conditioning

Memo: Thermoelectric effects

Active sensors require no power source and they produce output signals directly from the measured physical quantity. Active temperature measurement utilizes direct conversion of temperature difference to an electric voltage, a physical process known as thermoelectric effects. Thermoelectric effect is a common name for three separate effects: Seebeck effect, which is the conversion of thermal to… Continue reading Memo: Thermoelectric effects

Memo: Passive thermometers

Sensors are transducers or devices that convert a physical quantity into an electrical quantity. There are two main types of sensors: passive and active sensors. Passive sensors require an external power source (aka, excitation signal) while active sensors don't. For example, a photoresistor (aka photoconductor, aka LDR) is a passive sensor, requiring an input current while… Continue reading Memo: Passive thermometers

Memo: Phase-locked loop

Phased-lock loop (PLL) synchronizes the frequency of output and input signals. The output signal is generated internally as part of the phase-lock loop; specifically from its variable-frequency oscillator (VFO). PLL applications PLLs are primarily used for clock synchronization within IC packages, encompassing the whole or parts of the IC's (signal processing) circuitry within its loop… Continue reading Memo: Phase-locked loop

Memo: Analog multiplier and voltage-controlled circuits

Analog multipliers are commonly available as integrated circuits (IC) and are rarely constructed from scratch due to their complexity. Multipliers commonly have 8 pinouts: X1, X2, Y1, Y2, W, Z, +VCC, -VCC. The common AD632 and MPY634 devices consist of one feedback line (W), two ground lines (X2, Y2), two supply lines (+VCC, -VCC) and one… Continue reading Memo: Analog multiplier and voltage-controlled circuits