SUF shared his voltage reference project in the forum:
To achieve the things above I designed a small battery good indicator circuit with a zener an opamp two LEDs and a few resistors. If you switch it on and the battery fall below 8V the red LED will lit instead of the green. I wanted to have a SOB style case. I designed a new one with a trick on it. I used a third acrylic plate what has a hole inside. The hole can accommodate the battery and the battery clip. This setup keeps the battery in place.
Voltage reference project - [Link]
A team of Columbia Engineering researchers, led by Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard, exploring the properties of graphene have demonstrated a new electro-mechanical resonant component.
The resonator’s structure consists of a 2-4 micrometer long strip of graphene suspended over a metal gate electrode. The strip of graphene has a natural resonance governed by its physical dimension and is used in the demonstration as the frequency determining element in an RF feedback oscillator circuit. Applying a voltage to the gate electrode stresses and deflects the graphene strip changing its resonant frequency. The team applied baseband audio and tones to the gate electrode to produce a 100 MHz FM signal.[via]
Tiny FM Transmitter uses Voltage Controlled Graphene Resonator - [Link]
startingelectronics.com has a very clear tutotrial on how to read analog voltages using Arduino:
Analog channels A2 to A5 on an Arduino Uno are used to measure four different voltages. The measured voltages are displayed on a 16 character by 2 line LCD. The four channel Arduino multimeter can measure four independent DC voltages that can each be in the range of 0 to 50V. Voltages are displayed with one decimal place, e.g. 5.3V, 12.8V, etc.
Arduino LCD Voltmeter with 4 Channels - [Link]
Have you ever wanted to take a standard voltage op-amp and turn it into a high voltage output circuit? Here is a technique that requires some shunt regulators to power the chip and some current limiting transistor circuitry for the output. This example should work upto +/- 120V.
Make an Op-Amp High-Voltage Output Circuit - [Link]
Kerry Wong shows how to make an adapter circuit for measuring very low voltages with a multimeter.
A typical 3 ½ or 4 ½ multimeter can measure voltage in the low mV range and current in the low mA range. Voltage measurement in the µV range and current measurement in the nA range are typically only available in the more expensive lab bench multimeters. In this post, I will show you a simple adapter circuit that can be used for precision voltage measurement down to the µV range. Using this circuit along with the current adapter circuit I discussed earlier you will be able to perform most of the low level measurements with a 3 ½ meter.
Precision Voltage Adapter For Low Voltage Measurement - [Link]
The INA230 is a current-shunt and power monitor with an I2C interface that features 16 programmable addresses. The INA230 monitors both shunt voltage drops and bus supply voltage. Programmable calibration value, conversion times, and averaging, combined with an internal multiplier, enable direct readouts of current in amperes and power in watts.
INA230 – Precision digital/current/voltage/power monitor - [Link]
When specifying a reference, keep in mind that initial accuracy, temperature coefficient and long-term stability all play a role in overall accuracy of the finished product. By taking some care in applying the reference, and by avoiding some key pitfalls, the reference’s inherent accuracy can be preserved.
Using and understanding voltage references - [Link]
INA219 is a cool IC that measures voltage and current trough a shunt resistor, and relays the information over I2C. It provides the multiple of the two values, thus enabling easy power measurement. Opossum used it along with a Nokia 5110 LCD and a MSP430 LaunchPad to build a nice power-meter.
Measuring power with INA219 and an MSP430 Launchpad - [Link]
Over the years most of us have purchased a few multimeters, and perhaps some of the older ones are still hanging around like faithful friends. You might prefer one ahead of the others, perhaps because it is easier to use and you think that it is probably more accurate, but you wonder just how accurate it is…
Determining the accuracy of a DMM is not easy. Often manufacturers will totally ignore accuracy in their specifications, or if it is a high quality model, they might say something like ±0.02% ±3 digits ±4mV/°C — which does not help either.
This gadget will output a precise 2.500V with an accuracy of ±1 mV. It is great for checking any meter, it does not cost much, and it must be one of the simplest projects around.
MAX6325 Precision Voltage Reference - [Link]
The TL431 is a three-terminal adjustable shunt regulators, with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors.
- Operation from -40°C to 125°C
- Reference voltage tolerance at 25°C
- 1%: A grade
- 2%: standard grade
- Low output noise
- 0.2-Ω typical output impedance
- Sink-current capability: 1 mA to 100 mA
- Adjustable output voltage: Vref to 36 V
TL431: Cost-effective shunt regulator solution - [Link]