Electronics-Lab.com Blog

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.

Resources: Datasheet

INA230 – Precision digital/current/voltage/power monitor - [Link]

This tutorial on voltage references covers theory and how it works in practice – [via]

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]

dangerousprototypes.com writes:

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]

geoffg.ne writes:

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.

Features:

• 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]

The TS1001 from Touchstone Semiconductor is a single-supply, rail-to-rail operational amplifier with the unique ability to operate from a 0.8 V supply voltage with a supply current of 600 nA, reducing overall power consumption by at least 50% compared to other low-voltage operational amplifiers.

Optimised for ultra long life battery-powered applications, the TS1001 is Touchstone’s first operational amplifier in the NanoWatt Analog™ high-performance analogue integrated circuits family. The TS1001 has a typical offset voltage of 0.5 mV, a typical input bias current of 25 pA, and rail-to-rail input and output stages. The TS1001 can operate from single-supply voltages from 0.65 V to 2.5 V. [via]

Low-voltage opamp runs on 0.8 V supply voltage - [Link]

RC time constant / voltage calculator.

Intrepid adafruit engineer Kevin Townsend came up with this very handy javascript calculator for figuring out exactly how long it takes for an RC delay to reach a certain voltage. Handy for when you want to make a delay (by charging up a capacitor) or when you want to avoid a delay (by calculating how much delay is caused by your fet/transmission line capacitance) Take it for a spin today!

RC time constant / voltage calculator – [Link]

Keithley Instruments, Inc has published an electronic handbook titled “Making Precision Low Voltage and Low Resistance Measurements”. The handbook, which offers instant online access to a wide range of Keithley application notes, white papers, webinars, and many other references, was developed to help readers solve today’s toughest low level measurement challenges. It can be downloaded at no charge from the url below. [via]

A number of topics related to low voltage measurements are addressed in the handbook:

• Offset voltages
• Noise
• Common-mode current and reversal errors
• Low resistance measurement topics covered include:
• Lead resistance and the four-wire method
• Thermoelectric EMFs and offset compensation methods
• Non-ohmic contacts
• Device heating
• Dry circuit testing
• Testing inductive devices

Free E-Handbook on low voltage, low resistance measurements - [Link]