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ABernard
Using an electrocardiogram (ECG sometimes called an EKG) is an invaluable way to identify various physical ailments. Today there is a wide array of cardiac equipment that displays and interprets ECG signal patterns. Medical equipment designers need a flexible way to seamlessly generate accurate ECG signal patterns to verify and test their designs.… (Show more)
ABernard
Single-ended signals are referenced to a common level, such as ground, that they can share with other signals, so a single-ended signal requires only a single path or wire. Differential signals are made up of a pair of paths that are both dedicated to a single signal at any given time. One path is used at a higher potential than the other.… (Show more)
ABernard
True RMS responding DMMs measure the "heating" potential of an applied voltage. Power dissipated in a resistor is proportional to the square of an applied voltage, independent of the wave shape of the signal. Today’s general purpose DMMs can accurately measures true RMS voltage or current, as long as the wave shape contains negligible energy… (Show more)
ABernard
The digital multimeter or DMM offers two methods for measuring resistance: 2–wire and 4–wire ohms. For both methods, the test current flows from the input HI terminal and then through the resistor being measured. For 2–wire ohms, the voltage drop across the resistor being measured is sensed internal to the multimeter. Therefore, test lead… (Show more)
StevenLee
Today I want to talk about what causes an overvoltage condition. I’m defining an overvoltage condition as a condition that causes the power supply output voltage to exceed its setting. Let’s take a look at some of the things that can cause this to happen.Causes of power supply output voltage exceeding its setting User-caused miswiresThese miswires… (Show more)
StevenLee
Occasionally, one of our power supply users contacts us with a question about voltages measured from one of the power supply output terminals to earth ground (same as chassis ground). All of our power supply outputs are floating with respect to earth ground. See my previous post about this here. In that post, I stated that neither output terminal… (Show more)
StevenLee
Previously I posted about hurricane Irene and inverters. In that post (click here to read), I talked about the power ratings for inverters and just skimmed the surface about the differences between ratings in watts (W) and volt-amperes (VA). In this post, I want to go further into detail about these differences. Both watts and VA are units of… (Show more)
ABernard
A true ground potential is something that only exists on paper or in simulations. In the real world there is no such thing as a true ground which in test and measurement leads to ground loop errors. Ground loops present problems when measuring low level signals such as thermocouple measurements. When measuring voltages in circuits where the DMM… (Show more)
StevenLee
On a previous posting “The difference between constant current and current limit in DC power supplies”, I discussed what differentiates a DC power supply having a constant current operation in comparison to having strictly a current limit for over-current protection. In that post I had depicted one very conventional current limit behavior. However… (Show more)
ABernard
This is part 2 of a 2-part post that takes a comprehensive look at all of the factors that can lead to errors in a DC voltage measurement with a DMM and how to eliminate them so you can achieve the highest accuracy possible in your measurement. In part 2 we will cover the following topics: loading errors, power-line noise and injected current… (Show more)
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