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Christian Aurich wanted a way to measure current on PCBs without having to cut the traces. He concluded building a probe able to measure current using a Hall Effect sensor. It’s on prototyping phase, so improvements are yet to come. He writes:
In the last weeks I followed an idea to measure current without the need to cut the wires or even open a pcb trace. The solution i came up with is a hall effect based measurement.
I wrote some more about it in an article here: http://avrs-at-leipzig.de/dokuwiki/en/prokekte/fluxprobe
Building a current / flux probe for contactless measurements - [Link]
Here is a PDF document from Linear Technology, featuring current sense circuits for different applications, including High side, low side, level shifting, high and low voltage, fault sensing, etc: [via]
Sensing and/or controlling current flow is a fundamental requirement in many electronics systems, and the techniques to do so are as diverse as the applications them-selves. This Application Note compiles solutions to current sensing problems and organizes the solutions by general application type. These circuits have been culled from a variety of Linear Technology documents.
Current sense circuit collection - [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 application note describes the use of current-sense amplifiers, differential amplifiers, and instrumentation amplifiers to measure battery charge and discharge currents in smartphones, tablets, computer notebooks, and USB accessories. It compares high-side current sense amplifiers with low-side differential amplifiers and recommends selection criteria for current-sense resistors. A high-voltage circuit breaker is described to provide system over-current protection due to faults and short circuits. Application circuits for a variable linear current source and a programmable 0–5A current source are included.
High-Side Current-Sense Measurement: Circuits and Principles - [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]
Jon Gabay writes:
Current measurement and control are an integral part of any power sensitive system. While most of us have used ammeters to measure current, it is unlikely that budget, space and other practical constraints will allow design engineers to specify an ammeter as part of a finished product; more likely, we will embed some current measurement technique within a given design.
Current measurement has a wide range of uses. Some of these are:
- Making sure a power supply is not damaged by receiving too much current.
- To estimate the rotational speed of a motor (the speed of a motor is directly proportional to the amount of current applied to it).
- To check whether an LED has correct illumination.
- To determine how much current is being applied to a battery pack during charging (so as to prevent overcharging or overheating the batteries).
- To measure the amount of current being applied to a circuit from the battery pack, enabling estimation of the battery life.
Active Current Measurement Saves Power, Enhances Safety - [Link]
20 Amps DC Ammeter using very low value resistance of 0.01 Ω
- Supply voltage. symmetric power (+ -12)
- Maximum current measure. 20A
- With Possibility of increasing the measurement range
- Resolution 10mA
20 Amps DC Ammeter - [Link]
Learn how to implement fixed current limiting in power-supply designs: [via]
In every power supply application there exists the possibility to short the output to ground causing excessive current to be drawn from the power supply. In order to limit the output current from becoming excessive the following examples of current limiting circuits are suggested.
App note: External current limiting circuit - [Link]
With current transformers, you can measure AC current simply and with a sufficient accuracy, moreover with maintaining of a high safety level thanks to a galvanic isolation.
General purpose AC current measurment, overload and shortcut protection, load drop or shutdown detection and similar application require simple and reliable solution. Current transformers meet all these requirements and they add further bonuses like galvanic isolation, no intervention to a measured circuit and a convenient price.
As we know, one of AC current measurement methods is based on the usage of a current transformer. Alternating magnetic field around a wire lead, which in a continual proportion to a current flowing through a wire, will induce an AC voltage in a measurement transformer. At a suitable construction and a right transformer loading, is the output voltage in a continual proportion to a current in a measured lead. Perhaps the biggest advantage of this method is the fact, that a measuring circuit is galvanically isolated from a measured lead and at the same time, the transformer doesn´t indtroduce any added load neither any influence. If we´d like to go to a detail, the transformer consumes a negligible amount of energy of few tens of mW/10A from a measured lead, which is being lost in the winding and a load of the transformer.
Every current transformer is designed for a certain load, i.e. at a certain load it provides most accurate results. For example for the type AC-1050 it is 100 Ohms. In such a case is valid a transfer ration 1000:1, i.e. to the load flows a 10 mA current at a 10A current in a measured lead. It means, that on a 100 Ohm we will measure a voltage with a value of 1V. Output of a current transformer can be connected to a panel meter, digital voltmeter, oscilloscope or an AD converter input. By using an AD converter, it is also possible to monitor a course of a current and to discover various nonlinearities in a power consumption.
Talema current transformers are top quality components with an outstanding quality / price ratio. Transformers are designed for soldering into a PCB. In our offer you can find more types, up to 100A maximum current. Currently we can offer you type AC 1050 also from the producer´s stock (ca. 8000 pcs) with 1-2 weeks delivery time (standard delivery time uses to be 20 weeks). Detailed information will provide you datasheets at given types.
Precise and price-convenient measuring of AC current - [Link]
David L. Jones writes:
A current adapter for multimeters?
“But don’t most multimeters already have current measurement ranges?” I hear you ask. Well, yes, they do of course. But most multimeters, be they a no-name $10 hardware store throwaway model, or a $1000 highly accurate brand name meter, all suffer from two rather annoying issues with their current measurement ranges – burden voltage and reduced accuracy.
Burden Voltage
The biggest problem with current measurement ranges is called “burden voltage”. This is the voltage that the internal current shunt resistor drops as you pass your circuit current through it. The burden voltage is typically specified in millivolts per Amps (mV/A). The value will change for different current ranges, so you might have 1mV/A, 1mV/mA, or 1mV/μA for example.
Normally you may not give burden voltage a second thought, as like many, you probably think it’s fairly insignificant in most applications. In fact, most people would be hard pressed to tell you what the burden voltage of their particular multimeter actually is. It’s usually buried away in the user manual, if it’s mentioned at all. Next time you borrow a colleague’s meter, ask them what the burden voltage is, and watch their reaction…
µCurrent – A Professional Precision Current Adapter for Multieters - [Link]
