I needed to do some AC current measuring with Arduino, more accurately than with special AC current sensor I tested earlier. To do that measuring I bought Meeeno ACS712 Current Measuring Sensor Brick Module Board for Arduino. This is a picture of that module from dx.com:
This module is pretty easy and safe way to measure AC or DC current with Arduino. This module is based on ACS712 current sensor IC. Can measure current value of +/-30A. The output is analog output: 66mV/A. When there is no current flowing, the output is at half of the power supply (powered from 5V source means output is at 2.5V). The module is as such very suitable to be directly connected to Arduino sensor shield three pin analogue sensor connector.
ACS712 sensor IC used on the module is based on hall technology and it provides good isolation from the measured current to Arduino side. Hall technology means that device consists of a precise, low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field which is sensed by the integrated Hall IC and converted into a proportional voltage.The internal resistance of this conductive path is 1.2 mΩ typical, providing low power loss. According to the ACS712 chip data, it provides quite fast operation: 5 µs output rise time in response to step input current and 80 kHz bandwidth (can be reduced with filter pin of needed). The total output error is 1.5% at TA = 25°C
ACS712 provides economical and precise solutions for AC or DC current sensing with 2.1 kVRMS Voltage Isolation. This isolation level allows the ACS712 current sensor IC to be used in applications requiring electrical isolation without the use of opto-isolators or other isolation techniques. This specific module has construction so that there is large insulation distance on the circuit board from measured circuit to output, so that high voltages can be measured safely (some other modules I considered dx.com had input and output sides very near to each other which will most likely not be safe at mains voltages). That 2.1 kVRMS Voltage Isolation and several millimeters distance from measured side to low voltage side means that it could be used for mains current measuring in applications where 2 kV isolation is enough (surge voltages lower than this and no dual-insulation needed). I plan to test this on overcurrent fault protection.
Verdict: Easy to connect to Arduino. Works well. Well constructed module. Reasonable price. If you need current measurement from few amperes to 30A with Arduino, check this sensor module.
5 Comments
Tomi Engdahl says:
You can find several cheap ACS712 based current sensors at
http://www.banggood.com/buy/ACS712.html
Please note than in them there is quite small insulation distance between the measured side and output side, so I would not use many of them them to measure mains voltages.
Tomi Engdahl says:
Here is a nice looking ACS712 based current sensor for 5A current range:
http://www.dx.com/p/acs712-5a-ac-dc-current-sensor-module-for-arduino-blue-black-314493?r=8527370
Tomi Engdahl says:
Current Sensors Magnetic Field Interference Management
http://www.eeweb.com/company-blog/allegro_microsystems/current-sensors-magnetic-field-interference-management/
This article introduces Allegro’s ACS71x current sensor integrated circuits (ICs) without concentrator that can control and minimize external magnetic field interference. These devices can boost performance of small-current differentiation with an easy layout steps.
The ACS71x families of Hall effect-based electrical current sensor ICs measure current by sensing the magnetic field it generates as it passes adjacent to the Hall element (see figure 1). They measure this field directly, without the use of a magnetic concentrator, which is a common feature in other magnetic devices (for example, in the Allegro® MicroSystems CA and CB packages, used for the ACS75x families of current sensor ICs).
The lack of a concentrator has the advantage of nearly eliminating magnetic hysteresis as a source of error in the IC. However, this also leaves the ACS71x devices less shielded from external magnetic fields that could distort the current measurement. In applications where large magnetic fields may be present, care must be taken in the alignment and spacing of the Hall element relative to those fields. Shielding the device may also be desirable in some circumstances.
High-current conductors in the vicinity of the device should be, if possible, oriented perpendicular to the plane on the board on which the device package is mounted
Managing External Magnetic Field Interference When Using ACS71x Current Sensor ICs
http://www.allegromicro.com/en/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-Publications/Managing-External-Magnetic-Field-Interference-ACS71x-Current-Sensor-ICs.aspx?sc_camp=64EB2DD6B3FE4C088C07DB87D5D9B6EF
Tomi Engdahl says:
5 common Hall-effect sensor myths
https://e2e.ti.com/blogs_/b/analogwire/posts/5-common-hall-effect-sensor-myths?HQS=asc-sens-ps-sensors_11myths_2q22-exexnl-ta-ElectronicDesign_0511-wwe_int&DCM=yes&dclid=COuGqYCg2fcCFc5XwgodNK4Iew
Hall-effect sensors are commonly used in automotive and industrial systems for applications including proximity detection, linear displacement measurement and rotary encoding. Currently, the high system performance requirements of modern applications have led to IC manufacturers increasing sensitivity accuracy, integrating more functionality, expanding available sensing directionalities and lowering power consumption in their devices – helping extend the use of Hall-effect sensors for decades to come.
Tomi Engdahl says:
In-Package Hall-Effect Current Sensing: Tackling the Drift Challenge
Jan. 20, 2022
Current sensing is on a trajectory to intersect with the global high-voltage trend of robust, high-performing systems. Discover the tradeoffs between isolated shunt-based, closed-loop Hall-effect, and in-package Hall-effect current sensors.
https://www.electronicdesign.com/technologies/analog/article/21163858/texas-instruments-inpackage-halleffect-current-sensing-tackling-the-drift-challenge?utm_source=EG+ED+Update%3A+Power+and+Analog&utm_medium=email&utm_campaign=CPS220506004&o_eid=7211D2691390C9R&rdx.ident%5Bpull%5D=omeda%7C7211D2691390C9R&oly_enc_id=7211D2691390C9R
What you’ll learn:
Options for high-voltage current sensing.
Historical challenges with in-package Hall-effect current sensors.
In-package Hall-effect current sensor working principles.
For those systems incorporating high-voltage domains, signal and power isolation can help protect people and critical circuits from high-voltage ac or dc power sources and loads. Adding more electrical functionality makes it increasingly important to shrink these systems to make them easier to scale while also reducing bill of materials, simplifying design, and maintaining high performance.
In high-voltage systems, current sensing handles overcurrent protection, monitoring and diagnostics, and closed-loop control. Furthermore, high-voltage systems often require high accuracy for monitoring and controlling loads to maximize efficiency. Power-factor-correction (PFC) circuits, for example, require the accurate sensing of ac currents to improve system efficiency and monitor energy consumption. High-voltage motors require precise in-line motor-current sensing for accurate torque control of the motor.
With so many requirements and variables, it can be difficult to know which current-sensing approach is best for your design. This article explores the tradeoffs and considerations between three different current sensors.
Options for High-Voltage Current Sensing
You have three main options for measuring current in high-voltage applications: isolated shunt-based current sensors, closed-loop Hall-effect current sensors, or in-package Hall-effect current sensors.
Isolated shunt-based and closed-loop Hall-effect current sensors provide the highest levels of accuracy and isolation (Table 1). However, they’re more expensive and larger than in-package Hall-effect current sensors and have more complex designs since they require external components.
Historical Challenges with In-Package Hall-Effect Current Sensors
If size and cost are equally critical to your design, in-package Hall-effect current sensors may be your best option. They can enable high-voltage isolated measurements in a simple, small form factor that requires no external components. However, they’ve historically drifted over time and temperature, which limits their accuracy.
Designers have attempted to reduce this drift and nonlinearity through linear correction efforts, but even these approaches can’t achieve sensitivity below 2%-3% across temperature. Moreover, they only calibrate to temperature at time zero, or a single point in time. To further improve accuracy and lower the sensitivity specification, you could try conducting system-level multipoint calibration to account for temperature drifts. This effort is limited by the testing capabilities, though, plus it adds more cost and takes longer to get a product to market.
The TMCS1100 family of zero-drift in-package Hall-effect current sensors developed by Texas Instruments eliminates this tradeoff.
In-Package Hall-Effect Current-Sensor Working Principles
These zero-drift in-package Hall-effect current sensors enable current flow through the leadframe, which is electrically isolated from the die. The leadframe loop then generates a magnetic field proportional to the current, and a precision Hall-effect sensor converts that magnetic field to a voltage signal
The TMCS1100 provides <1% total error current measurement, and its zero-drift precision signal-chain-architecture improves drift over temperature and eliminates the need for multipoint calibration. In addition, the accuracy helps boost efficiency in systems for better control, while minimizing complexity for any application that needs high-precision isolated current measurements.
Both the TMCS1100 and TMCS1101 provide sufficient lifetime isolation margin and 600 V of working voltage in an 8-pin small-outline IC (SOIC) package with higher lifetime margins than what’s required by industry standard