Measurements of electric current are an indispensable functionality of laboratory instruments and universal meters intended for field use. It is worth remembering, however, that such measurements are also necessary in many other devices, e.g. electric motor controllers - determination of an accurate value of a momentary current consumption is of utmost importance to ensure safety of the whole system, since a sudden increase in current supply to the motor (or other executive element) usually means its overload or even failure (e.g. short circuit in an output circuit). In this category we present current sensors offered by the manufacturer of a series of Gravity modules - DFRobot.
The magnetic field sensor with digital output OH9249. It is supplied with the voltage of from 3.3 V to 5 V, it works with Arduino modules.
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Electronic engineers today have many methods for measuring current values - both direct current (DC) and alternating current (AC). While some methods can be applied to both types of current, some techniques are suitable only for one of them. The classic and oldest group of methods for determining the value of alternating currents are techniques based on the phenomenon of electromagnetic induction. Popular current transformers, which are a kind of simple transformers, operate on this principle. Current transformers are used to measure currents of particularly high currents (of the order of tens of amperes and more), although there are also versions available for precise measurements of small currents (below 10 A). For example, the AC current sensor SCT 013-020 allows for measurement of currents up to 20 A, and the construction of the transformer allows for its installation on a wire without cutting the circuit - the measuring probe has the form of a convenient clip in a solid plastic insulation.
Hall effect sensors
Another group of sensors, often used in various industries, is based on the Hall effect. The flow of current in the measured circuit generates a magnetic field whose intensity (and thus also induction) changes proportionally to the instantaneous value of the current. Thanks to this, Hall effect sensors can be used to measure both alternating and direct currents - it is worth remembering that the latter cannot be measured using the previously described transformers. Although the design of Hall effect current sensors is quite demanding in terms of technology, fortunately, the modern electronics engineer does not have to go through the trouble of building such a measuring unit from scratch - there are a number of high quality integrated sensors on the market, ready to be used in any electronic circuit. These sensors offer outputs in analog (voltage) or digital form, which significantly facilitates implementation in the target device. An example of this type of sensor is the module with catalog number DFR-08367, powered by 5 V (on the analog interface) and capable of measuring DC and AC currents up to 20 A.
Other interesting measurement modules from the Gravity series
DFRobot also offers other modules, perfect for use in various devices and installations for teaching and scientific purposes. An example of such a solution is the integrated module for the measurement of energy consumption in systems supplied with constant voltage (DC) in the range up to 26 V and with current consumption not exceeding 8 A. The small board with index DFR-13753 is equipped with a 4-pin Gravity connector and communicates with an external microcontroller via an I2C serial interface. It can measure energy with an accuracy of 0.2% and is compatible with Arduino and Raspberry Pi, among others. In many practical applications, the 3.7V Li Battery Fuel Gauge V1.0 module can also be used, providing the function of measuring the charge level of a 1-cell lithium-polymer battery. The chip has reverse polarity protection and also offers an alarm output in the form of two goldpin solder pads.