Wireless current sensing with a micropower zero-drift Op Amp: Page 4 of 4

June 13, 2018 // By Kris Lokere
Many current sense circuits follow the same simple recipe: develop a voltage drop across a sense resistor: amplify the voltage, read it with an ADC, and now you know the current. But if the sense resistor is at a voltage that is very different from system ground, things can quickly get complicated.

Combining Linear Technology and Analog Devices signal chain, power management, and wireless networking products enables the design of a truly wireless current sense circuit. Figure 3 shows an example implementation. The new ultralow power LTC2063 chopper op amp can accurately read small voltage drops across a sense resistor. The entire circuit, including micropower ADC and voltage reference, floats with the common mode of the sense resistor. The nanopower LTC3335 switcher can power the circuit for years from a small battery, while reporting cumulative battery usage with its built-in Coulomb counter. The LTP5901-IPM wireless module manages the entire application and automatically connects to a highly reliable SmartMesh IP network.


Fig. 3:  A complete wireless current sense circuit is implemented on a small circuit board. The only physical connections are the banana jacks for the current to be measured. The wireless radio module is shown on the right. The circuit is powered from two AAA batteries connected on the back of the board.

 

About the author:

Kris Lokere is Strategic Applications Manager, Signal Conditioning Products at Analog Devices – www.analog.com

Design category: 

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