DETAILED DESCRIPTION
Project Idea
This device is intended for measuring current consumed by an USB device. Measuring the DC current is easy achievable by using a multimeter. However, for debugging purpose it is often more interesting to see how the current consumption changes. Especially in low power application it is necessary to check, whether the microcontroller is in sleep mode or not. So, the USB Current Probe is an addition to the multimeter and can be hooked up to an oscilloscope.
This device will be used for debugging purposes. If you are interested in a more precise measurement device, please refer to David Jones µCurrent.
A current sense IC (MAX9923H) is used for the current measurement. The differential voltage of the shunt is amplified by 100V/V.
Specification
Power supply (for the measurement circuit): coin cell (CR2032)
Input: micro USB or 4mm sockets (for DUT supply)
Output: USB type A for DUT supply, USB supply voltage (SMA connector), USB supply current (SMA connector)
Range | Rsense | Measurement Error* | Effective Range |
---|---|---|---|
1V/A | 10mΩ ±1% | approx. 1.4% | 1mA ... 2A |
1kV/A (1V/mA) | 10Ω ±0.1% | approx. 0.5% | 1µA ... 2mA |
*The measurement errors where calculated using the error of Rsense and the gain accuracy of the MAX9923H at 25°C.
Current Project State
I've assembled a PCB. Reference measurement haven't been done yet.
Unimportant resistors and capacitors are not linked to octopart. As well as some parts that I purchased from Aliexpress. A complete BOM with all part numbers and hyperlinks can be found in the attachments.
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