External power source

Measures system's current and voltage while it is energized by an external power source.

Otii hardware's external power source setup

If the Device Under Test (DUT) needs to be powered from an external source while still measuring system current and voltage, an external shunt resistor connected to the ADC inputs of the Otii hardware, whether the Otii Arc Pro or Otii Ace Pro, can manage this.

Products required

Hardware

• Otii hardware: Otii Arc Pro, or Otii Ace Pro

• DUT

• Shunt resistor – How to choose the resistor?

• Jumper wires

Software

• Otii 3 Desktop App

Otii hardware setup

1. Connect Otii hardware to your computer via USB. If needed, add a power supply via a DC power adaptor.

2. Connect the external shunt resistor in series between the external power supply's positive (+) line and DUT's positive (+) battery connector.

3. Connect ADC+ and ADC- across the resistor to measure the voltage over the resistor.

4. Connect Otii hardware's AGND to the DUT's GND.

Otii software setup

1. Open the Otii 3 Desktop App, then select "Create a new Otii Project."

2. In the left sidebar, find the CONTROL section. Within this section, add the Otii hardware identified by your computer. Just click the add button on the right side of the hardware identified.

3. Under "General Settings," make sure:

   • "Power Box" option is selected.

   • Set the value of the shunt resistor in the "ADC resistor" field. Check how to choose the resistor if you are not sure how to do it.

4. Under "Channels," select "ADC current" to measure the current over a shunt resistor. In the case of measuring voltage over the shunt resistor, the "ADC voltage" must be selected as well.

5. [Optional] The previously selected channels will be listed under the MEASUREMENTS section. In this section, the sampling rate, up to 50 ksps, can be set. (Only possible with the Otii Ace Pro)

6. Click the record button in the upper left corner of the toolbar to start recording DUT measurements. Since your DUT is not powered on yet, only noise measurements will be observed at first.

7. Under the CONTROL section, turn on the DUT by clicking the power button. Once turned on, the DTU measurements are being recorded.

8. Now it's time to validate, analyze, and optimize your embedded system or IoT devices.

Keep in mind

🔋 The voltage over the shunt resistor is measured differentially. No extra signal ground is needed if you only want to measure the current.

🔋 If voltage measurement is required, it is measured between ADC+ and AGND. In this case, AGND needs to be connected to the ground of the DUT.

The maximum voltage range on ADC pins are:

• 0V to 5 V for Otii Arc Pro

• -10V to 25V for Otii Ace Pro