4-wire mode

In 4-wire mode, also known as Kelvin connection, the voltage measurement (sensing) is separated from the power. The reason for separating the cables is that in the cables that also powers the Device Under Test (DUT) there will be a voltage drop, due to the cable resistance and the current. In the sensing cables, there is no, or very low, current, so there is very low voltage drop. When 4-wire is enabled, there will be 4W symbol highlighted next to the voltage measurement, to show that the voltage is measured from the SENSE pins.

In 4-wire mode, the regulated voltage will not be changed, only the measured voltage.

There are requirements on the SENSE pin measurement to have 4-wire active and they differ from Otii Arc Pro and Otii Ace Pro. For Arc, (SENSE+) must be withing 400mV from (Main+) and (SENSE-) must be within 400mV from (Main-), that also is GND. For Ace, (SENSE+) - (SENSE-) must be within 500mV from (Main+) - (Main-)

Otii hardware setup

  1. Connect Otii hardware to your computer via USB. If needed, add a DC power supply via the DC plug.
  2. Connect Otii hardware’s banana connector positive lead to DUT positive (+) battery connector/power connector.
  3. Connect Otii hardware’s banana connector negative lead to DUT negative (-) battery connector/power connector (GND).
  4. Connect Otii hardware’s SENSE+ pin to DUT positive (+) battery connector/power connector.
  5. Connect Otii hardware’s SENSE- pin to DUT negative (-) battery connector/power connector (GND).
  6. Connect Otii hardware’s AGND pin to DUT 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. Considering the DUT's power ranges, set the required voltage for the added Otii hardware in the voltage box located on the left side of the power supply button.
  4. Under General Settings, make sure:
  • Power Box option is selected.
  • 4-wire is selected.
  1. Under Channels, select Main current and Main voltage to measure the current and voltage.
  2. [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)
  3. 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.
  4. Under the CONTROL section, turn on the DUT by clicking the power button. Once turned on, the DUT measurements are being recorded.
  5. Now it's time to validate, analyze, and optimize your embedded system or IoT devices. The Main Voltage measurement is now from the SENSE pins, instead of the banana connectors.