Power source and measure a Device Under Test (DUT)
Set up Otii hardware, either the Otii Arc Pro or Otii Ace Pro, to work as a power source box providing constant voltage to the DUT, ranging from 0.5V-5V / 0V-25V, and enable it to measure output current and voltage.
Connect Otii hardware to your computer via USB. If needed, add a DC power supply via the DC plug.
Connect Otii hardware’s banana connector positive lead to DUT positive (+) battery connector/power connector.
Connect Otii hardware’s banana connector negative lead to DUT negative (-) battery connector/power connector (GND).
In case of connecting the DUT using the battery connector, remove the battery prior to connecting it to the Otii hardware.
Open the Otii 3 Desktop App, then select "Create a new Otii Project."
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.
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.
Under "General Settings," make sure that the "Power Box" option is selected, and set an OC (overcurrent) protection for the DUT.
Under "Channels", select "Main current" to measure DUT's output current and "Main voltage" to measure DUT's output voltage. The "Main power" channel is assigned by default when the main current is selected to measure DUT's energy consumption.
[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)
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.
Turn on the DUT by clicking the power button next to the desired voltage assigned. Once turned on, the DTU measurements are being recorded.
Now, it's time to validate, analyze, and optimize your embedded system or IoT devices.
🔋 Use wires with the lowest possible resistance and keep them as short as possible to minimize voltage drop, especially when the DUT consumes high current. The resistance in wires will be added to the total series resistance within the system, causing an unwanted voltage drop and an error in power and energy consumption measurements.
🔋 If the DUT consumes high current during power-up, causing high voltage drops in the attached wires, which directly affects the power-up cycle of the DUT since the voltage is too low. In case of experiencing this, connect one or several capacitors from Bat+ to Bat- on the DUT side to stabilize the voltage to start up the DUT properly. Note that the Otii Arc and Otii Ace have very low output capacitance for being a power source for the DUT but also a programmable load.
Capture and record Device Under Test (DUT) serial logs
Set up Otii hardware, Otii Arc Pro, or Otii Ace Pro to capture logs from the DUT serial log.
Connect Otii hardware to your computer via USB. If needed, add a DC power supply via the DC plug.
Connect Otii hardware’s banana connector positive lead to DUT positive (+) battery connector/power connector.
Connect Otii hardware’s banana connector negative lead to DUT negative (-) battery connector/power connector (GND).
Connect Otii hardware's RX pin to the DUT TX pin.
Connect Otii hardware's DGND to the DUT GND pin.
In case of connecting the DUT using the battery connector, remove the battery prior to connecting it to the Otii hardware.
Open the Otii 3 Desktop App, then select "Create a new Otii Project."
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.
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.
Under "General Settings," make sure:
"Power Box" option is selected.
Set digital voltage according to the DUT's digital voltage level for the UART
Set an OC (overcurrent) protection for the DUT.
Under "Channels," choose the measurements desired to be recorded (e.g., main current, main voltage, main power, among others)
Under "UART", make sure:
Assign the DUT's baud rate.
Select "UART log" to enable the serial communication. Once enabled, the console log will automatically open.
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.
Under the CONTROL section, turn on the DUT by clicking on the power button located right next to the desired voltage assigned. Once turned on, the DTU measurements are being recorded.
Now it's time to validate, analyze, and optimize your embedded system or IoT devices.
Explore hardware setup examples for a variety of use cases.
Otii hardware features two main connectors and one expansion port. Multiple channels can be measured with the available inputs, such as main current, main power, main voltage, ADC current, ADC voltage, SENSE+ voltage, SENSE- voltage, GPI1, and GPI2, as well as capturing serial logs from any embedded system or IoT devices.
To get the most out of the Otii Arc Pro and Otii Ace Pro, start by checking out the to explore how to enhance measurement capabilities.
Discover hardware setup examples for a variety of use cases:
When using an external DC adapter, choosing one from an established supplier is highly recommended. The adapter should be low-noise, comply with IEC 60950-1 as a Limited Power Source, and have an output of 7 to 9 VDC for the Otii Arc Pro and 7 to 20 VDC for the Otii Ace Pro, with a maximum of 5A.
Visit the for more information on selecting the proper power supply.
AGND is utilized as a reference point for analog measurements.
DGND is used as a reference point for digital signaling.
Measures system's current and voltage while it is energized by an external power source.
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.
Connect the external shunt resistor in series between the external power supply's positive (+) line and DUT's positive (+) battery connector.
Connect ADC+ and ADC- across the resistor to measure the voltage over the resistor.
Connect Otii hardware's AGND to the DUT's GND.
Open the Otii 3 Desktop App, then select "Create a new Otii Project."
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.
Under "General Settings," make sure:
"Power Box" option is selected.
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.
[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)
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.
Under the CONTROL section, turn on the DUT by clicking the power button. Once turned on, the DTU measurements are being recorded.
Now it's time to validate, analyze, and optimize your embedded system or IoT devices.
🔋 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.
0V to 5 V for Otii Arc Pro
-10V to 25V for Otii Ace Pro
A separate ground wire for the signal ground, attached to either DGND (Digital Ground) or AGND (Analog Ground) on the , should be used. This will prevent disturbances and measurement errors caused by voltage drops in the negative battery wire.
Connect Otii hardware to your computer via USB. If needed, .
Set the value of the shunt resistor in the "ADC resistor" field. Check if you are not sure how to do it.
The are:
Hardware
Otii hardware: Otii Arc Pro, or Otii Ace Pro
DUT
Banana connectors cables
Software
Hardware
Otii hardware: Otii Arc Pro, or Otii Ace Pro.
DUT
Banana connectors cables + jumper wires
Software
Hardware
DUT
Jumper wires
Software
Expand Otii hardware capabilities: additional measurements or trigger external events
The expansion port on the front of the Otii hardware is designed to enhance the hardware functionality, allowing users to measure additional voltages and currents or trigger external events. These enable complex testing setups, allowing users to expand measurement capabilities beyond standard power analysis, offering flexibility across diverse use cases from development to debugging.
Fourteen additional pins are available on the expansion port, which features multi-input and multi-output for analog and digital signals, serial communication, and additional power and ground points. Depending on the project requirements, these pins can be easily enabled and set up as needed within the Otii 3 Desktop App.
Note that the expansion port is designed to be identical across the Otii hardware versions, but capabilities in terms of voltage range, impedance and resolution differ from one version to the other.
The Otii Arc Pro features the following extension port:
| Pin | Description |
|---|---|
The serial ports known as RX (received data) and TX (transmitted data) enable serial communication between the Otii hardware and the Device Under Test (DUT) to provide real-time logs of how the code is impacting the battery draining. Moreover, these ports can be designated as GPIOs at the software level through the scripting feature using Otii Toolbox.
The digital I/O (GPIO) ports consist of six ports in total: two input ports and two output ports on the hardware level, plus additional input and output ports that can be set up on a software level by scripting.
These ports manage a voltage range from 1.2V to 5V, which can be set within the Otii 3 Desktop App. Check out the corresponding documentation to set up the ports according to your system's needs.
The chosen voltage level will be applied to all six (6) available digital I/O ports.
The analog ports consist of four analog inputs subdivided into two groups:
SENSE ports are general-purpose analog-to-digital inputs.
ADC ports are used to measure current over a shunt resistor.
General purpose analog to digital inputs enable voltage measurement using the AGND port as a reference. In addition, 4-wire measurements can be used to compensate for the voltage drop in the power supply leads.
Using the scripting feature—available with Otii Toolbox—one signal minus the other can be configured to measure differential voltages.
These ports manage a voltage input range of 0V to 5V with a 12-bit resolution and an input impedance >1 Mohm.
These ports are dedicated to measuring the current over a shunt resistor or the voltage from one node of the resistor with the AGND port as a reference; note that the voltage over the resistor is measured differentially. The ADC ports can manage either positive or negative currents.
These ports manage a single-ended voltage input range of 0V to 5V and a differential voltage range of -81.9175 mV to 81.2 mV, managing both voltage and current with 16-bit resolution.
The use case "Measuring a subsystem" is highly suggested to understand how to measure current over a shunt resistor, as well as the guidelines on how to choose the proper resistor.
The Otii Arc Pro provides three ground (GND) ports: one analog ground (AGND) port dedicated to analog measurements and two digital ground (DGND) ports dedicated to digital signals.
In addition, it has an additional 5V (max 500 mA) output voltage port that can be switched on and off as required via the Otii 3 Desktop App under the "CONTROL" section once the Otii Arc Pro is successfully connected. It can also be switched by the scripting feature using the Otii Toolbox.
Powering the Otii Arc Pro with a DC adapter is highly recommended if this pin is used for 5V output voltage.
Do not exceed the minimum or maximum voltages on any port. This may cause damage to the Otii hardware.
The Otii Ace Pro features the following extension port:
The serial ports known as RX (received data) and TX (transmitted data) enable serial communication between the Otii hardware and the Device Under Test (DUT) to provide real-time logs of how the code is impacting the battery draining. Moreover, these ports can be designated as GPIOs at the software level through the scripting feature using Otii Toolbox.
The digital I/O (GPIO) ports consist of six ports in total: two input ports and two output ports on the hardware level, plus additional input and output ports that can be set up on a software level by scripting.
These ports manage a voltage range from 1.2V to 5V, which can be set within the Otii 3 Desktop App. Check out the corresponding documentation to set up the ports according to your system's needs.
The chosen voltage level will be applied to all six (6) available digital I/O ports.
The analog ports consist of four analog inputs subdivided into two groups:
SENSE ports are general-purpose analog-to-digital inputs.
ADC ports are used to measure current over a shunt resistor.
General purpose analog to digital inputs enable voltage measurement using the AGND port as a reference. In addition, 4-wire measurements can be used to compensate for the voltage drop in the power supply leads.
Using the scripting feature—available with Otii Toolbox—one signal minus the other can be configured to measure differential voltages.
These ports manage a voltage input range of -10V to 25V with a 24-bit resolution and an input impedance >100 Mohm.
These ports are dedicated to measuring the current over a shunt resistor or the voltage from one node of the resistor with the AGND port as a reference; note that the voltage over the resistor is measured differentially. The ADC ports can manage either positive or negative currents.
These ports manage a single-ended voltage input range of -10V to 35V and a differential voltage range of -102.4mV to 102.4mV, managing both voltage and current with 24-bit resolution.
The use case "Measuring a subsystem" is highly suggested to understand how to measure current over a shunt resistor, as well as the guidelines on how to choose the proper resistor.
The Otii Ace Pro provides three ground (GND) ports: one analog ground (AGND) port dedicated to analog measurements and two digital ground (DGND) ports dedicated to digital signals.
In addition, it has an additional voltage output ranging from 0V to 15V (max 600mA), which can be switched ON or OFF, as needed, from the Otii 3 Desktop App under the "CONTROL" section once the Otii Ace Pro is successfully connected. It can also be switched by the scripting feature using the Otii Toolbox.
Powering the Otii Ace Pro with a DC adapter is highly recommended if this pin is used for 0-15V output voltage.
Do not exceed the minimum or maximum voltages on any port. This may cause damage to the Otii hardware.
Power source and measures subsystem's current and voltage
Set up Otii hardware, Otii Arc Pro, or Otii Ace Pro to measure a subsystem current and voltage over a shunt resistor in addition to measuring the complete system. Note that the resistor can be part of the actual system or applied externally.
Connect Otii hardware to your computer via USB. If needed, add a DC power supply via the DC plug.
Connect Otii hardware’s banana connector positive lead to DUT positive (+) battery connector/power connector.
Connect Otii hardware’s banana connector negative lead to DUT negative (-) battery connector/power connector (GND).
Connect Otii hardware's ADC+ and ADC- across the shunt resistor for current measurement; no additional ground is needed for this. Make sure to connect the shunt resistor side with the high side to ADC+ and the one with the low side to ADC-. Note that if negative currents are measured, the high side has a lower potential than the low side.
[Optional] To measure voltage, connect AGND to the DUT's ground and measure the voltage between ADC+ and AGND.
In case of connecting the DUT using the battery connector, remove the battery prior to connecting it to the Otii hardware.
Open the Otii 3 Desktop App, then select "Create a new Otii Project."
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.
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.
Under "General Settings," make sure:
"Power Box" option is selected.
Set an OC (overcurrent) protection for the DUT.
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.
Under "Channels," select "ADC current" to measure the subsystem current over a shunt resistor. In the case of measuring voltage, the "ADC voltage" must be selected as well. If the system itself needs to be measured, it can also be measured; select the channels desired to be measured in addition to the ones previously selected.
[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)
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.
Under the CONTROL section, turn on the DUT by clicking on the power button located right next to the desired voltage assigned. Once turned on, the DTU measurements are being recorded.
Now it's time to validate, analyze, and optimize your embedded system or IoT devices.
🔋 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
The differential input voltage range for the Otii Arc Pro ADC inputs goes from -81.9175 mV to 81.92 mV. Based on these values, the absolute maximum (peak) current through the sensing resistor must be determined.
Remember that by using Ohm's Law (V = I x R | I = V / R | R = V / I), the relationship between voltage, current, and resistance in an electrical circuit can be determined.
Here's an example to illustrate how to choose the resistor:
Suppose the system has a maximum peak current of 200 mA. By calculating, 0.08192 V / 0.2 A, the resistor value is equal to 0.41 ohms. But, the closest standard resistor value is 0.39 ohms. Resulting in a measuring range of 0.08192 V / 0.39 ohms = 0.210 A.
In conclusion, a 0.39 ohm sensing resistor will result in a measurement range of +/- 0.210 A.
Following the same example as above, let's do the same for now but for the Otii Ace Pro.
The differential input voltage range for the Otii Ace Pro ADC inputs goes from -102.4 mV to 102.4 mV. Based on these values, the absolute maximum (peak) current through the sensing resistor must be determined. Here's an example to illustrate how to choose the resistor:
Suppose the system has a maximum peak current of 200 mA. By calculating, 0.1024 V / 0.2 A, the resistor value is equal to 0.512 ohms. But, the closest standard resistor value is 0.51 ohms. Resulting in a measuring range of 0.1024 V / 0.51 ohms = 0.200 A.
In conclusion, a 0.51 ohm sensing resistor will result in a measurement range of +/- 0.200 A.
Otii hardware: , or
Shunt resistor –
| UART | Min | Typical | Max |
|---|---|---|---|
| DIGITAL I/O | Min | Typical | Max |
|---|---|---|---|
| Differential ADC, pins ADC- and ADC+ | Min | Typical | Max |
|---|---|---|---|
| Single ended ADC, pins ADC- and ADC+ | Min | Typical | Max |
|---|---|---|---|
| SENSE, pins SENSE- and SENSE+ | Min | Typical | Max |
|---|---|---|---|
| EXPANSION PORT POWER SUPPLY | Min | Typical | Max |
|---|---|---|---|
| Pin | Description | Minimun Rating | Maximum Rating |
|---|---|---|---|
| Pin | Description |
|---|---|
| UART | Min | Typical | Max |
|---|---|---|---|
| DIGITAL I/O | Min | Typical | Max |
|---|---|---|---|
| Differential ADC, pins ADC- and ADC+ | Min | Typical | Max |
|---|---|---|---|
| Single ended ADC, pins ADC- and ADC+ | Min | Typical | Max |
|---|---|---|---|
| SENSE, pins SENSE- and SENSE+ | Min | Typical | Max |
|---|---|---|---|
| EXPANSION PORT POWER SUPPLY | Min | Typical | Max |
|---|---|---|---|
| Pin | Description | Minimun Rating | Maximum Rating |
|---|---|---|---|
Bitrate
110 bps
5.25 Mbps
Digital IO operating voltage
1.2 V
Vio ⁽⁷⁾
5 V ⁽⁸⁾
VIL Low-level input voltage. VIL
Vio*0.2V
VIH High-level input voltage
Vio*0.8V
Imax, Max sink/source current (total for GPIOs)
-10 mA
10 mA
Voltage input
0 V
5 V
Shunt voltage range
-81.9175 mV
81.2 mV
Resolution
2.5 µV
Accuracy
±(0.1% + 10 µV)
Input impedance
220 kΩ
Voltage input
0 V
5 V
Resolution
1.25 mV
Accuracy
±(0.1% + 7.5mV)
Input impedance
830 kΩ
Voltage input
0 V
5 V
Resolution
1.5 mV
Accuracy
1%
Input impedance
1 MΩ
Output voltage
5 V
Output current
500 mA
GPI1
Digital Input #1
0 V
5.5 V
GPO1
Digital Output #1
0 V
5.5 V
GPI2
Digital Input #2
0 V
5.5 V
GPO2
Digital Output #2
0 V
5.5 V
SENSE+
Analogue
0 V
5.5 V
SENSE-
Analogue
0 V
5.5 V
ADC+
Analogue
0 V
5.5 V
ADC-
Analogue
0 V
5.5 V
RX / GPI3
UART RX / Additional Digital Input #3 (exclusively under scripting)
TX / GPO3
UART TX / Additional Digital Output #3 (exclusively under scripting)
GPI1
Digital Input #1
GPO1
Digital Output #1
GPI2
Digital Input #2
GPO2
Digital Output #2
SENSE+
Analog input with the AGND as reference/return.
SENSE-
Analog input with the AGND as reference/return.
ADC+
Differential input for current measurement. It also measures single-ended voltage with respect to AGND. Connect this input to the high side of the external shunt resistor
ADC-
Differential input for current measurement. Connect this input to the low side of the external shunt resistor
AGND
Analog ground. Return current / reference point for analog measuring.
DGND
Digital ground. Return current / reference point for digital signals.
0-15V
Adjustable output between 0V and 15V, max 600mA
Bitrate
50 bps
5.25 Mbps
Digital IO operating voltage
1.2 V
Vio ⁽⁷⁾
5 V
VIL Low-level input voltage
Vio*0.2V
VIH High-level input voltage
Vio*0.8V
Imax, Max sink/source current (total for GPIOs)
-10 mA
10 mA
Voltage input
-10 V
25 V
Shunt voltage range
-102.4mV
102.4mV
Resolution
12.2nV
Accuracy
±(0.1% + 1µV)
Input impedance
>100Mohm
Voltage input
-10 V
25 V
Resolution
3.1µV
Accuracy
±(0.1% + 250 µV)
Input impedance
>100Mohm
Voltage input
-10V
25 V
Resolution
3.1µV
Accuracy
±(0.1% + 250µV)
Input impedance
>100Mohm
Output voltage
0V
15V
Output voltage setting resolution
5mV
Output current
600mA
Voltage between USB/DC jack & DGND/AGND
-200V ⁽²⁻³⁾
-200V ⁽²⁻³⁾
GPI1
Digital Input #1
0 V
5.5 V
GPO1
Digital Output #1
0 V
5.5 V
GPI2
Digital Input #2
0 V
5.5 V
GPO2
Digital Output #2
0 V
5.5 V
SENSE+
Analogue
-10 V
25 V
SENSE-
Analogue
-10 V
25 V
ADC+
Analogue
-10 V
25 V
ADC-
Analogue
-10 V
25 V
Hardware
Otii hardware: Otii Arc Pro, or Otii Ace Pro.
DUT
Shunt resistor – How to choose the resistor?
Banana connectors cables + jumper wires
Software
RX
UART RX / Additional Digital Input (exclusively under scripting).
TX
UART TX / Additional Digital Output (exclusively under scripting).
GPI1
Digital Input #1
GPO1
Digital Output #1
GPI2
Digital Input #2
GPO2
Digital Output #2
SENSE+
Analog input with the AGND as reference/return.
SENSE-
Analog input with the AGND as reference/return.
ADC+
Differential input for current measurement. It also measures single-ended voltage with respect to AGND. Connect this input to the high side of the external shunt resistor
ADC-
Differential input for current measurement. Connect this input to the low side of the external shunt resistor
AGND
Analog ground. Return current / reference point for analog measuring.
DGND
Digital ground. Return current / reference point for digital signals.
+5V
5 V output (max 500 mA).
