Power measurement

When designing a battery powered product using a Particle device, it will typically be useful to do your own measurements with any additional peripherals you have added to verify the power consumption.

Measurement tools

Standard DMMs

In general, most portable DMMs that have a physical range selector are not suitable for current measurement for Particle devices.

The reason is that the large current range for cellular devices, in particular. It could be as high as 1.5 A during connection to 100 µA (0.0001 A) in sleep mode, which is beyond the range of most inexpensive meters.

If you are in the low current range and exceed the rating, burden voltage will affect the operation of the device because the voltage will be lower than the rated version.

This problem can be corrected using the µCurrent Gold.

µCurrent Gold

The µCurrent Gold works with a regular digital multi-meter and eliminates the burden voltage issue. This also requires an external power supply. Typically you would use a DC bench supply, though you could also use a battery.

• Relatively inexpensive.
• Works with tools you probably already have.

Siglent SDM3055

The Siglent SDM3055 bench DMM is suitable for measuring current usage from Particle devices because it can auto-range without interrupting the power. It can also log the data to its software for Windows over USB.

• Logs data to a computer.
• Also performs other bench DMM features.
• Requires an external power supply. Typically you would use a DC bench supply.

Qoitech Otii Arc Pro

The Qoitech Otii Arc Pro is the tool of choice at Particle. It is what the current measurements are done with.

• Logs data to a computer.
• Built in power supply.
• Can synchronize UART serial logs with the power consumption graph.

Tips for Particle devices

LiPo battery input vs. VIN

All of the current measurements are done at 3.6V to the battery input for devices with a battery input.

Devices with a bq24195 PMIC provide the lowest current only when using the LiPo battery input. This is especially important when you need low current in sleep mode. When using VIN, an additional voltage regulator within the PMIC is enabled, which has some current use even at idle. While the difference is negligible in operating mode as a percentage of total usage, in sleep mode it can be significant compared to the 100 µA sleep current on some devices.

Particle devices with a PMIC

The following devices include a PMIC.

Show devices with a PMIC

Beware of peripherals

The Particle B-Series evaluation board is not well suited for testing power consumption. The Ethernet port (WIZnet W5500) cannot be disabled, and uses a significant amount of power.

The newer M.2 breakout board does not have a built-in Ethernet port and does not exhibit this behavior.

Cellular power differences

When calculating a power budget, the cellular connection has a high degree of variability. As a general rule, in order of lowest power to highest is:

• LTE Cat M1
• LTE Cat 1 (4G)
• 3G
• 2G

In particular, on devices that can connect to 2G, the modem uses the highest current, and also takes the longest to connect. Be sure to take this into account when establishing a power budget where you may be connecting by 2G.

Comparison tool

• Current measured from the LiPo battery input at 3.6 VDC.