Using PPK to measure low-side current consumption of a battery-powered device

[Boaz]

We have a setup where we want to measure the current consumption of a battery-powered device:

• The batteries are soldered to the device, and cannot be removed.
• We can only do low-side current measurement (i.e. we connect to a solder-bridge from the DUT to ground)

Is it possible to configure the PPK for this setup? If so, how should be connect the DUT?

[Stian Røed Hafskjold]

You need to somehow be able to power the device from the PPK. What if you remove the measurement resistor (leave the solder bridge open). Then power the board using the PPK, between the + terminal on the battery and on the DUT side of the solder bridge?

[Boaz]

I can't. At the stage of the test, the device is already assembled, the batteries soldered, and unfortunately there is not solder bridge to disconnect the batteries from the load.

[Stian Røed Hafskjold]

But in your question you said you had a solder bridge between DUT and ground. If it's not possible to open the solder bridge then there's no way to measure current at all?

[Boaz]

I mean, I can't connect the PPK in place of the battery (i.e. disconnect the battery from the load). I can disconnect the load from ground using the SB

[Stian Røed Hafskjold]

Yes, so if you disconnect the load from ground you basically disconnect the load from the battery as well. Then you can power the load directly from the PPK.

Like this:

Of course, if everything is inside a casing and you don't have access to anything other than the solder bridge, then you can't use the PPK to measure current unfortunately.

[Boaz]

Thanks Stian. Most helpful