LAUNCHXL-CC2640R2: Current Measurement using 2 AA Batteries as Power Supply?

Markel Robregado

Part Number: LAUNCHXL-CC2640R2
Other Parts Discussed in Thread: CC2640R2F

Hi,

At my previous work I have done CC2640R2F Launchpad current measurement using Adjustable Power Supply and Fluke Digital Multimeter and I was able to get expected current measurements.

Now, I am trying to do the same CC2640R2F Launchpad current measurement using 2 AA Batteries Power Supply and Keysight U1232A Multimeter and I am encountering problems. I am using Pin Shutdown Example Program from SDK 2.20. I remove all jumpers except the led jumpers. I power the CC2640R2F Launchpad and it works as expected from just visually observing.

When I connect the Keysight U1232A Multimeter in series to measure the current, the CC2640R2F Launcpad red led does not turn on and the current measurement read is 500uA. I use another digital multimeter to measure the 3.3V at the CC2640R2F Launchpad and I read 1.6V.

The difference before is that I use a Adjustable Power Supply with constant 3.3V and now I use 2 AA batteries power supply.

Is the cause of my problem the use of 2 AA batteries as power supply?

-kel

over 7 years ago

0 IUsedToBeARealPerson (M-W) over 7 years ago

TI__Guru 58425 points

Hi Markel,

At what range are you measuring when seeing this, uA range? Have you in this case tried to switch to a higher current range to see if it starts as expected?

0 Markel Robregado over 7 years ago in reply to IUsedToBeARealPerson (M-W)

Guru 86785 points

Hi M-W,

The range is set to auto and I see the range at 600uA. This is the first time I am using this Keysight U1232A Multimeter. I bought this specifically to measure the Standby Current and Shutdown Current of CC2640R2F. I see at it's datasheet that it can measure .01uA

What is very unusual is that when I connect this Multimeter for current measurement the CC640R2F Launchpad red led is off meaning the Pin Shutdown example program is not running.

-kel

0 IUsedToBeARealPerson (M-W) over 7 years ago in reply to Markel Robregado

TI__Guru 58425 points

Hi,

As the multimeter has uA and A range to select between, If you switch to the full "A" range (putting the resolution aside for now) does it work?

0 Markel Robregado over 7 years ago in reply to IUsedToBeARealPerson (M-W)

Guru 86785 points

Hi M-W,

When I set to A it works I can see visually that Pin Shutdown Example Program works. The reason I bought this Keysight U1232A is to be able to measure Standby and Shutdown Current. This is the cheapest I can find online that can measure 0.01uA.

-kel

0 IUsedToBeARealPerson (M-W) over 7 years ago in reply to Markel Robregado

TI__Guru 58425 points

Hi Markel,

I've seen this with some multimeters while some others would work just fine. I suspect this is related to some current limit in the uA mode that will cause a larger voltage drop when the current is exceeded but I can't say that for sure.

I have been doing reading with a relative cheep UNI-T UT61E meter and it has worked quite well.

0 Markel Robregado over 7 years ago in reply to IUsedToBeARealPerson (M-W)

Guru 86785 points

Hi M-W,

Thanks for your replies. I am very disappointed with purchasing this Digital Multimeter. It is clearly mentioned at the users guide that it can measure 0.01uA. If it causes the Launchpad to not work, then I can only conclude that this Keysight Digital Multimeter I have now is defective and I am going to get a replacement or get a refund.

-kel

0 IUsedToBeARealPerson (M-W) over 7 years ago in reply to Markel Robregado

TI__Guru 58425 points

Hi Kel,

I would guess it can indeed measure at that accuracy, I think the question really is what the supported current range is when measuring in uA resolution. As the device would toggle between ~1uA and several mA, the range it would have to cover in a single mode is quite large.

What happens when you reach the upper limit of the range is the real question. Like in this case, are the multimeter suppose to not impact the circuit and simply give a false reading, or will you have an increased drop over the meter when you exceed the limit mot the mode?

0 Markel Robregado over 7 years ago in reply to IUsedToBeARealPerson (M-W)

Guru 86785 points

Hi M-W,

Anyway, I never give up at the end I came up with a working procedure.

1. Connect red probe to A port.
2. Set dial to measure Ampere.
3. Power on CC640R2F Launchpad. I see the red led on meaning Pin Shutdown is working.
4. Press right button to go to shutdown mode.
5. Move red probe from A to uA port.
6. Set dial to measure uA.

After step 6 I read .08uA and going down, which is the Shutdown Current.

-kel

0 IUsedToBeARealPerson (M-W) over 7 years ago in reply to Markel Robregado

TI__Guru 58425 points

Hi Kel,

Glad to hear you found a work around that worked for you! Good luck with what ever follow this :)

0 Markel Robregado over 7 years ago in reply to IUsedToBeARealPerson (M-W)

Guru 86785 points

Using Keysight U1232A for mA to uA current measurement is troublesome . But, it is good enough for what I need to do.

Compared to the Fluke 287 that I used before at work. I just connect the probe to uA port and I can see the current change from mA to uA and vice versa without problems.

-kel

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LAUNCHXL-CC2640R2: Current Measurement using 2 AA Batteries as Power Supply?