Low current datalogging ammeter

[BuffaloEngineer]

Are there any ammeters (or DMMs or power meters) that are higher frequency, a few MHz perhaps, that can better characterize the power consumed by a portable device? Normally our device operates between 50 and 500uA with periodic spikes that go up to 10mA. We want to characterize the power consumed with a device that's a little more accurate than our Tenma DMMs.

Thanks so much!

 

[Tony Stewart]

True RMS power meters use precise thermal measurements on an RF load resistance of 50 Ohms.

YOu want your current sense to drop as little as possible but give good SNR. Usually 50mV is pretty standard for current sensors but they lack the bandwidth you need as they tend to use trans-impedance amplifiers. But this is the fastest IC I found from D-K https://www.ti.com/product/ina225/description

You can roll your own video amp and precision rectifier or simply use a high speed DSO with 50 Ohm Coax and 50 Ohm termination at scope to prevent reflections using a 5.6 Ohm shunt to yield a net 5 Ohm shunt that is transmission line terminated to scope. THis would give 50mV peaks which with a decent scope at 5mV /div should be able to measure.

For the more elaborate test lab I would use old Tektronix differential FET Probes across the shunt R with 200MHz BW and offset adjustment.

 

[AnalogKid]

Are you trying to measure the peak or RMS current of a few MHz waveform? If so, that will be difficult as described above. Another option is to measure the power. The cell phone industry has created multi-MHz RMS chips.

https://www.linear.com/products/rf_rms_detectors

ak

 

[KeepItSimpleStupid]

You could put together a I-V converter (zero resistance ammeter) fairly easily and then use the math functions on a DSO.