Wide range current measurement using ucurrent gold - Page 1
Forum section: electronics / testgear

author: krish2487
author_rank: Frequent Contributor
timestamp: July 02, 2018, 12:57:00 pm
content: Hello all,I apologise for creating a another topic with a much addressed topic like the ucurrent..I was also unsure as to which sub forum would this be an appropriate topic to post..I need help addressing an issue with ucurrent gold and ESP32.A product I am working on uses an ESP32, RFM69 and bunch of other semiconductors.The maximum power draw components are the ESP32 and the RFM69 radio. Other components are mostly sub 1mA consumption.I have been using one of these cheap USB power meters to measure the current draw.I am able to see that the board consumes about 200 mA (ESP32 + RFM69) during peak transmission and wifi communication.However, the board also goes to low power sleep mode for the majority of the time.I need to measure the maximum (no issue with the usb power meter) and the minimum ( the usb power meter has a resolution of 1mA).I am certain given the firmware, the board consumes less than 1mA but I need stable numbers.(This is for sizing batteries for the application and/or hardware/firmware changes)Given the wide range of currents to measure, I bought a ucurrent assuming that I might be able to measure the maximum and minimum current.but realised in retrospect that given the shunt resistors in the nA and uA range, I might be starving the processor of the power to even startup and run..I did this after the 3.3V regulator on the board, which powers up the devices. inserted the ucurrent in series with the + supply and measured the output voltageAny suggestions on what I can do to measure the current in sleep mode??Thanks in advance!! :-)

author: Fungus
author_rank: Super Contributor
timestamp: July 02, 2018, 01:23:17 pm
content: Quote from: krish2487 on July 02, 2018, 12:57:00 pmMaybe I'm missing something obvious, but.... put it to sleep and measure it with a multimeter?If you put in a closed switch which bypasses the multimeter you run it normally. When you want to take a current reading you open the switch and force the electrons to go through the meter instead, this lets you count them.An ordinary multimeter with suitable mA/uA range will probably do it, no need for uCurrent.(although the same technique will work with uCurrent as well)

author: krish2487
author_rank: Frequent Contributor
timestamp: July 02, 2018, 01:27:21 pm
content: I am sorry, I should have been more verbose in explaining the issue.The On time is variable. and there is no display to indicate what mode it is operating in (run or sleep).The board has a bidirectional communication with a server and then sleeps.No manual way of putting the board to sleep.I guess I could always wait sufficient time and then switch the ucurrent to the uA range.

author: Kean
author_rank: Unknown
timestamp: July 02, 2018, 01:49:57 pm
content: A Schottky diode across the shunt resistor will limit the burden voltage at high current on low ranges. Not a perfect solution, but it may work for you.Is customised firmware not possible for the sleep mode tests? I don't imagine it needs to be highly customised.

author: krish2487
author_rank: Frequent Contributor
timestamp: July 02, 2018, 01:53:55 pm
content: @keanThank you for the Schottky diode idea.Customized firmware is possible.Maybe just a firmware that does nothing but sleep and then measure the current consumption.:-)Thank you!

author: Fungus
author_rank: Super Contributor
timestamp: July 02, 2018, 01:59:33 pm
content: Quote from: krish2487 on July 02, 2018, 01:27:21 pmYep. Put the multimeter/uCurrent in the circuit, reading uA, with a closed switch bypassing it (crocodile clip, whatever...)When the reading on your USB power meter drops below 1mA you simply open the switch and take a reading on the multimeter.

author: krish2487
author_rank: Frequent Contributor
timestamp: July 02, 2018, 02:01:39 pm
content: Indeed,it never struck me to use the USB power meter in conjunction with the ucurrent to switch ranges..definitely a time saver ! :-)Thank you @fungus.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: July 04, 2018, 10:21:45 pm
content: Quote from: krish2487 on July 02, 2018, 12:57:00 pmDoesn't the ucurrent gold specifically have a shorting switch on it for changing ranges without opening the circuit? So you run the DUT on ma range until it sleeps, hold the short switch, then switch to uA or nA and then switch the shorting switch back to on.