Current measurement for Embedded system - Page 1
Forum section: electronics / beginners

author: jacobchanjal@gmail.com
author_rank: Newbie
timestamp: October 29, 2012, 01:02:24 am
content: Hello Everyone,I am a System Test engineer with a new job in an Embedded system development company. I am trying to perform Battery characterization for our product as my initial task. Let me give you all a brief idea about the project.The product has two PCB boards.1. Battery Pack PCB2.Embedded system module PCB(containing modules for GSM,WIfi and Sub gig communication)My initial task is to measure current consumption of the embedded system at various function . I have come up with a certain plan to modularize the functionality of the embedded system. Now i need to measure the current consumptionI have come up with an idea to use a shunt resistor between the battery pack and the embedded module. I am planning to design a PCB with current sense resistor(around 0.01 ohm) and ZXCT 1009. I need advice on the way I am proceeding.1. Is this the proper way of measuring current in an embedded system( sleep mode current consumption is 165uA and during work mode it goes to 30mA)2. I need help in designing the PCB with current sense resistor along with any IC so that I can measure using my Tek MSO 3014 oscilloscope and Keithley DMM (6 1/2)Thank you for reading and hope to learn from your comments soon.

author: notsob
author_rank: Frequent Contributor
timestamp: October 29, 2012, 01:12:17 am
content: craftycoder ( a member of eevblog) has an example that may suit youhttp://blog.freesideatlanta.org/2012/08/precision-low-current-measurement-w.html

author: jacobchanjal@gmail.com
author_rank: Newbie
timestamp: October 29, 2012, 01:25:27 am
content: Thanks for the link. But I am specifically looking for current shunt resistor method to find out the current consumption.

author: robrenz
author_rank: Super Contributor
timestamp: October 29, 2012, 02:14:08 am
content: Why aren't you just measuring the voltage drop across the resistor with the 6.5digit DMM? At 0.1µV it would give you 10µA resolution.

author: jacobchanjal@gmail.com
author_rank: Newbie
timestamp: October 29, 2012, 03:19:05 am
content: So you mean to say there is no need for ZXCT 1009 IC?If so, Am I choosing the right current sense resistor value? Is there a way in which I can bring up with a PCB with these components pretty soon for testing?

author: robrenz
author_rank: Super Contributor
timestamp: October 29, 2012, 11:52:55 am
content: You do not need anything but the DMM to measure the voltage drop of the shunt resistor.I dont't mean to be rude but your questions make me wonder if you are trying to have the forum design something for you that is way beyond your current electrical knowledge. most members like to help out, but dont like doing someones job for them. If this does not apply to you my appologies.

author: BravoV
author_rank: Super Contributor
timestamp: October 29, 2012, 12:21:10 pm
content: Its obvious the op doesn't even understand the basic ohm law.Hint :https://www.eevblog.com/forum/general-chat/current-sense-resistor/

author: jacobchanjal@gmail.com
author_rank: Newbie
timestamp: October 29, 2012, 10:33:11 pm
content: I admit that. That is the reason why I am trying to clarify my understanding, If you guys allow me to continue.

author: robrenz
author_rank: Super Contributor
timestamp: October 29, 2012, 10:53:02 pm
content: From what you have described so far:Directly measure the current with the Keithley DMM. Make a simple tee jumper with suitable connectors so you can plug the keithly between the battery pack pcb and the Embedded system module PCB to measure the current draw.Read the Keithly programming manual so you can control it and take readings into your data gathering/control system.