Sonsivri
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
December 08, 2016, 05:05:46 17:05


Login with username, password and session length


Pages: [1]
Print
Author Topic: Low current measuring  (Read 1251 times)
0 Members and 1 Guest are viewing this topic.
free
Active Member
***
Offline Offline

Posts: 115

Thank You
-Given: 66
-Receive: 13


« on: April 19, 2010, 03:42:09 03:42 »

hi friends,

I need your help.
I want to measure low current, ac bipolar squarewave from 0 to 20mA, 75Hz.
What is a good method for it with precision result?
Thanks in advance.

Logged

Some dream to escape reality, some to change it forever.
- Soichiro Honda -
LabVIEWguru
Senior Member
****
Offline Offline

Posts: 267

Thank You
-Given: 223
-Receive: 553



« Reply #1 on: April 19, 2010, 05:43:15 05:43 »

you could put a 250 ohm resistor across the 20 ma = 5 volt with a scope or dvm
If you want to measure it with an A/D use an op-amp to offset it "up" to all positive into an A/D
almost anything will digitize at 75 Hz
Logged
vovchik02
Junior Member
**
Offline Offline

Posts: 61

Thank You
-Given: 43
-Receive: 11



« Reply #2 on: April 19, 2010, 06:43:49 06:43 »

Look on HCPL7800 (or analog) 10 Om shunt on input , optical isolated bipolar out .
Logged
DreamCat
Active Member
***
Offline Offline

Posts: 235

Thank You
-Given: 130
-Receive: 77



« Reply #3 on: April 19, 2010, 10:10:29 10:10 »

which kind value you want to measure? peak current or average current value ?
these need difference method.
Logged

May be I expressed the wrong meaning, sorry for my bad english. Please correct it for me if you can.
free
Active Member
***
Offline Offline

Posts: 115

Thank You
-Given: 66
-Receive: 13


« Reply #4 on: April 20, 2010, 03:00:13 03:00 »

Sorry for the delay. I have the problem with my connection. 
I want to measure only the peak value.
Logged

Some dream to escape reality, some to change it forever.
- Soichiro Honda -
DreamCat
Active Member
***
Offline Offline

Posts: 235

Thank You
-Given: 130
-Receive: 77



« Reply #5 on: April 20, 2010, 06:11:43 06:11 »

like LabVIEWguru said , you can use a resistor convert it to voltage, and use A/D converter get the peak voltage. this need very fast.

or you can peak voltage detector got it. there is many peak voltage schematic you can search.

http://images.google.com.hk/images?q=peak%20voltage%20detect
Logged

May be I expressed the wrong meaning, sorry for my bad english. Please correct it for me if you can.
free
Active Member
***
Offline Offline

Posts: 115

Thank You
-Given: 66
-Receive: 13


« Reply #6 on: April 21, 2010, 04:33:43 04:33 »

I am building some circuit for it.
Logged

Some dream to escape reality, some to change it forever.
- Soichiro Honda -
Pages: [1]
Print
Jump to:  


DISCLAIMER
WE DONT HOST ANY ILLEGAL FILES ON THE SERVER
USE CONTACT US TO REPORT ILLEGAL FILES
ADMINISTRATORS CANNOT BE HELD RESPONSIBLE FOR USERS POSTS AND LINKS

... Copyright 2003-2999 Sonsivri.to ...
Powered by SMF 1.1.18 | SMF © 2006-2009, Simple Machines LLC | HarzeM Dilber MC