Current Sensing Circuit Concepts and Fundamentals

7/20/2010 12:37 PM EDT

I personally think this is just an entry level circuit discussion article with very limited information. The article just mention about the sense resistor approach while there are indeed many other current methods that wasn't discussed. Besides, building instrumentation amplifier (IA) with discrete op-amp is not as easy as the simple equations. There are many other practical stuff (including layout) that must be considered. There are many monolithic IA that can do a much better. For high side sensing, there are also some specially design current sense amplifiers that are even better then an IA.

8/18/2010 7:31 AM EDT

thanks

8/19/2010 2:48 AM EDT

hi whether it is possible to connect this circuit with an wireless network

8/25/2010 5:54 AM EDT

I concur with GREAT-Terry. This article barely passes as students' term paper. Not mentioning dedicated products for current measurement is unacceptable. On the positive side, this is at least an objective article rather than the sale pitch by Maxim pointed out by Asho_#1.

8/25/2010 8:26 AM EDT

Whereas the resistor approach may be fine for some applications, I implemented a better solution for my 300KHz, +/-150V, 1000W half bridge application. A small gapped powdered iron core with a hall effect sensor stuck in the gap with a few windings (opposite directions)worked great and was cheap. Put this module in between the high & low side FETs on the output of the bridge to measure bridge current in either direction. The Hall Effect sensor output fed into a general purpose ground-referenced op amp to scale the voltage to whatever you needed. It was fast enough to use for overcurrent protection, didn't introduce any additional resistance, and generated a nice robust output voltage in proportion to the bidirectional half-bridge current.

8/26/2010 2:42 AM EDT

Here's a simple and cost-effective solution to high-side current sensing. http://www.supertex.com/pdf/datasheets/HV7801.pdf
No complex instrumentation amps needed!

8/27/2010 1:35 PM EDT

For a kid right out of college, this article may confirm that the basic op-amp circuits he learned are valid. For real-world applications however, the article does not educate the reader. Problem areas such as the inductance of low-R CS resistors when used for high-bandwidth sensing, for example, are not even mentioned.

9/1/2010 1:40 PM EDT

Thank You

9/19/2010 3:55 PM EDT

Good article for entry-level graduate to play with some simulator such as LTspice or other spice simulator to get more indepth knowledge of circuits.

9/22/2010 2:51 PM EDT

Really good article thanks!

9/22/2010 3:34 PM EDT

I would like to thank both the poster of this article and those who contributed both pointers and questions! It really helps to get multiple points of view on a subject. Reading the application note and following the other links gave me a better appreciation for what designers are up against.

9/23/2010 8:23 PM EDT

Exide has been using low side sesnsin in their automotive battery chargers for years.

11/21/2010 10:16 AM EST

Even though simple and fundamental, I believe the article is worth reading, especially for someone who is not so familiar with the analog aspect of designs.

12/13/2010 1:46 PM EST

I would say a nice general overview of current sensing topologies, thanks! I wonder how much the circuit outputs would be affected by say high frequency switching (say PWM based motor control) and back EMF from motor operation. Would filtering be needed or just helpful in these situations with motors/PWM switching?

1/21/2011 4:27 PM EST

I am not sure what the author means by "low to medium current" but for the past 100 years, companies like Weston and Simpson have been making current sensing shunts with full scale voltage drops of 50 mV for for current ranges up to at least 1000 amps.

9/4/2011 3:29 PM EDT

The article is very good and helpful, many guys just overlooked the fudamentals which actually is the most important thing.

Thanks for the posting.