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Current Sense Amplifier and uController

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anniemanuja

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Hello

I need to design a system to monitor current on approx 40 voltage rails. I will be using an Rsense + Current amplifier on each rail but I cannot send all outputs of Current amplifier directly to ADC in uController as I am not aware of any part with 40 channels. What I am thinking is to use Analog mux and send o/p of CSA to AMUX and then outputs of AMUX to ADC channles on uC.

Could any suggest any other way to do this? Also, can anyone suggest microcontroller and AMUX for this design? The voltage rails are between 0.5V to 5V and CSA should be able to measure current in range of couple of 100mA to 2A.

Thank you

Ann
 

Hi Ann,

If Cost is not a constraint you can choose

34908A 40 Channel Single-Ended Multiplexer Module. See the below site for more information.
http://www.home.agilent.com/agilent/product.jspx?pn=34908A&NEWCCLC=USeng


OR

There are plenty of 16 channel Multiplexers(Ex:TI CD74HCT4067) are available in the market and AVR Series Microcontroller can be used for this application.

Regards,
Viswanath
 

Hello Viswanath

Thank you so much for your reply.

Cost is always a constraint :).

Could you please tell me does it matter to use an external 16bit ADC or a 16-bit ADC internal to uP? Also, which is more precise a Sigma Delta ADC or a SAR?

Besides are you aware of any part which is 16:1AMUX+ADC on a single chip?

Thanks

Ann
 

Hi Ann

It depend on the accuracy of measurement external A2D converter used with external ref voltage is all ways more accurate then uC internal A2D

Whether high accuracy is not an issue you can use a micro with 8 ch ADC (STM32..etc have 12 bit ADC)
who use an external Vref (100 QFP and up) and put 74HC4051 (8:1 mux) on each ADC channel to get a maximum of 64 mux'd channels and low cost solution.

All the best

Bobi

The microcontroller specialist
 

anniemanuja said:
...which is more precise a Sigma Delta ADC or a SAR?...
Click to expand...
Hi Ann,
SAR & Sigma Delta converters are basically different families, so is the most precise SAR ADC that I know a 18 Bit type, S-D are usually 24 Bit (ev. more) devices...
You can have a 18 Bit SAR ADC with 1Channel at 1 Msps, the highest speed S-D that I know is at 1Ksps (maybe w. 4 channels)...
K.
 

@Vishwanath : Have you used this Agilent system you mentioned? How good is it in terms of accuracy? If given scope probably apart from the complete I develop, I can fed all rails to this agilent in parallel for a good comparison of results. What is your opinion?

@ Bobi and Ks ...Thank you so much to all! I am doing some research on these solutions you mentioned and definetely will let you know if I have any question. Thank you once again!
 

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