which ADc and uC to use......

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neelam

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ad628 voltmeter

dear friends

i want to design a simple voltmeter using microcontroller( may be pic or 8051) .the range is from -200mV upto 200mV with resolution bewteen (0.01mV to 0.1mV).

which ADC to use ?wheteher i should use internal ADC or external ADC .and also which microcontroller to use. it is neccessary to do this with microcontroller .cause there are many other functions to include.

please help me out.

thankyou
neelam.
 

what you need is an ADC that can accept a +/- input or create a signal conditioner first to accept the - input.

As for the microcontroller, 8051 with built ADC is not as abundant as PIC's with ADC.
 

For 0.1 resolution you can use 16-bit conversion whereas for the 0.01V resolution (full range 0-5V) you will need a 24-bit ADC (examples :AD7714, ADS1210, ..). What you can do is to reject 4 LSbs what will give you 20-bit conversion.
Input signal should be buffered by a good instrumentation amplifier and the same buffer can be used for conversion from -/+200 to 0-400mV.

If you go for 16-bit you can have a look at MSC1201 ( https://focus.ti.com/lit/ds/symlink/msc1202y2.pdf ).
This one has improved 8051 core and built-in 16-bit ADC ..
 

thanks for replying IanP
i will be using 89C51 with external 16 bit ADC for 0.01 V resolution.

which instrumentation amplifier to use?
and also please refer me some examples.

thanks
neelam
 

Hi neelam,
Go to Silabs website they have low pincount MCU with ADC and DAC built-in with up to 24 channels. They also have very nice start kit at low cost too.
 

I would strongly recommend opamp from Analog Devices such as AD624.
( https://www.analog.com/UploadedFiles/Data_Sheets/788598335AD624_c.pdf )
In the above data sheet you will find a lot of examples on how to use this gismo.
On top of that, Analog Devices still supports the "Sample" program .. so for your single application you can have it for free ..
 

Hello

use MSP430f1xxxx here is a link to ap note - design a low cost high res voltmeter

3000 mV

h**p://focus.ti.com/docs/mcu/catalog/resources/appnoteabstract.jhtml?familyId=342&abstractName=slaa104

All the best


bobi
 

hi ianp will instrumenatition amplifier AD628 work for this project? as AD624 isn't available in my area.

Thanks
 

Look mout for the Mikroconverter - a combination of a high resolution adc and a simple µC (8052). Analog Device has good devices --> lADuC841 ord 814. So you have only one chip!
 

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