Serial ADC interfacing

[dayal]

Hi,

How i can interface the serial ADC for my project, the input is 0.00mV to 0.630 mV, and i need the Corresponding Digital output. And how i can give the Very few milivolts to the input to the ADC.

 

[laktronics]

Hi,
Getting a very low signal is not the problem, almost all sensors produce even smaller signals and the real problem is to amplify them with out losing accuracy. For testing purpose, you can use a forward biased silicon diode like 1N4148 and connect a parallel multiturn wirewound potentiometer of 500 ohms across it. Which ADC are you using?
Regards,
Laktronics

 

[dfullmer]

Hi Dayal,

First I would bump up the 0.63 v signal with an op amp. Say boost it by 7-8 times. Then feed this signal into the ADC with a 5 volt reference . This way you will get more resolution on the signal. Use SPI interface on the ADC to a PIC or stamp 8 bit controller. Lots of sample code availible out there.

Regards

dfullmer

 

[FvM]

Hello,

for 0.63 mV signal span, a separate amplifier would be normally the preferred solution. You should define also the intended resolution and bandwith respectively sampling rate.

In some cases, particularly for low speed measurements, it may be also possible to use an "internal amplified" ADC, e. g. a TI or Analog Devices Sigma-Delta converter. A 16-bit converter with a 10 mV span would have still 12-bit resolution with your signal range. Utilizing autozero features, offset and offset drift are lower as with a conventional OP.

Regards,
Frank