Hi,
I have a rectifier circuit which im using to measure an AC current via a hall sensor (ACS714). As I want to measure a simple DC I have a strong low pass filter, or rectifier (a series diode with a 10uF capacitance). I use a circuit as advised in the ACs714 data sheet (although I add an amplifier gain stage after the sensor before the rectifier. This sensor works well... until I arrive at the input of my microcontroller (STM32) ADC...
http://imageshack.us/photo/my-images/607/acs714appcircuit.png/
The (12bit) ADC seems to force a value of Vref/2 at the pin, and returns a sample of 0x0800. I have tested the ADC by applying voltage, via a potentiometer and it works fine.
Is there a problem with having the huge capacitance to ground at the input of the ADC or perhaps the diode? Any suggestions how I can sample my sensor voltage properly?
Tnx
I have a rectifier circuit which im using to measure an AC current via a hall sensor (ACS714). As I want to measure a simple DC I have a strong low pass filter, or rectifier (a series diode with a 10uF capacitance). I use a circuit as advised in the ACs714 data sheet (although I add an amplifier gain stage after the sensor before the rectifier. This sensor works well... until I arrive at the input of my microcontroller (STM32) ADC...
http://imageshack.us/photo/my-images/607/acs714appcircuit.png/
The (12bit) ADC seems to force a value of Vref/2 at the pin, and returns a sample of 0x0800. I have tested the ADC by applying voltage, via a potentiometer and it works fine.
Is there a problem with having the huge capacitance to ground at the input of the ADC or perhaps the diode? Any suggestions how I can sample my sensor voltage properly?
Tnx