We are using PIC32MZ series Microcontrollers for our energy based application where we are measuring voltage and current for electric consumers. One single meter can monitor current for upto 10 consumers hence we used multiple pin interface to the ADC. The current ADC resolution is 12 bits which I guess is fine.
Now what I read online, Sigma Delta ADCs are suited better to measure power esp in low frequency range because they give more accurate reading and they can filter out noise from transmission lines. The problem is most MCU come with SAR ADCs (which work fine generally) but in our case I think Sigma Delta would suit us better, the problem is Sigma Delta are usually dedicated and does not have channels (we need 12 channels at least).
What is your proposed solution in my case? My question is, it is worth going from SAR to Sigma Delta for better accuracy and secondly would it is feasible design if I add an external MUX IC to I can use the same Sigma Delta for 10+ channels? This Pic MCU PIC24FJ64GC006 comes with sigma delta ADC with sampling rate of 244 to 62.5 Ksps. For single channel, I am ok with 6.4KHz sample rate per channel. Thanks
Best Answer
I'm not sure why no one brought up the STM32F373 with THREE 16bit Sigma-Delta that can do simultaneous conversions at 50Ksps single or multiplex them at 16.5Ksps(21 single ended channels or 11 differential channels), plus a 12bit 1Msps SAR ADC. ST has a App Note about using it for a power meter and they use the SDADCs for current and the SAR ADC for voltage. It has floating point + DSP at a 72Mhz. Plus 2 12bit 1Msps DACs, 2 RR analog comps, 15 timers, USB, CAN, etc. All the ADCs can be triggered from the same timer/source.
I'm using one to make a LCR/ESR meter. Right now I'm trying to see if I can use one of the DACs for the excitation voltage or have to go with an external DDS.