Yes, as I wrote. I would not mess with AREF. At most you can only get a multiplication about 4. Use an op-amp. Signal conditioning really almost alway is required in the analog domain before any A/D conversion
Also like the uP is not inside the oven and has a cable of some length so you'd want a buffered analog signal on the cable, the op-amp can do that to. Those $2 parts I linked to have the ADC referenced to 3.3 volts but have 12 bits as compared to the arduino which has 10 bits The next step up the complexity scale would have you place an I2C interlaced ADC inside your oven. These don't cost much and have several ADC channels. then your oven has full digital interface and a much higher quality DAC. But this adds another 2 or 3 dollars to the design. Maybe worth it as now all the analog stuff is inside a temperature stable metal tin can. But you have to watch this feature-creep as you can drive up cost with little to show for it. Also I'd not want the analog stuff designed to work only with ADC built into one specific development board. The I2C serial interface is pretty much universal I'm thinking something like this: http://www.ebay.com/itm/12-Bit-I2C-4-CH-ADS1115... <http://www.ebay.com/itm/12-Bit-I2C-4-CH-ADS1115-ADS1015-Module-ADC-Development-Board-for-Arduino-/112192172479?hash=item1a1f2cb1bf:g:kQEAAOSwA3dYGrZp> Notice that the chip has programmable gain, it can scale the input over a small range before sampling. For $2 it's still a "poor man's part and you do NOT need to make a PCB to use it. On Tue, Jun 6, 2017 at 10:08 AM, Jim Harman <j99har...@gmail.com> wrote: > On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 < > ian.riley....@navy.mil> wrote: > > > Is there a practical minimum for what voltage you can feed into AREF? > > > > It is hard to find on the data sheet, but the minimum voltage for an > Arduino's AREF is the internal analog reference voltage - 1.1V for the Uno, > 2.56V for the Leonardo or Micro. The 32U4 chip in the Leo and Micro has > options for differential analog input and gains of 10, 40, or 200 but they > are not supported by the Arduino IDE - you have to set the internal > registers directly to use them. Also the input amplifier is pretty slow. > > > -- > > --Jim Harman > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.