I am currently working on a project of mine that has a section of it that pretty much is a precision DVM.
The goal is to use a Linear Technology LTC2440 24 bit ADC to take precise voltage readings (down to the uV is possible) and send them (via SPI) through a Microcontroller to an LCD. I am currently working to design the Analog front end stuff. I would like it to have a similar impedance to a Multimeter (10M Ohms). I accomplished this with the help of a user on a different forum that pointed me in the direction of a constant current voltage divider (9M, 900k, 90k, and 10k ohm resistors in series). I may change the ranges later but I'm trying to get something functional first.
I'm new to op amps so I was wondering if someone would like to help me with the signal path up to the ADC. (several ideas have came to me on this, the possibility of using opamps, Autorange vs Manual range, cascaded window comparators, ect.) I have a basic understanding of how op amps work but if this thing measures to 2 uV then its pretty sensitive stuff and I can already see its going to need additional measures against noise and stuff too.
If a standard set of ranges cant work, I would imagine using something like:
0-2.5V, (measuring sensors and stuff)
0-5V, (Mainly logic level monitoring)
0-12V, (DC motors and above logic devices)
0-15V, (Automotive Electrical measurements)
0-25V,
0-150V, Mains Level measurements
0-250V, Mains Level measurements
and 0-1000V Max range. May not be used much but just to have something for higher potentials.
I'm open to all input on this, I'm no master of electronics, just a long time hobbyist that may know a few things lol.
The goal is to use a Linear Technology LTC2440 24 bit ADC to take precise voltage readings (down to the uV is possible) and send them (via SPI) through a Microcontroller to an LCD. I am currently working to design the Analog front end stuff. I would like it to have a similar impedance to a Multimeter (10M Ohms). I accomplished this with the help of a user on a different forum that pointed me in the direction of a constant current voltage divider (9M, 900k, 90k, and 10k ohm resistors in series). I may change the ranges later but I'm trying to get something functional first.
I'm new to op amps so I was wondering if someone would like to help me with the signal path up to the ADC. (several ideas have came to me on this, the possibility of using opamps, Autorange vs Manual range, cascaded window comparators, ect.) I have a basic understanding of how op amps work but if this thing measures to 2 uV then its pretty sensitive stuff and I can already see its going to need additional measures against noise and stuff too.
If a standard set of ranges cant work, I would imagine using something like:
0-2.5V, (measuring sensors and stuff)
0-5V, (Mainly logic level monitoring)
0-12V, (DC motors and above logic devices)
0-15V, (Automotive Electrical measurements)
0-25V,
0-150V, Mains Level measurements
0-250V, Mains Level measurements
and 0-1000V Max range. May not be used much but just to have something for higher potentials.
I'm open to all input on this, I'm no master of electronics, just a long time hobbyist that may know a few things lol.