New to A/D MAX1231

[Guest]

First Iknow this is a PIC forum but I have posed this question on a so called elctronics forum and nobody replied, I have been here a few times and alwys got help so sorry but I could do with a hand.

I'm New to A/D and I have found what I think is the chip (MAX1231) I need, but would like anyone to have a look and tell me if it won't work or I'm missing something.

I want to measure a pack of 1.5v batteries that are in series using the differential inputs and the SPI interface to a PIC. the configuration would be like this.

AIN0 - GND of 1st batt
AIN1 - + of 1st batt
AIN2 - GND of 2nd batt, which is also + of 1st batt (basically AIN1+AIN2 tied together, etc. etc. so I'm using 8 connection to monitor 7 batteries.

Also I have another question, Will I need a external VREF of say 4v as the internal differential VREF (2.5v) appears to be -VREF/2 to +VREF/2 only giving a max of +1.25v

Hope this all makes sense.

Thx

[Guest]

Title says it all.

Thx

[SimpleAsPossible]

Is the ADC power supply isolated from the stack of batteries? It will need to be in order to use the differential inputs on a 5 V part to measure 12 V of signal.

If not, can you get away with dividing the voltages and reading the values more slowly? You'll need to decide how much current you can stand through the divider stack....note that as source impedance goes up, so must the T/H acquisition time. Hmmm...for a really slow update rate you might be able to switch a low-impedance divider stack on only when you need to take your readings....