MCP3428 Cant read more of 2048 Volts


#1

Hello.

I am using MCP3428.

When I use with a 1.5V battery Its work great.

But If appli over 2.048V I get always same read (2047 raw).

I read in the description of the item that capable of monitoring a full scale range of 4.096VDC or ±2.048v differentially.

My question is how can I read up 4.096 ?
I have to send some command to change to taht mode?
I have to use resistors ?


#2

From what I recall, the MCP3428 has a gain setting. Look carefully at this setting in the datasheet for the MCP3428, this will directly control the voltage range. This chip has several nice features that may be useful to you.
Hope this helps.
Ryan


#3

The description of a full scale range of 4.096VDC or ±2.048v means you cant measure anything over (+) 2.048V, correct ?
The MCP3428 has an on-board 2.048V reference voltage.
The measurement Range is from (-) 2.048 to (+) 2.048 = 4.096 Full Scale Range.

This range is also reduced by the gain setting (PGA), as @ryan mentioned.
Full Scale Range = 4.096/PGA
Example: If you had an extremely weak signal and wanted 8X gain-
(-) 0.256V to (+) 0.256V = Full Scale Range.

You would need to bias the voltage that you want to measure if it’s higher than (+) 2.048V, since that’s the reference voltage.
I wouldn’t be scared of a simple 1:1 voltage divider for a (+) 4.0V measurement, it’s a 16-bit device :grinning:


#4

Absolutely, we use dividers all the time to optimize range into ADCs. Thanks for the details @rfontaine.


#5

Thanks both for the clarification.

I will add voltage divider.

Heve nice day.