Relationship between AD sampling and reference source

乱世煮酒论天下

Relationship between AD sampling and reference source [Copy link]

When sampling the embedded chip AD, it is necessary to determine the actual numerical relationship between the sampling value and the display value based on the reference voltage;
1. The reference voltage is 3V, and the sampling level is 4096 for 2^12, that is, 0-3V corresponds to 0-4095. Assuming that the software still samples according to the reference voltage of 3.3V, then 0-3V corresponds to 4095*10/11=3722, that is, the displayed value is slightly smaller than the actual value.
2. The reference voltage is 3.3V, and the sampling level is 4096 for 2^12, that is, 0-3.3V corresponds to 0-4095. Assuming that the software still samples according to the reference voltage of 3V, then 0-3.3V corresponds to 4095*11/10=4504. Of course, the sampling value remains unchanged when it reaches 4095, and there is a parallel line behind it.
I don't know if my understanding above is correct. Please advise?

littleshrimp

The first problem is that the reference voltage is 3V, and the maximum input (sampling) voltage can only be 3V. If it exceeds 3V, the CODE obtained can only be 4095. After the software obtains the CODE, it calculates the voltage. If it knows that the reference is 3V, it should calculate the voltage according to 3V/4095*CODE. If the software mistakenly thinks that the reference is 3.3, then 3.3/4095*CODE, the voltage obtained will be larger than the actual voltage, for example, 4095 should be 3V, but the calculated voltage is 3.3V.

qwqwqw2088

When AD sampling in a 32-bit microcontroller, the sampled value and displayed value are determined based on the reference voltage, and there is a relationship with the actual value. Just study this relationship.

fjdeepblue

The reference voltage is 3.3V, and the sampling level is 4096 at the power of 2^12, which means that 0-3.3V corresponds to 0-4095. This is correct. If the software calculates according to 3V, the result will be smaller than the actual value. 0-3.3V corresponds to 4095*11/10=4504, which is the result of software calculation. It will not "remain unchanged after the sampling value reaches 4095". The sampling value of the ADC remains unchanged after reaching 4095.