SBAA051A January   1994  – April  2015 MSC1210Y2 , MSC1210Y3 , MSC1210Y4 , MSC1210Y5

 

  1.   Principles of Data Acquisition and Conversion
    1.     Trademarks
    2. 1 System Sampling Rate
      1. 1.1 Error Considerations
      2. 1.2 Aliasing Error
      3. 1.3 How Many Samples per Cycle?
      4. 1.4 Aperture Error
    3. 2 A Few A/D Converter Points
      1. 2.1 Accuracy
      2. 2.2 Selecting the Resolution
      3. 2.3 Resolution
    4. 3 Increasing System Throughput Rate
    5. 4 System Throughput Accuracy
    6. 5 Digital Codes
    7. 6 Summary

2.3 Resolution

The number of bits in an A/D converter determines the resolution of the data acquisition system. A/D converter resolution is defined as:

Equation 2. Eq02_resol_SBAA051.gif

    where

  • LSB = least significant bit
  • VFSR = full scale input voltage range
  • n = number of bits
  • D = number of decimal digits

The number of bits defines the number of digital codes and is 2n discrete digital codes for A/D converters.

For this discussion, we will use binary successive-approximation A/D converters. Table 1 shows resolutions and LSB values for typical A/D converters.

Table 1. Relationship of A/D Converter LSB Values and Resolutions for Binary Codes

A/D Converter Resolution (Binary Code) Value of 1LSB Value of 1/2LSB
Number of Bits (n) Number of Increments (2n) 0 to 10 V Range (mV) 10 V Range (mV) 0 to 10 V Range (mV) 10 V Range (mV)
16 65536 0.152 0.305 0.076 0.152
12 4096 2.44 4.88 1.22 2.44
11 2048 4.88 9.77 2.44 4.88
10 1024 9.77 19.5 4.88 9.77
9 512 19.5 39.1 9.77 19.5
8 256 39.1 78.2 19.5 39.1