Diamond Systems ELTON ELT-BB01, User Manual

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Elton User Manual Rev 1.04 www.diamondsystems.com Page 49
Although the native A/D resolution is 12-bits, the SAM microcontroller contains an innovative feature that
enables higher resolution by averaging several samples. This technique enables the resolution to be
configured to 16-bits.
Oversampling and averaging can be used to:

Increase measurement resolution.

Improve the Signal-to-Noise Ratio (SNR) and measurement resolution reduced throughput.

Improve SNR
for “white” noise.

Reduce noise while maintaining a 12-bit resolution.
The disadvantages of averaging samples are an increased CPU utilization that results in each individual A/D
measurement taking longer to compute and a reduced maximum sampling rate.
NOTE : Averaging is supported by the Programming Library.
The analog inputs can be configured in either single-ended or differential mode.
The pinouts for the mapping for input channels in differential mode are specified in Table 14-1: I/O Signal
Mapping .
For a single-ended input, the input voltage on the input pin is measured in comparison to the analog Ground
pin on the I/O connector.
NOTE : It is recommended
to
avoid using digital Ground pins for analog input measurements since it will
display a higher noise-level and result in less accurate readings.
In a differential input, the voltage measurement is the value between the high and low input channels.
NOTE : In differential mode, the A/D value will not yield a measurement lower than 0V, corresponding to
an A/D code of 0. In this scenario,
the inputs may be considered to be “pseudo-differential”. A
differential input is useful if the sensor or device being measured is far from the board or is
powered by a different power supply wherein the Grounds of the two systems may differ.
A more accurate measurement can be obtained by connecting the Ground of the device being
measured to the low channel on the SAM circuit, and the input signal to the high side.
The 12-bit resolution refers to the conversion of an analog voltage to a digital value in 12-bit integers.
The circuit can measure the input voltage with an accuracy of 3.3V / 4096 or approximately 0.81mV. The
conversion formulas between the input voltage and A/D code shown below, are based on the ideal case
scenario.
A/D Conversion Formulas:
A/D code = input voltage / 3.3V x 4096 (min value 0, max value 4095)
Input voltage = A/D code / 4096 x 3.3V