X90 mobile modules
248
X90 mobile system User's manual V 1.20 - Translation of the original manual
Quantization
To process analog signals digitally, an analog-to-digital converter (AD converter) is required. However, only volt-
ages in steps can be measured by an A/D converter. This is known as quantum voltage. The range to be measured
is thus quantized.
In an AD converter, the digital resolution depicts the number of levels there are in the quantization. This determines
the accuracy and sensitivity with which a previously analog level value is depicted. The more available levels there
are, the more precise the discrete signal received and the higher the sensitivity of the measurement.
The resolution indicates how many varying digital values an analog signal can be converted into. The resolution
is expressed in bits.
8-bit resolution
256 level values
16-bit resolution
65,536 level values
24-bit resolution
16,777,216 level values
Example
A 24-bit resolution, a sensor measurement range of ±10 V and a sensor sensitivity of 100 mV/g result in:
20V / 2
24
= 1.192 µV → Corresponds to 11.92 µg
Time
Sampling
0
1
2
3
4
5
-1
-2
-3
-4
-5
-6
Gauge
reading
Figure 80: Quantization error at low resolution
Information:
The module has 24-bit resolution.
Duration of measurement
The duration of measurement depends on the configured maximum frequency. Depending on whether the envelope
or raw values are to be measured, the following registers are used for configuration:
•
"MaxFrequencyEnvelope" on page 185
for envelope measurement
•
"MaxFrequencyRaw" on page 186
for raw value measurement
Maximum frequency
Sampling frequency
Duration of measurement
10000 Hz
25781 Hz
0.3178 s
5000 Hz
12891 Hz
0.6355 s
2000 Hz
5156 Hz
1.5888 s
1000 Hz
2578 Hz
3.1775 s
500 Hz
1289 Hz
6.3550 s
200 Hz
516 Hz
15.8875 s
