AVL F-FEM-CON User Manual

39
Operation
F-FEM-CON — User’s Guide
4.1.3 AC Characteristics
4.1.3.1 Requirements
In order to reach the specified sampling accuracy, it is absolutely necessary to
observe all of the instructions on shielding and system wiring found in the
chapter Installation on page 21. Only then will the signals be delivered to the
F-FEM-CON with the required quality.
4.1.3.2 Signal Noise Ratio (SNR)
with
N = log
2
(5000)
SNR = -140 dBFS + 3 dBFS * log
2
(5000) – 1) = -106 dBFS
This value corresponds to a resolution of 17.6 bits.
4.1.3.3 Total Harmonic Distorsion (THD)
A THD value of 0.005 % (50 ppm) resulted for the measurement with 16.6 cycles
per second.
For the measurement with 99.8 cycles per second this value amounted to only
0.0042 % (42 ppm).
These values were determined using a frequency generator whose max. THD
was above the measured values. Thus, they have to be regarded as the upper
boundary.
4.1.3.4 Notes
 A 5000 points DFT is used.
 For coherent measurement, the input frequency is selected as follows:
1000 Hz / 5000 * 83 = 16.6 Hz or
1000 Hz / 5000 * 499 = 99.8 Hz
Whereby 1000 cycles per second / 5000 correspond to the lowest coherent
sampling rate. 83 and 499 are prime numbers.
 Function generator and F-FEM-CON have been synchronized.
 All values refer to the full scale value of the ADC (±27 V). Size of dominant
mode: 20 * log
10
(10V/27V) = -8.63 dBFS.
Sampling rate 1 kHz
Input signal Sine, +
2.5 V, 16.6 Hz
Sine, +
10 V, 99.8 Hz
DFT 5000 points
SNR = Noise Floor (dBFS) + 3 dB * (N-1)

AVL F-FEM-CON Specifications

General

Brand	AVL
Model	F-FEM-CON
Category	Measuring Instruments
Language	English