Pickering 41-670 - Input Signal Gain Adjustment

SECTION 4 - PROGRAMMING GUIDE
Page 4.5
PXI/PXIe LVDT/RVDT/Resolver Simulator Module 41/43-670
pickering
Input Gain
NOTE: It is very important that the input gain is set to the optimum level. This is for the signal to be internally
scaled correctly for maximum sampling resolution.
Choose the correct version of LVDT simulator module to cover the desired input and output levels and excitation
frequency, these specication limits are dened by hardware parameters. The excitation input needs to be scaled to
an optimum level for sampling without clipping, the scaling of the sampled excitation input is independent from the
output level.
If the input level is applied within the module’s limits the Automatic gain function can adjust the input level to 95% of
maximum, when the Vsum function is used to set the output, the input level is value is used to automatically compute
the required output levels.
If the auto input gain value is set at 255, the gain adjustment is at maximum and it is likely that the input signal is
too small. Likewise, if the returned input level reads at either limits; 32768 (signal too small) or 65535 (too large
clipping likely), the sampled input will be degraded. The ideal signal level value will be approximately (65535 * 95%
= 62,258). Lower values of input level will give reduced sampling resolution.
After the gain has automatically been set to optimum, setting the Vsum function uses the current input level value to
calculate the required output level.
Input
Attenuation
Stage
Sampling
ADC
Figure 4.4 - Input Gain Incorrectly Set
Figure 4.4 - Input Gain Set to Optimum Level