MODELS 483C30, 483C50, 482M179 AND 483M217 GENERAL OPERATION MANUAL
5
2-3.
Input Fault Detection
These models monitor two input fault conditions; “short” and “open,” which indicate problems with sensor input and is
displayed through the front panel LEDs. Either case implies that the sensor is NOT functioning properly. An input is
shorted when it has a ground path for the sensor excitation and open when the sensor fails to draw the excitation.
Two voltage comparators consist of a window comparator that has two reference voltages (V
ref
) representing thresholds
for “short” and “open.” When the sensor’s bias voltage (V
bias
) exceeds the comparator range, the front panel input fault
LED lights.
NOTE: Red LED implies input fault.
Figure 3 Input Fault Window Comparator with LED Indicator
2-4.
Input Interface
The input signal conditioning for each channel provides a unity gain buffer with high-input impedance amplifiers. With
the AC coupled option it also eliminates the DC bias from the input signal with a 10-second time constant.
Figure 4 Input Amplifier Configuration
2-5.
Gain
The Programmable Gain Amplification (PGA) block consists of a decimal gain amplifier. See Figure 5.
Figure 5 Selectable Gain Amplifier Configuration