MULTICHANNEL SIGNAL CONDITIONER MODEL 482C27 GENERAL OPERATION MANUAL
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3-2.
Input Protection
The input section has protection to limit the amplitude of the incoming signal to 24 volts to ground. Maximum
allowable input voltage without distortion is ±10 volts, relative to the sensor bias voltage.
3-3.
Input Fault Detection
Model 482C27 monitors 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 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
3-4.
Input Interface
The input signal conditioning for each channel provides a unity gain buffer with high-input impedance amplifiers. AC
coupling eliminates the DC bias from the input signal unless DC coupling is enabled.
Figure 4 Input Amplifier Configuration
3-5.
Normalized Output Sensitivity
The definition of normalized output sensitivity is the calculation of the individual channel’s gain, depending on the
sensitivity of the sensor attached and the desired output sensitivity. This is simply a function of the desired output
sensitivity (in Volts/ unit) divided by the sensor’s sensitivity.
Gain =
1 Volt
/
Sensitivity (mV/unit)
Additionally, a feature to improve flexibility allows changing the output level to a value of 5 Volts/ unit instead of
normalized 1 Volt/ unit. Some users request the ability calculate the gain using a known input signal along with the
sensor sensitivity, and desired output level. The result of the request impacts the formula:
