Appendix B. SIO
Configuration
Doc.#6000-0015 Rev: A
Page 49
The screen in Figure B5 is for bridge sensor signal conditioning. Note that
it will add an ADC readout value. The bridge circuit has three
programmable parameters:
•
PreGain Null: This is used to zero the voltage differential from the
bridge outputs into the SIO’s amplifier circuit.
•
Programmable Gain: Controls the gain of the SIO amplifier.
•
PostGain Null: Sets the output level of the amplifier.
Three control buttons (plus EXIT) are available:
1. CONFIGURE: Loads the selected PreGain Null, Gain, and Post
Gain Null into the SIO but doesn’t store them into the SIO’s flash
memory.
2. PROGRAM: Stores the selected values into the SIO’s flash
memory.
3. RESTORE DEFAULT: Restores the old SIO values stored in flash
memory.
The output from the bridge sensor must be balanced. Before proceeding,
the sensor’s sensitivity and the system’s ideal gain need to be determined.
1. Determine the bridge sensor sensitivity in Volts/EU as follows:
Sensitivity = Full Scale Voltage Output/Full Scale EU
As an example, for a 300 lbs load sensor with a 3 mV output per
volt excitation at full scale and a SIO providing 5 V excitation, the
sensitivity would be:
Full Scale Output = 3 mV * 5 V Excitation * 0.001 V/mV
= 0.015 V
Sensitivity = (0.015 V)/(300 lbs) = 5E-5 V/lbs
2. Determine the ideal gain for the SIO-sensor as follows:
Ideal Gain = SIO Output Voltage Range/Sensor Full Scale Output
Assume the example sensor is a compression cell with a small
tension overshoot; then the desired Node voltage gain could be
chosen as 4 V with 1 V being zero load. The ideal gain would be:
Ideal Gain = 4 V SIO Volt Range/0.015 V Sensor FSO = 266
To balance the bridge:
1. Connect to the Node and SIO. Use the “SIO Configurator” main
window, Figure B1, “Read SIO” command on the SIO dropdown
menu to read in the SIO information.
2. Set the Calibration Gain for the sensor.
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