Chapter 3
Configuring Your SCXI Hardware and Software
©
National Instruments Corporation
3-35
You can use direct function calls to NI-DAQ to configure and calibrate the
SCXI-1520 as well as scale data acquired through the SCXI-1520.
Table 3-27 lists these functions and describes their use.
The SCXI-1314 terminal block provides a convenient method of
connecting field wiring from strain gauges and strain-gauge based sensors
to the front signal connector of the SCXI-1520. The terminal block
includes a socketed quarter-bridge completion resistor and two socketed
shunt calibration resistors for each channel.
SCXI-1530/1531 Module
The SCXI-1530 and SCXI-1531 are four- and eight-channel modules,
respectively, used for interfacing with Integrated Circuit Piezoelectric
(ICP
®
) and other current-excited accelerometers. They have BNC
connectors for direct connection to accelerometer cables. You can turn
the 4 mA current excitation on or off. You can set the bandwidth of the
four-pole Bessel filter to 2.5, 5, 10, or 20 kHz. You can set the gain to 1,
10, or 100X. All channels are simultaneously sampled and held to preserve
timing and phase information. Excitation, bandwidth, and gain are set
Table 3-27.
NI-DAQ Functions Applicable to the SCXI-1520
Function
Action
SCXI_Set_Gain
Sets the analog input gain within the allowable range of
X1 to X1000.
SCXI_Set_Excitation
Sets bridge excitation voltage. Range is from 0 to 10 V
in 0.625 V steps.
SCXI_Configure_Filter
Sets filter cutoff frequency to one of five settings:
10 Hz, 100 Hz, 1 kHz, 10 kHz, or bypass.
SCXI_Strain_Null
Automatically zero-nulls the sensor-induced offset
voltage of the specified channel.
SCXI_Calibrate_Setup
Enables or disables shunt calibration on a per channel
basis.
SCXI_Configure_Connection
Sets the bridge configuration to quarter, half, or full
bridge.
SCXI_Calibrate
Initiates a module self-calibration. Updates the gain and
offset constants stored in the EEPROM of the module.
These constants are used by the scaling function
SCXI_Scale
.
