Greetings-
I'm using the following software / hardware:
LabVIEW 6.1
PCI-MIO-16XE-50
SCXI-1000 chassis
SCXI-1520 Strain Gauge Conditioner
1314 Connector Block
NI-Daq 7.2.0f1
Transducer Techniques full bridge absolute load cell, 10VDC excitation
I'm using the "Getting Started with Load Cells" VI and have some questions about the functionality of this VI and the SCXI-1520 hardware. I've searched every piece of documentation I can find regarding the nulling features of the 1520 yet am still confused.
I have found two pieces of conflicting information regarding whether or not I need to manually connect my S+ and S- signals to chassis ground when performing a Null. According to "How Can I Measure a Full-Bridge Absolute Transducer with the SCXI-1520" document, using Traditional NI-Daq, Step 5 explains that S+ and S- signals should be shorted to chassis ground.
Yet, on the block diagram of the VI "Determine Offset and Null" it appears that the S+ and S- channels are programmatically shorted to ground through the use of CalGnd channels. Is this functionality the same for both Traditional Daq and DAQmx? Do I need to manually short my S+ and S- signals to ground?
Additionally, each time I perform a null on a specified channel, the residual offset voltage value is always larger than the initial voltage offset. The initial voltage offset is on the order of micro-volts while the residual offset voltage is on the order of milli-volts. Shouldn't the residual offset be much smaller than the initial offset?
Regarding the Gain setting:
According to the 1520 User Manual, "configure gain using module properties. When you set the minimum and maximum range of the virtual channel, the driver selects the best gain". So which gain is used? Is it the module gain settings or that selected as a result of the Virtual Channel creation? Which value takes precedence?
I have verified that my 1520 is configured correctly with the 1314 accessory and set to full bridge with a non-zero excitation voltage of 10VDC.
I've created the input channel using MAX as an Analog Voltage input using the Map Ranges functionality to translate the milli-volt output of the sensor to load (lbf)
Thank you in advance for any suggestions.
