DAQ system operation

This page contains instructions for acquiring data via the tank's DAQ system. Before attempting to operate any systems, please read the general operating guidelines.

NI CompactDAQ chassis/modules

This section contains instructions for acquiring data from modules inside the NI 9188 CompactDAQ chassis in the DAQ cube.

9205: Analog voltage input

Signals from sensors on the order of volts (not mV) can be acquired via the NI 9205 module with 16-bit resolution. For pin connections, open Measurement and Automation Explorer, right click on the device (under "Network Devices"), and click "Device Pinouts".

How-to

1. Connect the sensor's leads to the appropriate spring terminals. Pairs for differential inputs are oriented horizontally. These terminals require a small flat-blade screwdriver to open.
2. Open National Instruments Measurement and Automation Explorer (NI-MAX) and look under Devices and Interfaces->Network Devices for the NI cDAQ 9188 chassis, under which you should find the appropriate module name. If there is a red X on the device icon, ensure the chassis is connected to the on-board "Ethernet 1" jack and click "Reset Chassis".
3. You can check that the device is measuring properly by opening "Test Panels" from the toolbar.
4. Set up your software application to acquire samples using the NI DAQmx driver. See software for more details.

9237: Bridge-based measurements

Signals from bridge-based sensors—strain gages, load cells, pressure transducers, etc.—can be acquired using the NI 9237 module. The module includes cables with RJ50 (10-pin) connectors and terminal blocks, which are stored in the plastic bins on the shelves. Note that when using the 9237 with other modules in the chassis, that the signals from the 9237 will have a small, but repeatable and predictable delay compared to the 9205 and 9401 due to the built in digital filters. See this article for details on how to calculate and compensate for this delay.

How-to

1. Connect the sensor's leads to the appropriate screw terminals on one of the terminal block adapters. See example pin connections in the table below.
2. Connect the terminal block adapter to the 9237 module with one of the black 10-pin RJ50 cables. Note: Do not use standard 8-pin Ethernet patch cables with this module and its terminal blocks.
3. Open National Instruments Measurement and Automation Explorer (NI-MAX) and look under Devices and Interfaces->Network Devices for the NI cDAQ 9188 chassis, under which you should find the appropriate module name. If there is a red X on the device icon, ensure the chassis is connected to the on-board "Ethernet 1" jack and click "Reset Chassis".
4. You can check that the device is measuring properly by opening "Test Panels" from the toolbar.
5. Set up your software application to acquire samples using the NI DAQmx driver. See software for more details. Note that due to the 9237's internal signal conditioning, sample rates should be (and are coerced to) 50000/n Hz, where n = 1...31.

Pin connections example: Sentran load cell

Signal	Wire color	Term. block pin
Excitation (+)	Red	6
Excitation (-)	Black	7
Signal (+)	Green	2
Signal (-)	White	3
Shield	Bare	S

9401: Digital input and output

The NI 9401 module is a TTL level digital I/O device with 100 ns resolution, capable of acquiring digital input and generating digital output. The devices 8 channels are configurable by nibble. More details can be found on National Instruments' website.

9411: Differential encoder input

This module's main purpose is to read from the tank's linear encoder using the carriage_pos global virtual channel.

Software

It is recommended that software be developed for each experiment. However, there is a LabVIEW VI Tow Tank DAQ that can perform basic DAQ tasks and serve as a foundation for new applications. Tow Tank DAQ.vi is designed to acquire voltage or bridge measurements from channels defined as DAQmx Global Virtual Channels. Global Virtual Channels are defined in NI's Measurement and Automation Explorer.

Ethernet-serial server

The 8 port Ethernet-serial server in the DAQ cube provides virtual COM ports for connecting serial devices on the carriage. To see which physical connector corresponds to which COM port, look in the Windows Device Manager (hint: Press the Windows key on the keyboard and type "device manager").

Connecting on the carriage

Note: The DAQ cube should now be connected by default. These steps are only necessary if it has been removed.

1. With an Ethernet patch cable, connect the NI 9188 chassis to the "Ethernet 1" jack on the on-board electronics cabinet, shown in Figure 1.
2. If using the Ethernet-serial server, connect the serial server to "Ethernet 2".
3. Plug the DAQ cube's power strip into one of the on-board 120 VAC outlets and turn the power strip on.
4. At the tow tank PC, open NI MAX and reset the NI 9188 chassis.