DAQ Board and Modules

Transcription

1 DAQ Board and Modules Data Acquisition (DAQ) boards are the way computers communicate with sensors and actuators to interact with the external world. Every DAQ board has usually the following capabilities: Digital Input/Output (DIO), Analog Input (AI), Analog Output (AO). Several Labs will be dedicated to learning those capabilities. On one end, DAQs are usually connected to the computer s motherboard via PCI (for Desktops), or PCMCIA (for Laptops). USB, Ethernet, IEEE1394 (Firewire), or other types of buses are sometimes used as well. This connection is used for the DAQ to talk with the microprocessor and, ultimately with the application that the user is running (e.g. Matlab, LabView, ). On the other end, DAQs are usually connected with Module Racks, Modules, Terminals and dedicated Printed Circuit Boards (PCBs) that are used to efficiently route the sensors wiring to the Board s Analog or Digital Inputs and to route the Board s Analog and Digital Outputs to Servos and Actuators. PCI-DAS6025 BOARD: The following picture shows the DAS6025 Board. Figure 1: Data Acquisition Board PCI-DAS6025

2 The first page of the manual says: The PCI-DAS6025 provides 16 channels of 12-bit analog input, with a 10 ks/s per channel update rate. The inputs can be configured as either eight differential or 16 single-ended, with software selectable ranges of ±10 V, ±5 V, ±500 mv, and ±50 mv. There are 12-bit analog outputs, 32 digital I/O lines and two 16-bit counter timers. Connection Cable: The DAQ board is connected with a cable called C100HD50-x, which routes the 100 Board pins to the rack and the modules on your project board: Figure 2: Connection Cable SSR-24 Module Rack and Relays: Look at your Project Board and find the SSR-24 rack:

3 Figure 3: SSR-RACK24 The SSR-RACK24 is a mounting and interface rack to mount standard size solidstate relays (SSR stands in fact for Solid State Relays) like the one in the following Figure: Figure 4: Solid State Relay Keep in mind that the SSR-RACK24 is connected to the digital output part of the DAQ board. Note that the rack needs a +5V voltage source, which is externally supplied by the power supply. Also note that there are already several screw terminals that allow you to connect easily to the rack without touching it. CIO-MINI50 Module: Look at your Project Board and find the CIO-MINI50 modules. There are two CIO-MINI50 modules mounted on the bigger (SSR-24) Rack.

4 Figure 5: CIO-MINI50 Module The CIO-MINI50 on the right side of the project board is connected to the Analog input and Output section of the DAQ board, and is used to provide analog outputs (2 channels) and acquire analog inputs (8 channels). Remember that an analog output is a voltage between two wires, provided by the DAQ board. This is a voltage that can assume any value within a certain range, in this case between -10 and +10 volts. To be more correct, the output can assume 2^12 = 4096 different values within the ±10V range. The maximum frequency for the generated output signal is 10 KHz. An analog input is a voltage between two wires that can be acquired by the DAQ board. Again, analog means that it is a voltage that can assume any value within a certain range, which can be selectable. The Input Resolution of the board is 12 bits, meaning that the output can assume 2^12 = 4096 different values within the selected range. The CIO-MINI50 on the left side of the project board is connected to the Digital Input and Output section of the DAQ board, and is used to provide digital outputs and acquire digital inputs. There are 8 channels, independently programmable for input or output. The digital outputs are connected to the relays in the SSR24 rack. Note that a digital output channel is a voltage between two wires, provided by the DAQ board. Digital means that it is a voltage that can assume only 2 values, either low or high, in this case these values are respectively less than 0.55V and greater than 3.80V. A digital input channel is a voltage between two wires, which can be acquired by the DAQ board. Again, this voltage is either low or high. Any voltage lower

5 than 0.5V is considered low while any voltage greater than 2V is considered high. Screw terminals: Analog inputs and analog outputs, digital inputs, digital outputs, are already attached to screw terminals on the project board, that way, you don t need to mess around directly with the rack and modules, and you don t need to figure out every time which input or output you have to connect to. Instead, the only thing you need to do is connect the wires to the appropriate screw terminal. Project Board: This is the typical project board: Figure 6: Project Board Analog I/O Terminals Power Supply Terminals Relays (Digital output) Terminals Digital Inputs Terminals