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Isolated/Stackable DAQ Module HMI SCADA Software
 

Isolated Stackable DAQ
Modules with Free Software

  • Digital Inputs
  • Dry Contact Inputs
  • Counter Inputs
  • Quadrature Encoder Inputs
  • Tachometer Inputs
  • Digital Outputs
  • Timer Outputs
  • PWM Outputs
  • Relay/Solenoid Control
  • Analog Inputs
  • Analog Outputs
  • Thermocouple Inputs
We offer a full line of low-cost Data Acquisition and Control modules which can be daisy chained together and connected to a single communications port of a PC or Laptop. Our HMI Software as pictured above is specifically designed to communicate with these modules and can be set up very quickly and easily by the novice with little or no programming skills. Advanced programmers can utilize the power of this software by writing complex scripts, conditional statements, and control logic that will run in the background.
 

Velocity Measurement Modules

WTPCT-M Pulse Counter/Timer Card WTPCT-M
Measures the precise time between two trigger inputs using 1ÁS resolution. The trigger source can be a trip wire or optical beam and the measured results can be used to calculate the velocity of a projectile. read more...

 

Measuring Velocity

To measure the speed or velocity of a projectile, a precision timer can be used to measure the exact time it takes for that projectile to travel a fixed distance. The DAQ module shown above incorporates a timer with a 1ÁS resolution and two trigger inputs to start and stop the timer. These trigger inputs can be attached to simple trip wires, or optical beam detectors, which are placed at a known distance from each other. As the projectile passes across these two trigger points, the exact time is recorded and returned to the host PC. The velocity can then be calculated using the "distance" and "time" data.

Stackable Capability

Stackable refers to the ability to connect multiple units together and share a single communications port of a host PC, laptop, or Single Board Computer (SBC). The communications bus uses a stratagem based on the Carrier Sense Multiple Access (CSMA/CD) protocol. Carrier Sense (CS) is the monitoring of the data bus for a period of inactivity before a DAQ module is allowed to begin its own transmission. Multiple Access (MA) means that once the bus is free, every DAQ module in the network has an equal opportunity to transmit a frame. And Collision Detection (CD) uses non destructive bit wise arbitration to preserve the integrity of a data frame when two or more DAQ modules try to transmit at the exact same time. And since the data frame that wins arbitration remains intact during a collision, there is no additional communications delay when a collision occurs no matter how often it happens.

Host Communications

To communicate with the DAQ modules, commands are sent to the individual units by including a header character at the beginning (the address) so that it can be routed to the appropriate unit. If using multiple units connected together, the DIP switch for each unit should be set to a different position so that it will be assigned a different header character. Each DAQ module has its own command set used to configure it, operate the functions, and to read data from it. These commands are listed in the product data sheets. A typical command string looks like this:

HCNV{cr}

H = Header Character
C = Command Character
N = Channel Number (if applicable)
V = Value (if applicable)
{cr} = Carriage Return

If using our ModCom HMI software, the carriage return is not necessary because ModCom automatically inserts this at the end of each command string. ModCom has a communications dialog box which can be used to transmit individual commands to the DAQ modules and see the data coming back. This is helpful in learning the style of the command-set protocol and testing the hardware that's attached to the DAQ module. It is highly recommended that this testing be done prior to setting up any complex control programs.