4.7. DataPid - a PID loop data simulation program


4.7. DataPid - a PID loop data simulation program
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DataPid is a data simulation program for the DataHub program. It simulates data for a set point, control output, and process variable, and sends these values to the DataHub instance by a TCP connection.


	This program is similar to DataSim, but with specialized data. A PID loop is often used by process control engineers to determine the efficiency of their system. A detailed explanation of PID loops is beyond the scope of this manual, but the data generated by this simulator can by used by anyone.

Starting Up

The DataPid can be started from the Windows Start menu, the command line, or by clicking on the desktop icon.

As soon as DataPid starts, it attempts to connect to a DataHub instance and begins generating data. To receive the data, the DataHub instance should configured up as a tunnelling/mirroring master.

The DataPid can take several command-line arguments at startup, to assist in running more than one instance at a time. Any combination of the following arguments can be supplied in the Target field of the shortcut, or on the command line.

/d data domain name: The name of the DataHub data domain in which to write the data that DataPid generates. The default is DataPid.
/n pid name: The name of the PID loop. For example, if data domain name is DataPid and pid name is PID1 then the data will the data will be created in a hierarchy beneath the point DataPid:PID1. The default is PID1.
/h host name: The name of the computer on which the DataHub instance is running. This can be an address or a name, for example, 127.0.0.1 or developers.cogentrts.com. The default is localhost.
/p port number: The port number on the target computer on which to connect. The default is 4502.
/i: If specified, the DataPid window will be iconified when it starts.

Example:

DataPid.exe /i /d test /n pid

Connection Parameters

Host: The name or IP address of the host computer. Since DataSim connects via TCP, this can be any computer on the network running a DataHub instance acting as a tunnelling/mirroring master.
Service: The port number or service name as entered in the Master service/port entry box of the DataHub instance.
Status: Displays the attempts to connect, which change to Connected when the connection is made.

You can use the Reconnect button to reconnect and the Pause button to freeze all data generation. Press the More... button to view and change some of the data parameters:

Configurable Options

The following options can be set in DataPid, and sent to the DataHub instance. All of the numeric options have a corresponding point in the DataHub instance that contains the value. Thus, these values can be set from within the Data Browser, by selecting the point name and entering a new value for it.

Setpoint (SP)

Manual	A number from `0` to `100` to for the set point. An entry here overrides Auto.
Auto	Changes the set point randomly, every `n` seconds, where `n` is the number entered.
Point	Changes the set point according to a point registered in the DataHub instance.

Controller (MV)

Kp	The proportional control factor, sets the speed of adjustment.	The wave form button sets a well-tuned PID loop.
Ki	The integral control factor, reduces error.	The wave form button sets a poorly-tuned PID loop.
Kd	The derivative control factor, provides a damping effect.	The wave form button sets an oscillating PID loop.

Plant (PV)

Kp	The proportional control factor of the plant.
Ki	The integral control factor of the plant.

Waveform Parameters

Amplitude	Not yet documented.
Offset	Not yet documented.

Data Domain

The DataHub data domain name for the data points. Any entry in this box changes the connection Status to IDLE. You must press the Reconnect button to reestablish the connection.

Update Frequency

The number of times per second that data changes and is sent to the DataHub instance.

Apply Changes

Applies any changes that have been entered for these configurable options. This button is greyed out until a change has been entered and can be applied.

Data Graph

SP, MV, and PV: The toggle button hides or shows the graph display. The numerical value is shown at the right of the graph.
Display Mode: Controls how the data is displayed in the trend display. Scroll moves the wave from right to left as the data is generated. Old data scrolls off the left side of the display as new data scrolls in from the right. Wrap adds to the wave from left to right, and writes over old data.

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