Company Events Academic Community Support Solutions Products & Services Contact NI MyNI

Glossary (DSC Module)

LabVIEW 2013 Datalogging and Supervisory Control Module Help

Edition Date: June 2013

Part Number: 371618J-01

»View Product Info
Download Help (Windows Only)

A

ACK (Acknowledge) The sequence action that indicates recognition of a new alarm.
alarm An abnormal process condition. In the LabVIEW Datalogging and Supervisory Control (DSC) Module, an alarm occurs if a shared variable value goes out of its defined alarm limits or if a shared variable has bad status.
alarm summary A display of shared variables currently in alarm, or a display of shared variables previously in an unacknowledged alarm state that have returned to a normal state.
Assignable Cause A cause that can be detected and identified as contributing to process variation.
Attribute Data Data from counting process results such as number of units non-conforming per inspected sample, or number of defects per inspected sample containing n units. As opposed to measured data, attribute data has a discrete number of possible values. p, np, u and c control charts are used to track attribute data.
Attributes Chart A control chart that tracks whether a process is in control by tracking attribute data, or data counted from the process. p, np, u, c charts are attributes charts.

B

bad status An indication that the value associated with a shared variable is invalid. A bad status might occur for several of reasons, for example, a hardware read error occurred.
batch process A process or production run that results in a batch of logged data, also known as a data set.

C

c Chart Control chart that uses number of defects per sample to monitor the stability of the process. Each sample contains n units, and contains c defects per sample (zero or more defects per unit). The value of n must be constant from sample to sample.
center line A line on a control chart representing average long-term value of the statistic plotted on the control chart.
Citadel A database for storing historical shared variable values.
control chart A charting method for determining the stability of a process; that is, whether or not a process is in a state of statistical control. Shewart control charts monitor process stability by plotting sample statistics against a center line and control limits.
control limits Upper and lower limits on a control chart represent the amount of variation about a center line that can be attributed to chance causes for a given process characteristic. Control chart points that fall outside the control limits signal that the process is not in control and that some action should be taken. Control limits may be calculated from process data or from standard values.
Cp process capability index A measure in sigma units of the process capability that is a ratio of the spread between the specification limits over the m sigma spread of the process variation, where m normally is 6.
Cpk centered capability ratio A measure in sigma units of the process capability with respect to how well the process is centered relative to the specification limits, also known as distance to nearest specification.

D

data item A channel or variable in a real-world device that is monitored or controlled by a device server.
data set A group of shared variable values logged together as a set during a specified period of time.
DataSocket DataSocket is both a technology and a group of tools that facilitates the exchange of data and information between an application and a number of different data sources and targets. It provides one common API to a number of different communication protocols.
defect A measured characteristic of a specific unit of product or service that prevents the unit from meeting a specification requirement or is otherwise undesirable. In a unit, one or more defects are possible, and many different types of defects are possible. A defect is also known as a non-conformity if the characteristic prevents the unit from meeting a specification requirement.
device server An application that communicates with and manages a peripheral hardware device such as a programmable logic controller (PLC), remote I/O device or plug-in device. Device servers pass shared variable values to the Shared Variable Engine in real time.
DSC Datalogging and Supervisory Control

E

engine See Shared Variable Engine.
EPICS Experimental Physics and Industrial Control System. A set of open-source software tools you can use to develop large, distributed control systems. EPICS also refers to the architecture of such systems, as well as to the collaboration group developing the related tools. Refer to the Argonne National Laboratory Web site at www.aps.anl.gov/epics for more information about EPICS and to download the latest version of EPICS.

F

fraction non-conforming The number of units in a sample not conforming to specification divided by the total number of units in the sample.

H

Histogram A graphical summary of data in which the individual values are sorted by the range of values into which they fall (also known as bins), and in which the number of individuals falling within a each bin is counted. The data is plotted by showing the number of values (frequency) in each bin.
historical trend A plot of data (values versus time) showing values that were previously acquired in the system or logged to disk.
Human Machine Interface (HMI) A graphical user interface for the user to interact with the DSC Module application.

I

ID shared variable (data set) When logging data sets, the ID shared variable for each data set denotes a particular data set and the time during which the data set run took place.
in-control process A stable process whose variation is due only to chance causes; that is, no assignable causes of variation are present.
individual observation A single measurement of a process characteristic.
input/output (I/O) group A set of related server items, all of which share the same server update rate and deadband.

L

LabVIEW Datalogging and Supervisory Control Module Run-Time System An execution environment for applications created using the DSC Module development system. Refer to the National Instruments Web site for information about the DSC Module Run-Time System.
logging deadband The range through which a shared variable value must change before the Shared Variable Engine logs it to a historical database.
logging resolution The smallest change in a shared variable value stored in the database.
Logos A proprietary National Instruments networking protocol, installed on the computer when you install the DSC Module.

M

measurement data Data that is a result of observations or measurements of a characteristic that has a continuous range. As opposed to attribute data, measurement data is not discrete. Any discreteness in measurement data is due to the resolution of the measuring device, not the characteristic.
Modbus An application-level messaging protocol that provides client-server communication between devices connected on different types of buses or networks.
moving Average chart Control chart that uses the average of n successive individual observations from a process to track the stability of the process mean. This type of control chart is typically used when the sample size is 1.
moving Range chart Control chart that uses the range between n successive individual observations from a process to track the stability of the process variation. This type of control chart is typically used when sample size is 1.

N

natural process limits The limits which contain a stated fraction of the individual observations in a population. For a normally distributed population, the stated fraction is typically the process mean ± 3.0 sigma.
non-conforming unit A unit of product or service that does not meet a specification requirement.
normally distributed If a process is normally distributed, expected values for individuals within the process population fall on a normal or bell-shaped curve.
np chart Control chart that uses the number of non-conforming units in a sample to monitor the stability of the process. The sample contains n units, and zero or more units may be non-conforming. The value n can be constant from sample to sample.

O

observation A measurement of a process characteristic.
ODBC Open Database Connectivity. A standard developed by Microsoft, it defines the mechanisms for accessing data residing in database management systems.

P

p chart Control chart that uses the fraction of non-conforming units in a sample to monitor the stability of the process. The sample contains n units, and zero or more units may be non-conforming. The value n can vary from sample to sample.
Pareto chart A chart of a set of counted or totalized characteristics in which the characteristics are ranked in order of their frequency of occurrence. In statistical process control, Pareto charts are normally used to evaluate relative contribution of assignable causes and prioritize corrective action.
process Project libraries that LabVIEW deploys to the Shared Variable Engine (SVE) are called processes. Making changes to a process or to a shared variable within a process without affecting the corresponding library is known as online configuration. Making changes to a library or to a shared variable in a library without affecting the corresponding process is offline configuration. If you use offline configuration to change a shared variable, you must redeploy the library to the SVE before you run any VI within the library so the SVE can update the shared variable in the process.
process capability A measure of the ability of a process to produce product within specification, assuming the process is stable. Specifically the variability that can be expected for a given process characteristic with respect to the specification limits for the characteristic.
proxy user You can specify a proxy user account as a way to handle unrecognized access requests for data.

R

R (Range) chart Control chart that uses the sample range R to track the stability of the variation in the process. Sample range is max sample value minus min sample value. Sample size must be 2 or more.
real-time trend A plot of data (values versus time) that is updated as each new point is acquired in the Shared Variable Engine.
run chart A chart of the individual observations in a set of samples plotted in time order of occurrence.
run rules Rules applied to a consecutive set of points on a control chart, that are used to detect changes in the process such as out-of-control conditions, or process shift.

S

s (std dev) chart Control chart that uses the sample standard deviation s to determine the stability of variation in the process. Sample size must be two or more.
sample A set of measurements (observations) or units (from which counted data is taken) used as a basis for evaluating the process.
sample (or subgroup) size For measurement data, this is the number of observations (or individual measurements) making up the sample. For attribute data, this is the number of units n inspected for the counted characteristic.
shared variable attributes Parameters pertaining to a shared variable, including its alarm, limits, or engineering units. Configure shared variable attributes in the Shared Variable Properties dialog box.
Shared Variable Engine The software service that maintains all shared variable values and alarm states and runs as a separate process, independent of the HMI application.
shared variable group A set of shared variables primarily used for reporting and acknowledging alarms. A shared variable can be associated with only one shared variable group. All shared variables belong to the group <ALL> by default.
shared variable status A shared variable attribute that determines the validity of a shared variable value. A negative status represents an error, a positive status represents a warning, and a status of zero represents a good shared variable value.
specification limits Limits that define the range within which a product or characteristic conforms to specification or user requirements (also known as tolerance limits).
SQL Structured Query Language
standard values The known standard values for process range, sample standard deviation, mean, or sigma from which control limits can be calculated.
subgroup A set of measurements (observations) taken from a larger set.
system errors Errors that happen in the DSC Module Run-Time System, like a server going down. LabVIEW displays system errors a dialog box.
system events Events that occur in the DSC Module Run-Time System, like an operator logging on or a utility starting.

T

tier chart A chart in which the individual observations in each sample are plotted vertically. It is a useful means of visualizing the variation or spread in each sample.
timestamp The exact time and date at which a shared variable value was sampled. Shared variable values are stored with their time stamps in the Shared Variable Engine.
trace Shared variable data that logs to the database. A trace contains the data type, data values, timestamps, and qualities of the shared variable.
trend A view of data over time. Trends can display real-time or historical data.

U

u chart Control chart that uses the average number of defects per sample to monitor the stability of the process. The sample contains n units, and contains c defects per sample (zero or more defects per unit). The value n may vary from sample to sample.
update deadband The range through which a shared variable value must change before it updates in the Shared Variable Engine.

V

variables chart A pair of control charts that track whether a process is in control by tracking mean and variability of samples of measured data. Variables charts include X-bar & s, X-bar & R, x & mR charts, and mX-bar & mR charts.

X

x (individual) chart Control chart that uses the individual observations from a process to track the stability of the process mean. This type of control chart is typically used when sample size is 1.
X-bar chart Control chart that uses the sample mean, X-bar, to track the stability of the process mean. Sample size must be 2 or more.

 

Your Feedback! poor Poor  |  Excellent excellent   Yes No
 Document Quality? 
 Answered Your Question? 
Add Comments 1 2 3 4 5 submit