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Acquire Data from an OPC Historical Data Access Server

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This example shows you how to acquire data from an OPC Historical Data Access (HDA) server.

PREREQUISITES:

Start Historical Data Logging on the Server

NOTE:You do not normally need to execute this step on a production server.

This example uses a simulation server that only logs historical data for items that are subscribed using an OPC Data Access client. Load the client object from a MAT file and reconnect the client.

daObjs = load('opcdemoHDAConfigure.mat'); connect(daObjs.opcdemoHDAConfigure);

Wait a while for the server to log some data.

pause(10);

Create an OPC HDA Client Object

Create an OPC HDA Client associated with the OPC HDA Server.

hdaObj = opchda('localhost','matrikon.OPC.Simulation')
hdaObj = OPC HDA Client localhost/matrikon.OPC.Simulation: Host: localhost ServerID: matrikon.OPC.Simulation Timeout: 10 seconds Status: disconnected Aggregates: -- (client is disconnected) ItemAttributes: -- (client is disconnected)

The client object manages the connection with the server, allows you to retrieve information about the server, browse the server name space, and to read data stored on the server.

At this point, the client is not yet connected to the server. Connect the client to the server.

connect(hdaObj);

To confirm that the client is connected, display the clientStatusproperty.

hdaObj.Status
答= connected

Define Items of Interest

This example uses theReal8items fromSaw-toothed Wavesand theReal8andUInt2items fromRandom. Make a cell array of item names for ease-of-use.

itmIDs = {'Saw-toothed Waves.Real8',...'Random.Real8',...'Random.UInt2'};

Read Raw Data from the Server

Read the raw data values from the historical server over the past day.

data = readRaw(hdaObj,itmIDs,now-1,now)
data = 1×3 OPC数据对象:注重科技进步ItemID价值art TimeStamp End TimeStamp Quality ----------------------- --------------- ----------------------- ----------------------- ---------------------- Saw-toothed Waves.Real8 9 double values 2016-04-12 16:30:17.662 2016-04-12 16:30:25.776 1 unique quality [Raw] Random.Real8 9 double values 2016-04-12 16:30:17.662 2016-04-12 16:30:25.776 1 unique quality [Raw] Random.UInt2 9 uint16 values 2016-04-12 16:30:17.662 2016-04-12 16:30:25.776 1 unique quality [Raw] Use the showValues method to display all values.

Note:The Matrikon server retains only the last 200 simulated values for each item.

Display the values of the first data element.

showValues(data(1))
OPC HDA Data object for item Saw-toothed Waves.Real8: TIMESTAMP VALUE QUALITY ======================= ============= ========== 2016-04-12 16:30:17.662 3.141593 Raw (Good) 2016-04-12 16:30:18.677 6.283185 Raw (Good) 2016-04-12 16:30:19.692 9.424778 Raw (Good) 2016-04-12 16:30:20.707 12.566371 Raw (Good) 2016-04-12 16:30:21.717 15.707963 Raw (Good) 2016-04-12 16:30:22.732 18.849556 Raw (Good) 2016-04-12 16:30:23.747 21.991149 Raw (Good) 2016-04-12 16:30:24.761 25.132741 Raw (Good) 2016-04-12 16:30:25.776 28.274334 Raw (Good)

Read Processed Data from the Server

Query theAggregatesproperty of the HDA Client object to find out what aggregate types the server supports.

hdaObj.Aggregates
答= OPC HDA Aggregate Types: Name ID Description ----------------- -- ------------------------------------------------------------------------------------------- INTERPOLATIVE 1 Retrieve interpolated values. TIMEAVERAGE 4 Retrieve the time weighted average data over the resample interval. MINIMUMACTUALTIME 7 Retrieve the minimum value in the resample interval and the timestamp of the minimum value. MINIMUM 8 Retrieve the minimum value in the resample interval. MAXIMUMACTUALTIME 9 Retrieve the maximum value in the resample interval and the timestamp of the maximum value. MAXIMUM 10 Retrieve the maximum value in the resample interval.

The Matrikon server supports the time weighted average value, so we will use that aggregate type on 10 seconds of data for the last 1 minute. Note below how theAggregatesproperty can be used to specify the aggregate type.

pData = readProcessed(hdaObj,itmIDs,hdaObj.Aggregates.TIMEAVERAGE,10,now-1/24/60,now)'
pData = 1-by-3 OPC HDA Data object: ItemID Value Start TimeStamp End TimeStamp Quality ----------------------- --------------- ----------------------- ----------------------- ----------------------------- Saw-toothed Waves.Real8 6 double values 2016-04-12 16:29:26.840 2016-04-12 16:30:16.840 1 unique quality [Calculated] Random.Real8 6 double values 2016-04-12 16:29:26.840 2016-04-12 16:30:16.840 1 unique quality [Calculated] Random.UInt2 6 uint16 values 2016-04-12 16:29:26.840 2016-04-12 16:30:16.840 1 unique quality [Calculated] Use the showValues method to display all values.

Display the values for theRandom.Real8item.

itmInd = getIndexFromID(pData,'Random.Real8'); showValues(pData(itmInd))
OPC HDA Data object for item Random.Real8: TIMESTAMP VALUE QUALITY ======================= ============= ====================== 2016-04-12 16:29:26.840 5073.986117 Calculated (Uncertain) 2016-04-12 16:29:36.840 5073.986074 Calculated (Uncertain) 2016-04-12 16:29:46.840 5073.986105 Calculated (Uncertain) 2016-04-12 16:29:56.840 5073.986137 Calculated (Uncertain) 2016-04-12 16:30:06.840 5073.986227 Calculated (Uncertain) 2016-04-12 16:30:16.840 7322.794889 Calculated (Uncertain)

The last value has a quality of'Uncertain'because the time interval is not a complete 10 seconds.

Clean Up

When you have finished with the OPC Toolbox™ objects, delete them from the OPC Toolbox engine. Although deleting an HDA Client object automatically disconnects the object from the server, this example explicitly shows it.

disconnect(hdaObj) delete(hdaObj) disconnect(daObjs.opcdemoHDAConfigure); delete(daObjs.opcdemoHDAConfigure);

The client object is now invalid.

isvalid (hdaObj)
答= 0

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