Applies To:
  • CitectSCADA x.x
Summary:
Question: What is the response time I should expect with my project? 

Solution:
The response time of a Citect Project depends on various factors.

1). The type of PLC protocol you are using to communicate between Citect and the PLC. The performance of PLC protocols vary greatly due the design an implementation of the protocol. This is not a limitation of Citect, but of the protocol and PLC design. The performance difference between the fastest and the slowest is great. The fastest PLC protocols are 100 times faster than the slowest. So if you are using a slow PLC protocol you will get very slow response time.

2). How well your Citect project is engineered will greatly impact on the performance. A a poorly engineered project could be 5 times or more slower than a well engineered system. A well engineered system has all the PLC data packed into easy to read blocks. The processing time of the alarms, trends and reports is set to not create big loads on the PLC. Cicode has been coded correctly to not cause excessive CPU or PLC loading. The I/O device cache time is set correctly.

Here is some typical examples of real Systems performance.

RESPONSE TAGS NODES PROTOCOL COMPUTERS COMMENTS
400ms 34,000 10 ABTCP Pentium 100Mz, 16M Win 95 New food production plant. Redundant Citect servers, 100Mb Ethernet between servers and 10Mb to clients.
800ms 12,000 1 LON using TCP/IP Gateway Pentium 100Mz, 16M Win 95 Building management, controlling HVAC for 42 story Building.
1600ms 38,000 45 CCM 486/66 8M, WfW 3.11 Ship loading facility. Upgrade of existing SCADA system using GE Series 6 PLCs. Performance is limited by slower 19.2k Baud serial links to 30 PLCs. Redundant Citect servers
2500ms 10,000 3 SYENET Pentium 100Mz, 32M Win 95 Water filtration plant.
400ms 15,000 10 ABTCP+ Yokogawa Pentium 100Mz, 32M Win NT ACID production plant to interface to new AB PLCs and existing Yokogawa hardware. Fully redundant with dual NT Citect servers, dual Ethernet to Citect clients and dual Ethernet to AB PLCs.
400ms 450,000 65 ABTCP Pentium Pro 200, 64Mb RAM, Win NT Clients, Servers same with 256 Mb RAM Upgrade and expansion of copper smelter. 12 Redundant Citect Servers, Dual 100Mb Switched Ethernet between servers and 10Mb to clients

The RESPONSE time is typical response time for a page update. As Citect uses dynamic optimisation the response time will vary depending on the page you are displaying and other background activity like alarms, trends and reports. This information can be found in the Citect kernel by displaying PAGE TABLE STATS. The following line 'Citect 0' show the statistics for the page (0) window. The average response time (show below as 0.265 seconds) is the best indication of response times.

Name (Cycle) Min Max Avg (exec) Min Max Avg Count
Citect 0 0.101 1.675 0.265 0.001 0.239 0.003 140

In version 5.20 this statistics included the page scan time and the [PAGE]AnmDelay delay time. This makes it difficult to see what the true PLC scan time. This problem has been fixed in version 5.21.

For full details on PAGE TABLE STATS see Q1890.

The TAGS is the total number of variable tags defined in the system. This includes DISK and Memory PLC tags, but does not include local cicode tags. If you have a single Project with no includes this is the number of records in the TAG database. If you have lots of includes the easily way to count the tags is to run Citect and display in the kernel PAGE RDB _VARIABL. Then press PgDn 10 times to display the table _VARIABL.Variabl. The following text will be displayed:

Table _VARIABL.Variabl
Handle 120 Length 000116 Offset 000000.000000 Base 00b3:ffffdd98

The Length (show here as 000116) is the number of tags in your project.

The NODES is the number of Citect nodes on the network including display nodes and Citect servers.

The PROTOCOL is the Citect protocol being used.

 
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