We are reading 4 external counting signal and 1 internal 32 Khz clock simultaneously, via a FP-CTR-500 and a VisualBasic app

[Puho]

lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?The timing of reading from the VisualBasic application is 2 seconds, and external pulses are incoming at 8 Khz aprox.

[Aaron_G]

lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?The answer to your question depends upon several conditions. First, what network module is being used?
If an FP-1000 is being used, with the limitations of the OPC server not supporting items that have multiple analog (count) channels, we can not guarentee the synchronicity of the data. Using the Optomux Commands from the FP-1000/1001 Programmers Reference Manual, http://www.ni.com/pdf/manuals/321632c.pdf , you can use the !F or !G command to read the multiple channels at the same time to achieve the accuracy listed below.

If an FP-1600/2000/2010 is being used, they will normally do a scan of a all channels on a module at a time, then proceed to the next module. As long at the network module is attempting to read multiple channels in a single shot, the data f
rom the FP-CTR-500 will be a relatively synchronized reading (worst case between all channels should be approximately 18 microseconds).

Regards,
Aaron

[Puho]

lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?Dear Aaron,
An FP-1600 is being used in this system. I think that 18 usec is a relative short time for aour process, and it is lower than 1 cycle (100 usec) at full scale (10 KHz). Nevertheless, the application displays differences between readings greather than those we are expecting. The application reads the channel 0 and 1 (Counters at internal clock of 32 Khz), and calculates the elapsed time by substracting the last value. Simultaneously, the 4 external count channels are read (we think at the same time or with a difference of 18 usec in the worst case). After that, we calculate the "Events by second" (or frequency) of each external channel, in reference to the time elapsed in channel 0 and 1. Question: It is possible that OPC server returns more than 1 r
eading to the same request from the application?. It might be justifying the different values counted because that delta time...Please, send your comments ASAP. Thank's and regards,

Eduardo

[Aaron_G]

lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?Eduardo,

The FP-1600 should be sending data is relatively synchronized to the OPC Server. However, since items containing multiple analog/count channels are not allowed in the OPC Server, the OPC Server is treating the channels as separate channels and may not be transmitting the data simultaneously.

The more complete picture looks like this: The FP-1600 reads all 6 channels of the FP-CTR-500, it compares each value to the configured deadband and places any values that have changed in the transmit queue, it then does the same thing for any other I/O modules on the system. Following the scan of the entire bank, it transmits all of the changed data to the client computer. It then starts scanning the bank and the process repeats. The OPC Serv
er on the client computer breaks the data down by channels into the appropriate memory locations. An OPC Client will establish separate requests for each channel. Thus a client may sequentially request data from separate channels and may get data from different times if the OPC Client has updated channels between responding to one data request and then the next.

Regards,
Aaron

[Alfredo]

lication with OPC server. Can we assure that the time of reading of values for all the channels is the same?. We need to compare those 4 external counting values between them, using the 32 Khz internal clock like a time base reference. Can anybody help us?Aaron G,
I'm working in the same project with Eduardo.
We configured FP-CTR-500 to use:
- Channel 0&1 to create a 2 sec clock
- Channel 8 and 12 to freeze 4 counters
So we get 2 sec counting and 2 sec to get frozen 4 counters data to process them in our VB application.
We are getting, approx 30 times an hour, following error when reading counters:
Err.number: -2147188013
Err.description:"Error de Automatizacion" (Automation error?)
We obtain this error in different counters, not always the same.
Please, could you explain us this error meaning?.