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SpecView's Multiport dongle option allows the use of more than one COM port and is required in the following circumstances:

 

1. For a large number of instruments:

If the number of instruments exceeds the maximum number of instruments for communication via a single COM port. For RS485 the maximum number is typically 32 instruments. However, more can be connected if the electrical connection is very clean & if a fast response time is not particularly necessary (this may require the use of RS485 repeaters).

 

The number of controllers that can be connected to SpecView is only limited by the available addresses on the controllers.  Most instruments go to 99 addresses and SpecView supports up to 40 ports.

 

2. When instruments which use different protocols are being used:

This is because a single COM port can only communicate using one protocol. For example, if a number of instruments are all using the Modbus protocol, then they can all share a COM port, but if other instruments are added that use, say, a proprietary ASCII protocol then they would need to be connected via a separate COM port.

 

3. For greater speed of response:

When many instruments are being used in an application for which speed of response is very important then more COM ports can be used to optimize the speed of communications.

 

SpecView's maximum rate of update is once every 1 tenth of a second. However, the maximum logging rate is once per second. (Although FastCount can be used to simulate a faster logging rate.)

 

 

4. When using TCP (ethernet):

When a number of instruments are connected via TCP using different IP addresses the Multiport option is not needed - unless there are also other instruments connected by serial comms or OPC.

 

5. When using OPC:

The Multiport option will be required if it is necessary to communicate with more than one type of OPC server.

 

 

6. When using multiple instruments that use different BAUD rates or driver settings:

If these differ between instruments connected to the same COM port then they will conflict. Therefore they will need to be connected to different COM ports and the Multiport option will be needed.