Obvius BACnet User Manual

Page 12

BACnet Server for AcquiSuite

Page 12 of 52

CVS:bacnet/Documentation/BACnet_Users_Guide.doc

Generally speaking, the performance bottleneck is the connection between the AcquiSuite and the

Modbus meters – either Modbus/485 or Modhopper wireless mesh network.

This means the best data-refresh interval or logging period can be estimated from the RS485 baud rate,

the meter’s response time, the amount of data being queried from the meter, and knowledge of how many

“Modbus transactions” are needed to query all the meter’s points.

(data_bytes_per_meter * 10 bits/Byte)

refresh_interval

≈ num_meters *

[

______________________________ + (meter_response_time * blocks_per_refresh)

]

RS485_baud_rate

Note: if the meter is connected via Modhopper(s), “meter_response_time” should include 500 ms per “hop”.

The following case studies give the results of this calculation for several common situations.

Please see

for a full discussion of factors affecting

update rates.

The BACnet Server for AcquiSuite continually measures the average and worst-case response time of

each backend meter; these statistics are displayed on the

are useful for system performance tuning.