AFG/AFTI Mk 4
Service and Repair Manual
Number 022-614
Issue Number: 09
Page 35 of 47
22. Latency
What is the maximum transfer rate from an AFG Mk4?
What is the latency between the data being recorded and transmitted?
The rate settings make no difference to the data transmission rates in the new
software.
1. The maximum
latency from request (e.g. receiving a ‘?’) to the start of data being
transmitted is approximately 12ms, for both RS232 (all baud rates) and Digimatic.
The data could be up to 20ms old before it is transmitted.
2. For RS232 transmission the maximum data rate depends on the format
transmitted. If units and the sign are transmitted the data rate will be reduced as
there is more to transmit.
At 9600, the guaranteed maximum rate is approximately 29Hz (continuous
transmission function operates at 25Hz at this baud rate).
At 115200 this is increased to approximately 70Hz (continuous transmission function
operates at 50Hz at this baud rate).
Note, however, that new data is only ‘available’ for transmission every 20ms, so
sampling faster than 50Hz would result in the same data being repeated
occasionally.
3. Determining the maximum data transmission rate for Digimatic is difficult as it
depends greatly on the speed the connected Digimatic device can operate at (e.g.
the Mahr printer can operate faster than some of the older Mitutoyo devices). From a
Digimatic request to complete load transmission (regardless of connected device)
takes a maximum of approximately 150ms. Therefore, theoretically, data could be
transmitted approximately every 150ms (6.6Hz) if requested. If not requested, i.e. in
continuous transmission mode, the transmission rate could be increased to a
maximum of approximately 30Hz
