2400 2.40 seconds
4800 1.60 seconds
9600 1.20 seconds
19,200 1.00 seconds
Once the worse case delay times are determined, the maximum speed at which 16 Tags can move past
Readers can be calculated by determining the length of the Reader Antennas' read fields and substituting
that length and the delay time into the familiar equation R * T = D, rate times time equals distance. For
example, if Tags travel past Reader Antennas with read fields of 0.7 foot and the Model 2022 is set to
19200 baud:
Max Rate * 1 sec = 0.7 ft
Max Rate = .7 ft / 1 sec or 0.7 foot per second
A more general worse case delay equation may be written to evaluate systems without as many
constraints as the system above. For example, there could be a Model 2022 with 16 Readers but only
2 possible Tags to be read. Although it takes 50 milliseconds plus transmission time to report a Tag, it
takes a maximum of 30 milliseconds for the Model 2022 to determine that there is no Tag. The Model
2022 can also be instructed to ignore certain Readers via the Assign Command. This impacts the
worse case system delay time because the Model 2022 doesn't spend any time looking at omitted
Readers. The equation to calculate system delay time (Td) works out as follows:
Where: Tr = 50 milliseconds it takes to read and process
Tn = 30 milliseconds it takes to check a Reader w/o Tag
Tt = Transmit time for complete Tag, see table below
#P = # of possible simultaneous reads
#S = # of Assigned Readers
Td = #P * (Tr + Tt) + (#S - #P) * Tn
To save you some time, Tt is calculated below for the 8 possible baud rates based and all possible
number of bits per character available with the different transmission configurations. When calculating
the number of bits per word don't forget to count the Start Bit.
BAUD RATE 9 10 11 12
110 1.636364 1.818182 2.000000 2.181818
300 .600000 .666667 .733333 .800000
600 .300000 .333333 .366667 .400000
1200 .150000 .166667 .183333 .200000
2400 .075000 .083333 .091667 .100000
4800 .037500 .041667 .045833 .050000
9600 .018750 .020803 .022917 .025000
19200 .009375 .010417 .011458 .012500
The equation can be used to prove the results of the worse case delays calculated earlier. A Model
2022 with 16 Readers and 10,000 Tags has #P of 16 since only 16 can be read at once, if the Model
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