Instruction manual

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Appendix B. Memory Usage
Each mode uses a different amount of memory for storing traffic data. This appendix is intended to give the user an
approximation of how long a Phoenix II field unit may collect data before retrieval of data files. Note that this is only a
guide. It is recommended to retrieve data as often as is practical from the units and deleting retrieved files from the
memory. Different configurations may store different amounts of data. For example, the amount of memory to store
a single 2 axle vehicle in Raw Mode is 7 bytes using axle sensors. A 5 axle vehicle in the same mode will take 13 bytes
using axle sensors.
The following tables give you formulas for calculating how much memory any particular storage mode might take.
Simply find the table that most closely matches your application and follow the steps described. To quickly find our
counters Total Memory, refer to Section 4.4 and use the top Total Mem number.
Appendix B.1 Raw Data Collection
Raw data stores each individual vehicle in memory; therefore, the amount of memory used is directly dependent upon
how many and of what type of vehicles pass the sensors. Another important factor is the number of axles per vehicle
(more axles require more memory).
Generally, you can use the average of 2.75 axles per vehicle for most highways. If your site differs from this, you may
wish to increase or decrease this number in the example below.
To calculate how many vehicles you can store with the Phoenix II, follow these steps:
SENSOR CONFIGURATION
NORMAL RAW DATA
ENHANCED RAW DATA
RAW DATA WITH BINS
ENHANCED & BINS
Axle Axle
Axle Loop Axle
Loop Axle Loop
8.5
12.5
13.5
17.5
Loop Loop
7
9
12
14
Divide the Total memory of your counter minus 2000 (for overhead) by the base number of bytes from the chart
above. The total amount of memory in your counter can be found using the Show Status option, Section 4.4. A
standard Phoenix II contains 968 Kbytes, which gives over 1 million axle strikes for Normal Raw Data.