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TDC-12 User’s Manual
Memory Usage in the TDC-12
The TDC-12 has a large amount of memory to store the data from your studies; the standard counter comes with 128K of static RAM. This RAM can
hold many different studies and it is unlikely that you will fill the memory
before you download the data to your computer.
There are 10 different studies in the TDC-12, and each uses a different
internal format to store the data. The following guidelines are provided to
give an idea of how much memory is used by each study type.
Five of the studies (Turning Movement, Classification, Gap, Intersection
Delay, and Travel Time) store a fixed number of bytes at regular time intervals (although the number of bytes stored each interval and the intervals
themselves vary considerably). The memory usage in these studies is fairly
easy to calculate, since it is totally a function of the length of time you do
the study. If you know how long you plan to collect data, then you can
calculate how much memory it will take.
The remaining studies (Saturation Flow Rate, Stop Sign Delay, and Spot
Speed, Turn by Class, Time-Stamp) store data (roughly speaking) on a per
vehicle basis. The memory used depends on the volume of vehicles rather
than the length of time.
The table below is a guide to help you determine if you have enough memory
in the TDC-12 to do the study you want. Only use the chart to get a rough
estimate. If it seems close, then you should arrange to download the TDC12 before doing the study.
If you run out of memory during a study, nothing serious happens. The
TDC-12 simply displays a message saying that the memory is full. No data
from previous studies are ever lost.
Turning Movement,
Classification & Gap
75 intervals for every 1% of memory
Intersection Delay
300 intervals for every 1% of memory
Sat. Flow, Turn by Class, 400 cars for every 1% of memory
Stop Sign Delay
Spot Speed
800 cars for every 1% of memory
Travel Time
10 minutes for every 1% of memory
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