Note: This topic applies to RemoteLog RTUs, VersaTRAK and Mini-VersaTRAK RTUs and legacy SixTRAK programmable gateways.
The amount of data to log is limited only by available memory in the station. Just how much data can a legacy SIXNET station store? Here’s an easy way to calculate the required file size and the length of time you can store data before running out of memory.
STEP 1 - Calculate the number of bytes used per sample:
each analog register uses two bytes
eight discrete registers pack into a single byte
longs and floats use four bytes per register
each time/date stamp or millisecond timer is a long integer (four bytes)
Take the number of discrete points per sample and divide it by 8. Add that to the number of analog points multiplied by 2. Then add four bytes for the time stamp.
Example: Datalogging 80 discrete and 20 analog points = 10 + 40 = 50 bytes per sample. Add 4 bytes per sample for time stamping. The number of bytes/sample = 54.
STEP 2 - Calculate the number of samples per day:
Example: Sampling every 10 minutes = 1440 (mins. per day) ÷10 = 144 samples per day.
STEP 3 - Calculate bytes per day (samples per day multiplied by bytes per sample).
Example: 144 x 54 = 7776 bytes per day.
STEP 4 - Calculate how many days you can log data before reaching a given file size:
Divide "Default Datalogging Memory" by bytes per day:
Example: 96,000 bytes ÷ 7776 bytes per day = approximately 12.34 days.
The following chart compares the data storage capability of the various SIXNET stations that support datalogging.
|
Station Type |
Memory Option |
Default Datalogging Memory |
# I/O Points Logged |
# Bytes per Sample |
Sampling Rate |
Desired File Size |
Days of Storage |
|
SixTRAK Gateway, VersaTRAK RTU |
-24P |
96K Bytes * |
100 Discrete |
18 |
1 Minute |
76.8K Bytes |
3 Days |
|
"" |
-44P |
768K Bytes * |
100 Discrete |
18 |
1 Minute |
700K Bytes |
27 Days |
|
"" |
-54P |
1792K Bytes * |
100 Discrete |
18 |
1 Minute |
1700K Bytes |
65 Days |
|
RemoteLog RTU and Datalogger |
|
Approx. 750K Bytes |
6 Analog In, |
18 |
1 Minute |
726K Bytes |
28 Days |
* With these controllers only, some of the available datalogging of memory is used for I/O registers and your ISaGRAF program. The SIXNET I/O Tool Kit’s Resource Allocation Window (accessed from the configuration window for the station) allows you to slightly increase or decrease the amount of datalogging memory, according to the size of your ISaGRAF program.
Is this enough data storage?
Keep in mind that Sixlog datalogging is just a front end buffer for your Windows software. You only need to store data in the SIXNET station until it is transferred to the hard disk in your computer.