PLC Data usage on sim connection

Hello All,

I'm looking to receive data remotely from a site, and was looking to get connectivity to the site via a 3g connection. Does anyone know how much data I would need if reporting from 4 different water sensors measuring Ph levels.

dilanjivanji said:

Hello All,

I'm looking to receive data remotely from a site, and was looking to get connectivity to the site via a 3g connection. Does anyone know how much data I would need if reporting from 4 different water sensors measuring Ph levels.

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Work it out ?

It's fairly simple if you have the figures in front of you, just work out how often you need the data each day, what the size of the data is you are transferring then multiply that by a 30 days.

Hi Tragically,

Unfortunately I don't have the figures in front of me, as I'm still looking at the costing of the system.

dilanjivanji said:

Hi Tragically,

Unfortunately I don't have the figures in front of me, as I'm still looking at the costing of the system.

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OK, so if you can't work it out how is somebody else going to ?

A VERY simple, VERY quick worked example:

Each sensor will give a reading as a 16 bit number each hour = 64 bits per hour, 24 hours = 1536, 1536 x 30 days= 46080 bits per month, 46080 = 0.00576MB

NOTE: As i say, VERY quick, VERY simple so the usual caveats apply.

Or alternatively if the process is important enough to be monitored remotely why buy per MB, just go unlimited......

Hello Tragically,

Thank you for your help, I now understand how the calculation gets done. This is all new to me, so its great to have assistance.

dilanjivanji said:

Hello Tragically,

Thank you for your help, I now understand how the calculation gets done. This is all new to me, so its great to have assistance.

Click to expand...

Like i say VERY simple, there will be an overhead for your messaging depending on what protocol it is.

For example a Modbus message can be a maximum of 256 bytes transferring up to 252 bytes of data so just do your calcs. based on the maximum message size of the protocol used.

Note that the overhead per message over Ethernet will most likely be at least 46 bytes.

Per some googling:

The Ethernet header takes up 18 bytes, the IPv4 header 20 bytes, and the UDP header 8 bytes.

The TCP header would be a little more than UDP, depending on which protocol is used. Note also that the minimum Ethernet frame is 64 bytes, so if you need to send less than 18 bytes (64 total - 46 header = 18 payload), it will add padding (empty data) until it gets big enough.

If you have multiple data points to be sent at the same time, this will save data, as the header only has to be sent once for each group of samples.