Modem (Landline) - Data Logger Connection:

Setting up a remote modem:

Download Datasheet


DLCA adaptor connected to Modem

Overview:

The TruTrack loggers can use modem links both for general communications with a computer and to dial a pocket pager when alarm conditions occur. A special modem adaptor is required between the logger and the modem (DLCA). The connection required for general communication is identical to that required to dial a pocket pager.

Modem schematic

The logger is connected to a modem with a DLC# RS232 download cable and a DLCA download cable crossover adaptor. The modem is connected to the telephone network. The logger can now be controlled by any computer with a modem that is connected to the telephone network. The logger can also be configured to send a message to a pocket pager on the telephone network if user specified alarm conditions occur.

The data loggers communicate at 19200 baud. Any Hayes Compatible Modem that can lock the logger to modem baud rate to 19200 can be used with these loggers. Some modems will try to autoseek the incoming baud rate from the logger. This type of modem cannot be used with these loggers.

Notes:

  • The cable connecting the Remote Modem to the Logger must not exceed 15 meters without a booster (RS232 standard).
  • It is NOT possible to use a remote USB modem and a DLC#USB download cable to connect to the logger. An RS232 Modem with a DLC# RS232 download cable and a DLCA download cable crossover adaptor MUST be used.

Remote Modem Setup in OmniLog:

To use a remote modem with OmniLog requires the modem to be setup correctly. The easiest way to do this is to use OmniLog with the remote modem attached to the computer.

Remote Modem Setup Screen in OmniLog (Access via 'General Toolbox' under 'Tools').

Remote modem setup

See the instructions in the PDF above for full details on setting up a remote modem.

Note: DO NOT setup the Modem that is connected to the computer end as a Remote Modem, as it will not function with OmniLog! No setup is necessary for the modem that is used at the computer end other than installing it with Windows.

 

Connecting to the logger via the remote Modem:

The Modem Control screen is used to connect to the Remote Modem.
Modem Control Screen in OmniLog (Access via 'Tools' Menu or hitting keys Ctrl+M).
Modem control

Once the remote modem connects the usual logger status screen appears and all normal functions can be performed including logger start/stop and download of data.

 

Connecting to the remote Modem under difficult conditions:

Software modems commonly used in Laptop computers may experience intermittent connection to the remote modem. This appears to be a particular problem with those software modems based on the 'Lucent' chipset.

Try the following step to see if there is an improvement in connectivity:
Tools> Options> Comms tab and check the "Safe Modem Mode for difficult connections" box:

Difficult connections setting

If ticking "Safe Modem Mode for difficult connections" does not work, there is a second option.
If you add a modem phone number to the Phone Book there is a text box named "Before ATDT"
This field is used to send a string of special configuration data to the modem before it dials the number.
You get to the phone book from Tools> Phone Book.

Phone book

If you add a number or edit an existing number the "Before ATDT" text box is available.
There are two buttons at the bottom of this Phone Book edit screen.
One is labeled AT+ms=V32b,0<CR>
The other is labeled AT+ms=10,0<CR>
Click AT+ms=V32b,0<CR> and this string will be added to the "Before ATDT" text box.

Command string

Click OK
Then try dialing the external modem and see if this has fixed the problem.
If this does not fix the problem try the AT+ms=10,0<CR> string
These commands force Lucent software modems to negotiate an acceptable protocol with the external remote modem.
If this fixes the problem, turn off "Safe Modem Mode for difficult connections".
"Safe Modem Mode for difficult connections" causes the system to run with a reduced baud rate and is therefore slower than normal mode.

Intech Instruments' recommends the use of external hardware modems at both ends of the connection (I.e. not just the remote modem), as these are far more robust than internal software modems, especially under 'noisy' line conditions.