Black Box Converter Testing

While B+B Electronics 20 ma to RS-232 converters are generally very reliable, in a mill environment things can happen. The major problem is fallout from nearby lightning strikes, which can damage electrical and electronic devices. Because these Black Box converters are generally used on long signal cables going from the control room to scales and boxes located out in the yard, these long cable runs are vulnerable to lightning damage

If damage is suspected, execute the following steps to test a converter:

• Document the existing converter wiring. Draw a schematic. Take a picture.
  
  
• Dewire and remove the converter and power supply. If your converter doesn't have a power supply connected to it, any 12 volt DC power supply should work. Just be sure to get the polarity correct when wiring so as to not damage a potentially good converter.
  
  
• Rewire the converter as shown:
  
  Click to download a PDF copy of the above schematic.
  
  
• Plug the converter into a laptop serial port. If your laptop doesn't have a serial port, plug it into a USB to RS-232 Port adapter, and plug the adapter into a laptop USB port. You may have to install a driver supplied with the USB adapter.
  
  
• Run HyperTerminal (or equivalent serial port utility) and select the proper serial port. Serial parameters, like baud rate, etc. can be left at default values (typically 9600 baud), as they don't matter for this test.
  
  
• Anything you type in the test screen should be echoed back. This is because the converter is wired to return any data on its transmit port to its receive port. For this to be successful, all converter functions must be operating properly.