Description
The RS232 serial communication board allows a DPM-3 1/8 DIN digital panel meter to be interfaced to an external PC, a serial input remote display, or other device. Connection to a PC allows programming via free Windows-based Instrument Setup software, or to output readings to a PC for display and datalogging using our DPM-3-DLS datalogging software.
RS232 is normally only used for point-to-point communications via a single data line. The RS232 request-to-send line (RTS) can be set to a latched mode, where a single reading is transmitted when the line is taken high momentarily. This mode allows a single data transfer to be commanded by another device.
RS232 can drive 6-digit remote display or a Serial Input MAGNA large digit display. These units can use the received RS232 data to display readings, to switch relays for alarm or control, and to generate a scaled analog output, such as 4-20 mA or 0-10V. Two DPM-3 can be connected to a single RS232 line in multidrop fashion without loading down the RS232 driver and be digitally addressed.
If multiple meters are to be digitally addressed by a PC or PLC, use our RS485, USB, Ethernet or WiFi boards.
Two serial protocols are user-selectable for RS232: Modbus RTU and Custom ASCII. Modbus RTU is an international Master-Slave protocol which works in a Query-Response command mode, and it requires use of an external Modbus Master. The text string based Custom ASCII protocol is the simpler of the two and is recommended if the DPM-3 is the only instrument on the data line, as would normally be the case with RS232. It can be set to a command mode or a continuous data streaming mode to send serial data in the absence of an external Master. For information on our protocols, please see our DPM-3 Serial Communication Manual.