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Panel Meters - Counters - Timers - Transmitters, 4-20 mA & Modbus - Ethernet - USB - RS485 - RS232

RS232 Interface Board P/N L232 for Laurel Electronics 1/8 DIN Instruments

RS232 meter interface board

Key Features

  • Includes RJ11 connector for use with a 4 or 6-wire data cable.
  • Cable assembly available for direct connection to a PC DB9 COM port.
  • Suitable for point-to-point data communications.
  • Suitable for all 1/8 DIN Laureate DPMs, counters, timers & remote displays.
  • Selectable Modbus RTU or Custom ASCII protocols.
  • Selectable baud rates to 9600.
  • Isolated from meter and power grounds.

The Laureate RS232 serial communication board P/N L232 allows a Laureate 1/8 DIN digital panel meter, counter or timer to be interfaced to an external PC, a serial input remote display, or other device. Connection to a PC allows programming via Laurel's free Windows-based Instrument Setup Software, or to output readings to a PC for display and datalogging using Laurel's free XLOG2 software.

Laurel meter connected to PC via an RS232 serial cableRS232 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 a 6-digit Laureate remote display or a Serial Input MAGNA large digit display. These units can use the received RS232 datat 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 Laureate 6-digit remote displays 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, as listed in Laurel's communication board selection page.

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 Laureate 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 communication user manuals.


CBL01 cable. Includes DB9 and RJ11 connectors to connect a Laureate with an RS232 board a PC RS232 COM port. Plugging into the Laureate is the RJ11 connector of a common 6-wire data cable. Plugging into the COM port of a PC is custom-wired DB9-to-RJ11 adapter, which accepts the other end of the 6-wire data cable. The DB9-to-RJ11 cable assembly is sold by Laurel as P/N CBL01.

Laurel RS232 meter interface cable

CBL02 USB-to-RS232 adapter. Includes USB and DB9 connectors. Combined with a CBL01 cable (illustrated), it allows a Laureate meter with an RS232 board to be connected to a PC USB port. Note that Laurel also offers a USB board, which allows a Laureate meter to be connected to a PC USB port using a standard USB cable.

Cable assembly to connect RS232 board to PC USB port

Electrical Specifications

RS232 Board Specifications
Laurel Part Number L232
Connection RX, TX, GND, RTS (optional)
Data Rates 300, 600, 1200, 2400, 4800, 9600 baud
No. of Devices on Data Line 1 (point-to-point)
Connector Single RJ11 jack
Line Length, Max 50 to 1000 ft (15 to 300 m) depending on cable and data rate
Isolation 250V rms working, 2.3 kV rms per 1 min test
ESD Protection 15 kV per IEC 1000-4-2
EMI Immunity 10 V/m per IEC 1000-4-3
EFT Protection 2 kV per IEC 1000-4-4
Short Circuit Protection Continuous
Selectable Protocols Modbus RTU, Custom ASCII.

Protocol Specifications (protocols reside on Main Board)

Modbus RTU
Standards Compliance Modbus over Serial Line Specification V1.0 (2002)
Protocol Type Master-slave, query-response command mode
Data Streaming Mode Not supported by Modbus specification
Data Formats (selectable) 1. No parity, 8 data bits, 2 stop bits
2. Odd parity, 8 data bits, 1 stop bit
3. Even parity, 8 data bits, 1 stop bit
Applicable Interface Boards Ethernet, USB, RS232, RS485
Conversion to Modbus TCP Automatic for Ethernet
Main Board Revision Level Level 5 or above
Custom ASCII
Standards Compliance Laurel proprietary protocol
Data Format No parity, 8 data bits, 1 stop bit
Protocol Type Text string based command mode or continuous data streaming mode
Data Streaming Mode User selectable for up to 60 readings/sec
Applicable Interface Boards RS232, RS485, USB
Main Board Revision Level Any

Laurel Software Requiring a Communications Board

  • Instrument Setup Software runs on a PC and provides a Windows Graphical User Interface (GUI) as an alternative to programming the meter from the front panel. This software can be downloaded from this website at no charge. Its use requires a serial communications board in the meter, but following setup that board can be removed if desired. Compatible with Modbus or Laurel ASCII protocol.
  • Custom Curve Linearizing Software is compatible with the Extended option version of all Laureates. Not applicable to temperature. Custom curve linearization can provide exceptional accuracy from low cost transducers and extend their working range on the high and low ends. This software can be downloaded from this website at no charge. Meter setup requires a serial communications board in the meter and the Laurel ASCII protocol, but following setup that board can be removed if desired and any protocol can be used.
  • Data Logging Software turns a PC into a data logging system. The RS232 board allows data logging with a single meter. Use of RS485 boards allows data logging with up to 31 Laureate instruments. Data can be logged from selected meters into an ASCII file, which can then be imported into MS Excel. Data can also be displayed on the computer screen in the form of up to 64 actual or virtual panel meters in 4 groups (or screens) of up to 16 meters each. Compatible with Laurel ASCII protocol only.
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