Load Cell & Microvolt Input Modbus or Laurel ASCII Protocol Serial I/O Transmitter

DIN Rail Mounting.  Laureate transmitters are housed in a 35 mm DIN rail case that is only 22.5 mm (0.89") thick. Signal connections are via detachable screw clamp plug connectors.

Modbus Compliance.  Laureate Modbus transmitters are fully compliant with Modbus over Serial Line Specification V1.0 (2002). This includes RTU or ASCII modes, 2-wire connection, up to 247 digital addresses, and up to 32 devices per RS-485 line without a repeater. For microvolt DC or load cell signal inputs, output accuracy is ±0.01% of full scale input, as provided by the 16-bit analog-to-digital converter front end. Full conversion accuracy is maintained in the Modbus output. Advanced standard features made possible with Modbus operation include peak capture, auto-tare and latched relay operation, since Reset can be provided via digital commands.

Built-in Load Cell Excitation

An isolated 10 Vdc, 60 mA excitation supply rated can power up to two 350-ohm load cells in parallel. With 4-wire load connection, the transmitter operates in a ratiometric mode to eliminate errors due to supply variations. With 6-wire load connection, it also compensates for variation in resistance of the transducer leads, thereby allowing long cable runs.

Fast Read Rate

All Laureate analog input meters and transmitters use Concurrent Slope (Pat 5,262,780) analog-to-digital conversion, which allows up to 50 or 60 conversions per second, while integrating the signal over a full power line cycle. High read rate is ideal for peak capture and for real-time computer interface and control.

Selectable Signal Filtering

The internal digital readings and analog output can be separately selected to be either unfiltered or filtered.

• An unfiltered selection updates after each conversion for fastest response, up to 60/sec, while integrating the input signal over a full power cycle. Fast read rate provides true peak readings and aids in control applications.

• A batch average filter selection averages each 16 conversions for an update every 1/4 sec.

• An adaptive moving average filter selection provides a choice of 8 time constants from 80 ms to 9.6 s. When a significant change in signal level occurs, the filter adapts by briefly switching to the shortest time to follow the change, then reverts back to its selected time constant. Another choice is Auto, which provides an automatic time constant selection based on the signal noise characteristics.

Easy Setup & Scaling

Transmitter programming is via a three-terminal RS-232 port using Laurel's PC-based Instrument Setup Software. This software can be downloaded from this website at no charge. The required transmitter-to-PC interface cable is available from Laurel (P/N CBL03). Laurel's serial output transmitters and meters can also be part of PC-based data logging systems using Laurel's Datalogging Software, which operates under the Laurel ASCII Protocol. A single software command switches between the Modbus and Laurel ASCII Protocols.

Scale and offset can be set by either of two methods:

• With the coordinate reading method, the Laureate reads the high and low signal values, and the user enters the desired high an low reading values. The Laureate then calculates the span multiplier and offset. This method is ideal if an external calibration reference is available.

• With the manual coordinate method, the user enters the high and low input values in Volts plus the desired high and low reading values. This method is suitable if no external calibration reference is available.

Options

Options include dual solid state relays for local alarm or control and an isolated 4-20 mA or 10V (selectable) analog output, effectively providing a linearized analog transmitter output that tracks the reading that would be transmitted digitally. The analog output provides 12-bit (4096 step) resolution of the output span and is ultra-linear to within one bit. Its accuracy is ±0.05% of span for all signal types, except for AC rms, where accuracy is ±0.1%. Output isolation from signal and power grounds is provided by a separate on-board power supply, which can drive 20 mA into a 500 ohm load for 10V compliance. Output isolation eliminates problems caused by ground loops.