LT-FR

4-20 mA & Serial Data Transmitter for Pulse Signal Arithmetic

Laurel Electronics Inc.

  • 4-20 mA, 0-20 mA, 0-10V, or -10V to +10V transmitter output, 16 bits, isolated.
  • RS232 or RS485 serial data output, Modbus or Laurel ASCII protocol, isolated.
  • Dual 120 mA solid-state relays for alarm or control, isolated.
  • Arithmetic functions: A+B, A-B, AxB, A/B, A/B-1.
  • Input frequencies: 0.005 Hz to 1 MHz.
  • Inputs from NPN or PNP proximity switches, contact closures, digital logic,
  • magnetic pickups down to 12 mV, or AC inputs up to 250 Vac

Details

This transmitter is specifically designed to process signals from two independent input channels (A and B), enabling it to perform precise calculations such as ratio, product, sum, or difference of rates or totals. It is highly versatile, accepting signals from a variety of pulse sources, including NPN or PNP proximity switches, contact closures, digital logic, magnetic pickups down to 12 mV, and AC signals up to 250 Vac. With a wide input frequency range from 0.005 Hz to 1 MHz, the transmitter is well-suited for both low-speed and high-speed applications.

Arithmetic functions A+B, A-B, AxB, A/B or A/B-1 are made available by the Extended counter main board and can track the sum, difference, product, ratio, or draw of both input channels.

  • Addition (A + B): Combine two flows for total flow measurement or count parts on two conveyor belts.
  • Subtraction (A - B): Calculate net flow by subtracting outflow from inflow, or remove rejected parts from total counts.
  • Multiplication (A × B): For example, compute horsepower by multiplying torque by RPM.
  • Division (A / B): Compare two flow rates, RPM of gears or rollers, or the speeds of moving machinery like conveyor belts.
  • Draw (A / B - 1): Measure elongation of material between rollers or monitor speed variation for tensioning.

These functions can be applied to scaled rates, totals, square root values, or custom linearized rates and totals, making it suitable for complex calculations in industrial processes.

Exceptional accuracy and stability are achieved using a calibrated quartz crystal time base, providing precise measurements of frequency, rate, or period with internal six-digit precision (±999,999 counts). The transmitter’s output updates rapidly, with rates configurable based on signal frequency and gate time, making it ideal for applications that require real-time monitoring and control, such as alarms or automated systems. The built-in flexibility and precision of this transmitter make it a dependable choice for demanding industrial environments.

Specifications

Interface
RS-232
RS-485
Input Type
Frequency
AC voltage
Output Type
0 - 10 V DC
±10 V DC
0 - 20 mA
4 - 20 mA
Excitation
5 V DC
10 V DC
24 V DC
Isolation
Yes
Min Temperature
0°C
Max Temperature
55°C

Models

LT-FR
Transmitter for Ratio, Product, Sum, or Difference of Two Rates or Totals
LT80FR
4-20 mA & RS232/RS485, Extended Main Board, Isolated 85-264 Vac or 90-300 Vdc

Downloads

transmitter-ratio-Datasheet