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

4-20 mA & Serial Data Output Transmitter for Ratio, Product, Sum or Difference of 2 Rates or Totals

Applicable to Rate or Total for two pulse channels A & B. DIN Rail mounted, digitally programmable.

Transmitter for ratio, sum or difference of two pulse inputs


  • 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
  • Two independently field-scalable pulse input channels A and B
  • Arithmetic functions A+B, A-B, AxB, A/B, A/B-1 (draw) applicable to rate or total
  • Frequencies from 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
  • Analog output resolution 0.0015% of span (16 bits), accuracy ±0.02% of span
  • 5V, 10V or 24V dc transducer excitation output, isolated
  • Universal 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac power

This Laureate transmitter accepts two independently scalable input channels A & B from a wide range of pulse sources, such as NPN or PNP proximity switches, contact closures, digital logic, magnetic pickups down to 12 mV, or AC voltages to 250 Vac. Input frequencies can range from 0.005 Hz to 1 MHz.

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. These functions can be applied to scaled rates, scaled totals, square root of rates, totals after square root extraction, custom curve linearized rates, or totals after custom curve linearization.

  • Sum can be used to add two flows for total flow, or to add the number of parts carried by two conveyor belts.
  • Difference can be used to subtract outflow from inflow for net flow, or to subtract reject parts from total parts.
  • Product can be used to multiply two rates, for example to compute  horsepower by multiplying torque by RPM.
  • Ratio can be used to compare flow rates in two channels, the RPM of rollers or gears, or the speed of moving machinery, such as conveyor belts. Ratio can also be applied to scaled totals to compare two batches to be mixed. In this application, one transmitter is used to monitor the ratio of flow rates, and a second transmitter to monitor the resulting batch totals.
  • Draw is obtained by subtracting 1 from ratio. Draw is used to measure the elongation of material as it passes between rollers, or to monitor variation in the speed of rollers for tensioning.
Signal conditioner board used with 4-20 mA current transmitter for frequency, rate or period

Exceptional Accuracy and Stability. Laureate pulse input frequency and rate transmitters determine frequency by taking the inverse of period as measured with a calibrated quartz crystal time base. Extremely accurate 6-digit internal readings (±999,999 counts) are processed in software.

The update rate of the transmitter output is a programmed gate time + 30 ms + 0-2 signal periods. For pulse rates of 60 Hz and above, the update rate would be 20 per second. Such fast update rates are ideal for alarm and control.

Standard features of Laureate LT transmitters include:

  • 4-20 mA, 0-20 mA, 0-10V or -10V to +10V analog transmitter output, isolated, jumper-selectable and user scalable. All selections provide 16-bit (0.0015%) resolution of output span and 0.02% output accuracy of a reading from -99,999 to +99,999 counts that is also transmitted digitally. Output isolation from signal and power grounds eliminates potential ground loops.
  • Serial communications output, RS232 or RS485 (half or full duplex), jumper selectable. Three protocols are user selectable: Modbus RTU, Modbus ASCII, or Laurel ASCII. Modbus operation is fully compliant with Modbus Over Serial Line Specification V1.0 (2002). The Laurel ASCII protocol is simpler than the Modbus protocol and is recommended when all devices are Laureates.
  • Dual solid state relays, isolated, for alarm or control. Rated 120 mA at 140 Vac or 180 Vdc.
  • Transducer excitation output, isolated. User selectable 5V@100 mA, 10V@120 mA or 24V@50 mA.
  • Universal 85-264 Vac power. Low-voltage 10-48 Vdc or 12-32 Vac power is optional.

Easy Transmitter programming is via Laurel's Instrument Setup Software, which runs on a PC under MS Windows. This software can be downloaded from this website at no charge. The required transmitter-to-PC interface cable is available from Laurel (P/N CBL04).

Laureate 4-20 mA & RS232/RS485 Data Transmitters for Position or Rate from Quadrature Encoders
Pulse Input
Signal Types AC, pulses from NPN, PNP transistors, contact closures, magnetic 
Signal Ground pickups
Channel A Frequency Common ground for channels A & B.
Channel B Frequency 0.005 Hz to 1 MHz
Minimum Signal 0.005 Hz to 250 kHz
Maximum Signal Nine ranges from (-12 to +12 mV) to (+1.25 to +2.1V)
Noise Filter 250 Vac
Contact Debounce 1 MHz, 30 kHz, 250 Hz (selectable)
Time Base Accuracy 0, 3, 50 ms (selectable)
Arithmetic Functions Quartz crystal calibrated to ±2 ppm A+B, A-B, AxB, A/B, A/B-1
Analog Output (standard)
Output Levels 4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10Vdc (user selectable)
Compliance at 20 mA 10V (0-500Ω load)
Compliance, 0-10V 2 mA ( 5 kΩ or higher load )
Output Resolution 16 bits (65,536 steps)
Output Accuracy ±0.02% of output span
Output Update Rate Programmed gate time + 30 ms + 0-2 signal periods
Output Isolation 250V rms working, 2.3 kV rms per 1 minute test
Serial Data Output (standard)
Signal Types RS232 or RS485 (half or full duplex), jumper selectable
Data Rates 300, 600, 1200, 2400, 4800, 9600, 19200 baud
Output Isolation 250V rms working, 2.3 kV rms per 1 min test
Serial Protocols Modbus RTU, Modbus ASCII, Laurel ASCII
Modbus Compliance Modbus over Serial Line Specification V1.0 (2002)
Ethernet Connector RJ45 jack for 10/100 Base-T Ethernet cable
RS232/RS485 Connector  Screw terminals for easy daisy chaining 
Digital Addresses 247 for Modbus, 31 for Laurel ASCII
Dual Relay Output (standard)
Relay Type Two solid state relays, SPST, normally open, Form A
Load Rating 120 mA at 140 Vac or 180 Vdc
Sensor Excitation Output (standard)
Output Levels 5V@100 mA, 10V@120 mA, 24V@50 mA (jumper selectable)
Output Isolation 50V from signal ground
Power Input
Standard Power 85-264 Vac or 90-300 Vdc
Low Power Option 10-48 Vdc or 12-32 Vac
Power Frequency DC or 47-63 Hz
Power Isolation 250V rms working, 2.3 kV rms per 1 min test
Power Consumption 2W typical, 3W with max excitation output
Dimensions 129 x 104 x 22.5 mm case
Mounting 35 mm rail per DIN EN 50022
Electrical Connections Plug-in screw-clamp connectors
Operating Temperature 0°C to 55°C
Storage Temperature -40°C to 85°C
Relative Humidity 95% at 40°C, non-condensing
Cooling Required Mount transmitters with ventilation holes at top and bottom. Leave 6 mm (1/4") between transmitters, or force air with a fan.
Laureate LT transmitter pinout
Applications Examples
Controlling the Mixing Ratio of Two Fluids
Using a ratio meter to control the mixing ratio of two fluids Transmitting and alarming the input flow rate ratio of two fluids (gas or liquid) allows these to be mixed in a predetermined ratio in continuous processes. The sensing element is normally a turbine flow meter, which outputs pulses at a frequency proportional to flow rate. The A/B ratio can also be transmitted for totalized rate (or delivered volume).
Comparing Fluid Inflow & Outflow
Using a ratio meter to compare fluid inflow and outflow The ratio of the inflow and outflow rates of a tank is a measure of the relative filling or emptying rate. The same transmitter can also be programmed to transmit the net inflow or outflow rate in flow units, or to transmit totalized inflow our outflow in volume units. Any of these parameters can be alarmed using the dual relay board and be transmitted via 4-20 mA.
Controlling Coating Thickness on a Film
Using a ratio meter to control coating thickness on a film In this application, Channel A measures the rate at which a coating material is applied, as measured by a flow meter, while Channel B measures the speed of the film based on pulses from a proximity switch. Transmitting and alarming the A/B ratio assures that an even thickness of coating material is applied as the speed of the film is varies.
Instrumenting a Pulsed Laser System
Using a ratio meter to synchronize two conveyor lines The dual-channel Laureate transmitter can measure the speed of conveyor lines by using the output of proximity switches which sense gear teeth or spokes of rotating drive wheels. Transmitting the speed ratio of two lines allows line speeds to be adjusted so that material arrives at work stations when needed.
Measuring Draw for Elongation
Using a draw meter to display and control elongation of film between rollers Draw (Ch A / Ch B - 1) can be used to indicate the elongation of films compressed between rollers, the shrinkage films, and the RPM difference of rollers whose speed is varied to maintain tension. The high resolution of Laureate dual channel transmitters is ideal for comparison of rates that are close to each other.
Ordering Guide
Laureate Transmitter for Ratio, Product, Sum or Difference of 2 Rates or Totals
Click on the radio buttons to build a model number with pricing as shown below. Prices are in US dollars and do not include shipping or duty charges (export sales). Please see our explanations and limitations applicable to pricing and online orders. Prices shown are in US Dollars and are Laurel's manufacturer's suggested retail price (MSRP) in the USA. Orders are processed manually, not directly by our shopping cart system. You don't have to supply credit card information when placing an online order.

North American Orders. Laurel does not sell factory-direct in the USA or Canada. Online sales orders are filled through distribution. During the ordering process, you will have the chance to select an authorized Laurel distributor, or you can ask Laurel to refer you to a distributor. The distributor will then contact you to quote shipping, tax and duty (where applicable), and arrange for payment.

International Orders. If your ship-to address indicates that you are outside of the USA or Canada and Laurel has a distributor in your country, we will forward your order to that distributor for follow-up. If Laurel does not have a distributor in your country, we will email you an order acknowledgment and a pro forma invoice which states the product price, shipping charges, and wire transfer information, which includes a $25 bank wire transfer fee.

Questions about your order? Please email your distributor or
Configured model number LT80FR
Configured price per model $275
Quantity 1
Extended price $275
LT  4-20 mA & RS232/RS485 output transmitter $235
LTE  4-20 mA & Ethernet output transmitter $295
Main Board 8  Extended Main Board (required for arithmetic functions) $40
Power 0  Isolated 85-264 Vac or 90-300 Vdc $0
1  Isolated 12-32 Vac or 10-48 Vdc $30
Input Type FR  Dual-Channel Pulse Input $0
Accessories CBL04  RS232 cable, 7ft. Connects RS232 screw terminals of LT transmitter to DB9 port of PC. $19
CBL02  USB to RS232 adapter cable. Combination of CBL02 and CBL04 connects transmitter RS232 terminals to PC USB port. $39
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