Features
- 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
- Inputs from NPN or PNP proximity switches, contact closures, digital logic, magnetic pickups down to 12 mV, or AC inputs up to 250 Vac
- Two independently field-scalable pulse input channels from 0.005 Hz to 1 MHz
- 4-20 mA, 0-20 mA, 0-10V or -10V to +10V transmitter output, (isolated)
- Analog output resolution 0.0015% of span, accuracy ±0.02% of span
- RS232 or RS485 serial data, Modbus or Laurel ASCII protocol (isolated)
- Dual 120 mA solid state relays for alarm or control (isolated)
- 5V, 10V, 12V, or 24V dc transducer excitation output (isolated)
- Power 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac (isolated)
- DIN rail mount housing, 22.5 mm wide, detachable screw-clamp connectors
- Operating temperature from 0°C to 55°C
- Operating temperature option from -40°C to 70°C (-40°F to 158°F)
- Extended allows up to 180 data points for custom curve linearization and a rate derived from consecutive readings along with arithmetic functions A+B, A-B, AxB, A/B or A/B-1
Certificates of Compliance
The Laureate 4-20 mA, 0-20 mA, 0-10V or -10V to +10V and RS232/RS485 output transmitter for ratio, product, sum or difference of 2 rates or totals 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.
The Extended Laureate computer board can display rate based on successive readings. It also allows exceptionally accurate custom curve linearization, for example to read out liquid volume or rate of flow in a horizontal cylindrical tank based on level reported by a 4-20 mA transmitter. For setup, up to 180 data points can be input into a computer spreadsheet or text file by the user. The computer then calculates spline-fit segments, which are downloaded into the transmitter.
Exceptional Accuracy and Stability. Laureate transmitters determine frequency by taking the inverse of period as measured with a calibrated quartz crystal time base. This results in extremely accurate and stable 6-digit internal readings (±999,999 counts), which are then processed in software. The analog output is generated by an ultra-linear 16-bit (65,536 step) digital-to-analog converter (DAC) for 0.02% output accuracy. The update rate of the transmitter output is a programmed gate time + 30 ms + 0-2 signal periods. For a 60 Hz signal, the update rate would be 20 per second. Such fast update rates are ideal for alarm and control.
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.
All signal conditioner board ranges are factory-calibrated, with calibration factors for each range securely stored in an onboard EEPROM. These factors can be scaled via software to accommodate external shunts, enabling field replacement of signal conditioner boards without necessitating recalibration of the associated transmitter. For optimal accuracy, factory recalibration is recommended annually. All Laurel Electronics instruments undergo factory calibration using the industry-leading Fluke calibrators, which are recalibrated yearly and certified traceable to national standards, ensuring the highest level of precision and reliability.
Laureate Transmitters are easily programmed with Laurel’s free Instrument Setup Software, downloadable from our website and compatible with Windows PCs, requiring a data interface board for setup.
Standard Features of Laureate LT Transmitters Include:
- Serial communications output, (isolated), 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.
- 4-20 mA, 0-10V or -10V to +10V analog transmitter output, (isolated), jumper-selectable and user scalable. All selections provide 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 loop problems. Note that Ethernet data I/O is provided by Laurel's LTE series transmitters.
- Dual-channel pulse inputs for voltage signals, NPN or PNP proximity switches, contact closures, magnetic pickups or flow meters.
- Dual solid state relays, (isolated), for alarm or control. Rated 120 mA at 130 Vac or 170 Vdc.
- Selectable transducer excitation output, (isolated), user selectable 5V@100 mA, 10V@120 mA, 12V@100 mA, or 24V@50 mA.
- Power 85-264 Vac, (isolated), low-voltage 10-48 Vdc or 12-32 Vac power is optional.
Digital signal filtering modes can be selected to ensure stable readings in electrically noisy environments.
- An unfiltered selection provides true peak and valley readings and aids in control applications.
- A batch average filter selection averages each 16 conversions.
- An adaptive moving average filter selection provides a choice of 8 time constants from 80 ms to 9.6 seconds. 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. An Auto setting selects the time constant selection based on signal noise.
Peak and valley values are automatically captured. These may be displayed via Laurel's free Instrument Setup Software, which runs on a PC under MS Windows or can be transmitted as serial data.
Two control inputs (CMOS/TTL levels, logic 0 = tied to digital ground, logic 1 = open) or dry contacts that can be set to control / activate 14 transmitter commands.
An (isolated) 5, 10, 12, or 24 Vdc excitation output is standard to power transducers or two-wire transmitters. Ratiometric operation, which automatically compensates for changes in the applied excitation, is jumper selectable for applications, such as bridges, where the signal to be measured is proportional to the excitation level.
LT series DIN rail Transmitters & signal conditioners can be interfaced to a wide range of sensors and transducers using one of seven available plug-in signal conditioner boards. The transmitters duplicate the high performance (high accuracy, high read rate) and extensive programmable features of Laureate 1/8 DIN digital panel meters, counters and timers. They utilize the same signal conditioners boards, much of the same firmware, and Laurel's free Windows-based Instrument Setup Software. They come in a compact DIN rail mount package with detachable screw-clamp connectors for easy wiring.
The LT series Transmitters accessible from this page include a 4-20 mA, 0-20 mA, 0-10V, or -10V to +10V analog output (isolated, user selectable), an RS232 or RS485 serial data interface (isolated, user selectable), and dual 120 mA solid state AC/DC relays (isolated). An (isolated) 5, 10, 12, or 24 Vdc transducer excitation output is included with all models other than those with a temperature or AC RMS signal conditioner.
Connecting Laureate LT Transmitters to a Local Area Network (LAN)
Up to 30 Laureate LT Transmitters and/or Digital Panel Meters can be configured for RS485 and daisy-chained to an LT Transmitter for seamless LAN integration. Alternatively, Laurel LTE series Ethernet transmitters can connect directly to a LAN via an Ethernet cable. Setup for both configurations is streamlined using Laurel’s free Instrument Setup Software, which simplifies node discovery and transmitter configuration.
Flexible Communication Options for LT Transmitters
Laureate Transmitters can be equipped with Laurel communication boards to support various interfaces and protocols. These include serial interfaces with ASCII or Modbus RTU protocols, and Ethernet interfaces with web access, ASCII, or Modbus TCP/IP protocols, ensuring versatile connectivity for your commercial applications.
| LT Transmitter Signal Input & Function | Model Series | Analog Output | RS232 & RS485 | Dual Relays | |
|---|---|---|---|---|---|
| 1 | DC Input Voltage and Current | LT-DC |  |
|
|
| 2 | AC RMS Voltage or Current | LT-RMS | |
|
|
| 3 | Process Voltage or Current | LT-P | |
|
|
| 4 | Weighing Applications | LT-WA | |
|
|
| 5 | Load Cell & Microvolt Signals | LT-WM | |
|
|
| 6 | Thermocouple (Types J, K, T, E, N, R, S) | LT-TC | |
|
|
| 7 | RTD Temperature | LT-RTD | |
|
|
| 8 | Resistance in Ohms | LT-R | |
|
|
| 9 | Frequency, Rate, Speed | LT-FR | |
|
|
| 10 | Pulse Input Totalizer | LT-FR | |
|
|
| 11 | Process Signal Totalizer | LT-VF | |
|
|
| 12 | Sum, Difference, Ratio, Product of 2 Inputs | LT-FR | |
|
|
| 13 | Batch Controller Pulse Input | LT-FR | |
|
|
| 14 | Batch Controller Analog Input | LT-FR | |
|
|
| 15 | On/Off Duty Cycle | LT-FR | |
|
|
| 16 | Stopwatch Timing for Single Events | LT-FR | |
|
|
| 17 | Average Time of Periodic Events | LT-FR | |
|
|
| 18 | AC Phase Angle and Power Factor | LT-FR | |
|
|
| 19 | Quadrature Position or Rate | LT-QD | |
|
|
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 | |||
| Recalibration: All ranges are calibrated at the factory. Recalibration is recommended every 12 months. | ||||
| 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, Custom ASCII | |||
| Modbus Compliance | Modbus over Serial Line Specification V1.0 (2002) | |||
| RS232/RS485 Connector | Screw terminals for easy daisy chaining | |||
| Digital Addresses | 247 for Modbus, 31 for Custom 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 | |||
| Excitation Output (standard) | ||||
| 5 Vdc | 5 Vdc ± 5%, 100 mA (jumper selectable) | |||
| 10 Vdc | 10 Vdc ± 5%, 120 mA (jumper selectable) | |||
| 12 Vdc | 12 Vdc ± 5%, 100 mA (jumper selectable) | |||
| 24 Vdc | 24 Vdc ± 5%, 50 mA (jumper selectable) | |||
| Output Isolation | 50 Vdc 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 at 24V | 1.5W typical, 3W with max excitation output | |||
| Environmental | ||||
| Operating Temperature | -40°C to 70°C (-40°F to 158°F) | |||
| Storage Temperature | -40°C to 85°C (-40°F to 185°F) | |||
| 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. | |||
| Mechanical | ||||
| Enclosure | Rugged black polycarbonate housing material | |||
| Mounting | 35 mm rail per DIN EN 50022 | |||
| Dimensions | 129 x 104 x 22.5 mm case | |||
| Connectors | Detachable screw clamp connectors meet VDE / IEC / UL / CSA standards. RJ45 jack for Ethernet | |||
| Tightening Torque | Screw terminal connectors: 5 lb-in (0.56 Nm) | |||
| Weight | Complete transmitter: 183 g (6.5 oz) | |||
| Replacement Case Screws | ||||
| Size | 6 | |||
| Thread Pitch | 6-19 | |||
| Length | 1/2" | |||
| Head Style | Pan Head | |||
| Drive Style | Phillips | |||
| Head Diameter | 0.256-0.270 | |||
| Head Height | 0.087-0.097 | |||
| Full/Partial Thread | Full | |||
| Drive Size | 2 | |||
| Material | Steel | |||
| Finished | Black Oxide | |||
| General | ||||
| Programming | Utilize Laurel's free Instrument Setup Software, which runs on a PC under MS Windows. | |||
| Security | Lockout options available using Laurel's free Instrument Setup Software. | |||
| Warranty | 3 years parts & labor | Recalibration: All ranges are calibrated at the factory. Recalibration is recommended every 12 months. | ||
Transmitter Pinout
Free Instrument Setup Software for Series 2 Laureates
|
|
| 1/8 DIN Digital Panel Meters | DIN Rail Transmitters |
Free Downloadable Windows-based Instrument Setup (IS) software (Data Interface Board Required) for use with our programmable Digital Panel Meters, Scale Meters, Counters, Timers, Remote Displays, and Transmitters, are an easy method to set up Laureate 1/8 DIN digital panel meters, counters, timers, remote displays, and DIN-rail transmitters, as explained in the Instrument Setup Software Manual. Laureate 1/8 DIN instruments can also be set up from the front panel, as explained in their respective Owners Manuals. Instrument Setup software is of benefit whether or not the PC is connected to the instrument.
- When the PC is connected to the instrument, Instrument Setup software can retrieve the setup file from the instrument or open a default setup file or previously saved setup file from disk View Setup, then provides graphical user interface (GUI) screens with pull-down menus applicable to input, display, scaling, filtering, alarms, communications, analog output, and front panel lockouts. Fields that are not applicable to the instrument as configured are either left out or grayed out. Clicking on any item will bring up a detailed Help screen for that item. After editing, the setup file can be downloaded, uploaded to the instrument, or saved to a disk. The same setup file can then be downloaded into multiple instruments.
- When the PC is not connected to the instrument, the above GUI screens can be used to set up a virtual instrument. The setup file can then be saved to disk. Switching toView Menu then brings up a screen with the required front panel programming steps. This view can be printed out for use at the instrument site and to serve as a hard copy record.
Download Free Instrument Setup Software
Installation
Set User Account Control (UAC) of MS Windows to "Never notifiy me" so that Instrument Setup Software can create directories. The UAC change screen can be reached as follows:
- Under Windows 7, click on the Windows Start button in the lower left of the desktop and enter "UAC" in the search field.
- Under Windows 8, navigate to Control Panel, then to the "User Accounts and Family Safety" section, and click on "Change User Account Control Settings."
- Under Windows 10, click on the Windows Start button in the lower left of the desktop, then on "Settings", and enter "UAC" in the search field.
- Reboot your computer for the changed UAC setting to take effect.
RJ11-to-DB9 cable with rear view of DB9 connector to PC
RS232 cable, meter to PC, P/N CBL01
Laureate 1/8 DIN Laureate instruments must be equipped with a serial communications board and be connected to the computer via a serial communications cable. The connection can be via RS232, RS485, USB or Ethernet. Following setup, the serial communications board may be removed from the instrument if desired. The wiring of the RS232 cable is illustrated above with end views of the two connectors.
Laureate LT Series transmitters come standard with a 3-wire serial interface, which can be jumpered for RS232 or RS485.
Laureate LTE Series transmitters come standard with an Ethernet interface.
Meter Setup Screens
Click on any of the reduced screens below for a full-size screen view, then click on the Back button of your browser to return to this page. The screens examples below are for a fully-loaded Series 2 Digital Panel Meter (DPM), which is connected to the PC via RS232. If the meter is a Series 1 meter (pre-2007), this is sensed by the software, and somewhat different screens are brought up. Please see Series 1 setup screens.
Welcome Screen
From the computer desktop, click on Start > Programs > IS2 > IS2. Or click on the IS icon on your desktop. This splash screen will be displayed for three seconds. The software revision number is in the lower right.
Communications Selection Screen
Specify your desired communication protocol and the serial communications bus type, which should match the jumper setup of the instrument. Select None if the PC is not connected to the instrument.
Establish Communications Screen
If you selected RS-232, you will be asked to specify the PC Com Port and Baud Rate, which should match the jumper setup of the instrument. Click on Establish. With the right settings, the Communications Established field will light up in green, and the Meter Type will be recognized. If so, click onMain Menu.
Main Menu Screen
Click on File > Default Setup to retrieve the default setup file from disk for your type of meter. Click on File > Open Setupto retrieve a previously saved setup file from disk or on File > Save Setup to save your edited setup file to disk. Click onDPM > Get Setup to retrieve the setup file from your meter or on DPM > Put Setup to download your edited setup file into the meter.
DPM Input + Display Setup Screen
From the Main Menu, click on View > Setup, then on theInput+Display tab. You can now specify the meter hardware, signal type, display mode, and functions of control inputs A and B. Clicking on any item brings up a pull-down menu with the available choices.
DPM Scaling Setup Screen
Click on the Scaling tab, which provides three scaling methods to relate the signal to the displayed reading: 1) Scale and Offset method, 2) Coordinates of two points method, and 3) Reading Coordinates of Two Points method. The last method uses actual high and low signals, and the computer will prompt you.
DPM Filter Setup Screen
Click on the Filter tab, which allows you to specify the digital filter time constant (if any), the adaptive filter threshold, and whether Peak / Valley values are filtered or unfiltered. As for all setup screens, clicking on the F1 key while an item is highlighted brings up a Help screen for that item, as illustrated.
DPM Relay Alarms Setup Screen
Click on the Relay Alarms tab, which allows you to set up Alarms 1 and 2 for the optional dual relay output board. Clicking on any of the four numeric fields changes these to green and brings up a special field to enter the desired numeric value, which is tied to the displayed reading.
DPM Communications Setup Screen
Click on the Communications tab so set up serial communications. In particular, you can special the Serial Protocol and the meter address if multiple meters are to be addressed on the same serial data line.
DPM Analog Output Setup Screen
Click on the Analog Out tab so set up the optional analog output board. Three output ranges are selectable, the endpoints of which can be tied to user-specified High and Low readings.
DPM Lockouts Setup Screen
Click on the Lockouts tab to check off menu items which will no longer be accessible from the front panel of the meter. This will simplify meter operation and prevent unintended setup changes.
Meter Setup Utilities
DPM Front Panel Setup Screen
As an aid to programming the meter from the front panel when a serial connection is not available, you can return to the Main Menu and click on View > Menu. The required sequence of front panel screens will then be displayed. Click on any step in the sequence for the meaning of each digit, as illustrated for the FILtEr step. For a hardcopy, simply press on Print.
DPM Jumper Setup Screen
Specify your desired communication protocol and the serial communications bus type, which should match the jumper setup of the instrument. Select None if the PC is not connected to the instrument.
DPM Jumper Setup Screens
Click on any of the displayed plug-in boards, and you will be presented with the jumper positions and electrical connections for your selected board. This minimizes the need to refer to the printed manual.
DPM Commands Screen
This page allows you set up external input, serial communications, an analog output proportional to the display (optional), and lockouts for Laureate digital counters. The grayed out area at the top right of the screen applies to Laureate remote displays.
Graphical Output Screens (not available with Ethernet)
From the Main Menu, click on Readings if your PC is connected to the meter. A pull-down menu then offers three choices: List, Plot and Graph.
- List presents the latest readings in a 20-row by 10-column table. Press Pause at any time to freeze the display. This is one method to capture peak readings.
- Plot generates a plot of readings vs. time in seconds. It effectively turns the DPM-PC combination into a printing digital oscilloscope.
- Graph generates a histogram where the horizontal axis is the reading and the vertical axis is the number of occurrences of readings. The display continually resizes itself as the number of readings increases.
DPM Calibration Screens
Click on the Scaling tab, which provides three scalClick on the Scaling tab, which provides three scaling methods to relate the signal to the displayed reading: 1) Scale and Offset method, 2) Coordinates of two points method, and 3) Reading Coordinates of Two Points method. The last method uses actual high and low signals, and the computer will prompt you.
Frequency Meter Calibration Screen
Calibration of the quartz crystal of the Laureate frequency meter requires the input of a known frequency from a calibrator. Apply the frequency, then enter the frequency in Hertz. Calibration will be automatic, with storage of the calibration factor stored in non-volatile memory.
Dimensions
Dimensioned CAD assembly drawings in EPRT, STEP, x_t, .dwg, pdf file formats: Laureate-transmitter-case.zip (zipping prevents browser from opening CAD files as text files).
| Controlling 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 | |
 |
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 | |
 |
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 | |
 |
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 | |
 |
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. |
CAL-Digital
Certificate of Calibration
$65.00
CBL02
USB-to-RS232 Adapter Cable
$47.00
CBL04
RS232 Cable for LT Transmitters
$47.00CBL12
12-foot Power Cable
$47.00CBL6
6-foot Power Cable
$41.00What Is the LT DIN Rail Transmitter for Ratio, Product, Sum, or Difference of 2 Rates or Totals?
Some applications don't just need a single flow rate or speed measurement — they need to know how two of them relate to each other. This variant of the LT DIN Rail Transmitter takes two independently scalable pulse input channels and combines them arithmetically — as a sum, difference, product, ratio, or draw — before converting the result into an isolated 4-20 mA analog output and digital serial data.
The Five Arithmetic Functions
The Extended counter main board makes five combinations of channels A and B available, applicable to scaled rates, scaled totals, square-root-extracted rates, or custom-curve-linearized values alike:
- Sum (A+B) — adding two flows for a combined total flow, or adding parts counted on two conveyor belts.
- Difference (A-B) — subtracting outflow from inflow for net flow, or subtracting reject parts from total parts produced.
- Product (AxB) — multiplying two rates together, such as computing horsepower as the product of torque and RPM.
- Ratio (A/B) — comparing two flow rates, two roller or gear speeds, or two batch totals being mixed.
- Draw (A/B-1) — measuring the elongation of material passing between rollers, or monitoring roller speed variation used for tensioning.
Named Applications
- Controlling the Mixing Ratio of Two Fluids — transmitting and alarming the A/B flow rate ratio of two gas or liquid inputs, typically sensed by turbine flow meters, keeps a continuous mixing process at a predetermined ratio; the same ratio can also be applied to totalized rate for delivered volume.
- Comparing Fluid Inflow and Outflow — the ratio of a tank's inflow and outflow rates indicates whether it's net filling or emptying; the same transmitter can also report net inflow/outflow in flow units or totalized volume, with either alarmed via the dual relay board.
- Controlling Coating Thickness on a Film — Channel A measures coating material flow rate while Channel B measures film speed from a proximity switch; transmitting and alarming the A/B ratio keeps coating thickness even as film speed varies.
- Synchronizing Conveyor Line Speeds — proximity switches sensing gear teeth or drive wheel spokes on two conveyor lines let the transmitter report a speed ratio, so line speeds can be adjusted to keep material arriving at work stations exactly when needed.
- Measuring Draw for Elongation — the draw function (A/B-1) indicates the elongation of film compressed between rollers, film shrinkage, or the RPM difference of rollers whose speed is varied to maintain tension; the transmitter's high resolution suits comparing rates that are close to each other.
Custom Curve Linearization for Nonlinear Inputs
The Extended main board also supports custom curve linearization using up to 180 user-entered data points, processed into spline-fit segments — useful when either input channel's transducer output isn't linear, such as a turbine flow meter that behaves nonlinearly at low flow, before the arithmetic function is applied.
Conclusion
The LT DIN Rail Transmitter for ratio, product, sum, or difference of two rates or totals gives a panel builder a way to monitor and control the relationship between two pulse-based signals directly, rather than tracking each one separately and doing the comparison elsewhere. Whether the application is mixing two fluids in a fixed ratio, comparing tank inflow to outflow, holding coating thickness steady, synchronizing conveyor lines, or measuring material elongation between rollers, its five arithmetic functions and optional custom curve linearization make it a purpose-built fit for two-channel process comparison.
Ratio, Product, Sum, or Difference Transmitter Frequently Asked Questions
Why use the ratio function instead of just monitoring both flow rates separately and comparing them manually?
Computing the ratio directly in the transmitter provides a single, continuously updated value suited to automated alarming and control — a mixing process can react to ratio drift in real time rather than relying on an operator or external system to compare two separate readings and calculate the relationship themselves.
Can the arithmetic functions be applied to totals as well as rates?
Yes — all five functions (A+B, A-B, AxB, A/B, A/B-1) can be applied to scaled totals just as they can to scaled rates, which is what makes it possible to compare two batch totals being mixed, not just their instantaneous flow rates.
What's the difference between using the ratio function and the draw function for two similar speeds?
Ratio (A/B) reports the raw proportion between the two channels, while draw (A/B-1) reports that same relationship shifted so that equal speeds read as zero — making small deviations from a 1:1 relationship, like the slight elongation of film between rollers, much easier to read directly rather than parsing a ratio value close to 1.0.
Why does the mixing ratio application recommend a turbine flow meter specifically?
Turbine flow meters output a pulse train at a frequency proportional to flow rate, which matches directly with this transmitter's pulse-counting input channels; other flow-sensing technologies that don't produce a proportional pulse output would need additional signal conditioning before they could feed this transmitter's ratio function.
Can this transmitter alarm on the computed ratio itself, not just the two individual rates?
Yes — the computed arithmetic result (sum, difference, product, ratio, or draw) can be sent to the dual relay board for alarming, so a ratio drifting outside an acceptable band can trigger an alarm or control action directly from the combined value.
Does custom curve linearization need to be applied to both channels, or can it apply to just one?
Linearization is applied per input channel based on that channel's own transducer characteristics, so it's entirely possible to linearize one channel (say, a nonlinear turbine meter) while leaving the other channel's linear-output sensor unlinearized, before the two are combined arithmetically.
What's the benefit of high resolution specifically for the draw/elongation application?
When comparing two rates that are close to each other — like roller speeds with only slight tension-driven variation — a small absolute difference represents a large fraction of the meaningful signal; high resolution ensures that small, meaningful variation isn't lost in measurement noise or rounding.
Can this transmitter compare a rate on one channel to a total on the other?
The arithmetic functions are designed to combine two values of the same type — rate with rate, or total with total — rather than mixing a rate and a total directly in one arithmetic operation, since the units wouldn't otherwise be comparable.
Can multiple ratio/sum/difference transmitters be networked together?
Yes — up to 30 LT Transmitters and/or Digital Panel Meters can be daisy-chained on RS485 for LAN integration, or an LTE series Ethernet transmitter can be used instead for a direct Ethernet connection.
Ratio, Product, Sum, or Difference Transmitter Questions From the Field
My mixing ratio reads correctly at high flow but drifts at low flow — what's the likely cause?
Low-flow drift in a ratio calculation often traces back to one channel's flow meter (commonly a turbine meter) behaving nonlinearly at low flow rather than a fault in the ratio calculation itself; applying custom curve linearization to the affected channel is the standard fix.
My inflow/outflow comparison shows a nonzero net flow even though the tank level looks stable — why?
A small nonzero net flow reading with a visually stable tank level can simply reflect measurement resolution and normal sensor tolerance rather than an actual leak or fault; comparing the reported net flow rate against the tank's actual level trend over a longer period helps distinguish real net flow from measurement noise.
My coating thickness ratio alarm triggers during normal film speed changes — how is that addressed?
This usually points to the alarm deadband or response timing being too tight for the rate at which film speed changes during normal operation; widening the alarm deadband or adding a short delay before the alarm triggers typically resolves nuisance trips during expected speed transitions.
My two conveyor lines drift out of sync even though the speed ratio reads correctly — what should I check?
If the ratio reading itself is accurate, the drift is more likely in the downstream control loop adjusting line speed based on that ratio rather than in the measurement; verifying the control system is actually acting on the transmitted ratio value with appropriate responsiveness is the next troubleshooting step.
My draw reading is noisy even though the two roller speeds seem stable — why?
Because draw compares two rates that are intentionally close to each other, any noise on either channel is amplified in the relative comparison; checking each channel's raw signal quality independently (proximity switch alignment, cable shielding) before assuming a computation fault is the standard first step.
Can noise on just one of the two input channels throw off an arithmetic result even if the other channel is clean?
Yes — since the arithmetic functions combine both channels, noise or instability on either single channel propagates into the combined result; isolating and testing each channel independently is the standard way to determine which channel is actually the source of an unstable arithmetic reading.
My totalized ratio doesn't match what I calculate manually from the two individual totals — what should I check?
Confirming both channels are scaled to consistent units before the ratio is computed is the first step, since a ratio calculated from totals in mismatched units (like gallons on one channel and liters on the other) will produce a result that doesn't match a manual calculation done in a single consistent unit.
