4-20 mA & Serial Data Transmitter for Load Cell & Microvolt Signals

Sensitivity to 1 µV. Ideal for load cells & pressure transducers. DIN rail mounted, digitally programmable. Includes two relays for alarm or control.

 load cell transmitter

Features

  • 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 TDM ASCII protocol, isolated
  • Dual 120 mA solid state relays for alarm or control, isolated
  • 20, 50, 100, 250 and 500 mV full-scale input ranges
  • 4 or 6-wire hookup to avoid power supply and lead resistance effects
  • Digital span adjust from 0 to ±99,999, zero adjust from -99,999 to +99,999
  • Analog output resolution 0.0015% of span (16 bits), accuracy ±0.02% of span
  • 10V excitation supply for up to four 350-ohm load cells in parallel
  • Universal 85-264 Vac / 90-300 Vdc or 10-48 Vdc / 12-32 Vac power
  • Custom curve linearization and rate from successive readings (optional)
Description

The load cell or microvolt input transmitter is designed for use with load cells, strain gauges and microvolt input signals where exceptional sensitivity and stability are required. A most sensitive full-scale input range ±20.000 mV can be scaled internally to ±99,999 counts. The selected input range for the full 0-20 mA output span can be as wide as ±99,999 counts or as narrow as 150 counts, limited only by considerations of electrical noise and time constants of the programmable moving average digital filter. The unit's serial data output is accurate to ±0.01% of reading ±2 counts in ratiometric load cell mode and ±0.01% of full scale in ±2 counts in absolute microvolt meter mode.

A built-in, isolated, 10V, 120 mA excitation supply can power up to four 350-ohm load cells in parallel. Load cell connection can be via 4 or 6 wires. With 4-wire load connection, the transmitter operates in a ratiometric mode to eliminate errors due to power supply variations. With 6-wire load connection, it also compensates for lead resistance, allowing long cable runs.

Fast read rate at up to 50 or 60 conversions per second while integrating the signal over a full power line cycle are ideal for peak or valley capture and for real-time computer interface and control.

Digital signal filtering modes are selectable for 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 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. An Auto setting selects the time constant selection based on signal noise.

Standard features of LT transmitters include:

  • 4-20 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 loop problems.
  • Serial communications output, RS232 or RS485 (half or full duplex), jumper selectable. Three protocols are user selectable: Modbus RTU, Modbus ASCII, or TDM ASCII. Modbus operation is fully compliant with Modbus Over Serial Line Specification V1.0 (2002). The TDM ASCII protocol is simpler than the Modbus protocol and is recommended when all devices are s.
  • 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 TDM'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 TDM (P/N CBL04).

Load Cell Transmitter Connections

4-wire load cell bridge connection of load cell transmitter In 4-wire connection, the excitation and sense lines are tied together. The transmitter can make ratiometric corrections for supply voltage variations, but does not compensate for variations in lead resistance. This connection is often used with short cable runs.
4-wire load cell bridge connection of load cell transmitter In 6-wire connection, the sense lines are separate from the excitation lines, thereby eliminating effects due to variations in lead resistance. This allows long cable runs in outdoor environments with temperature extremes.
Up to six 350-ohm load cell bridges connected in parallel to a load cell transmitter For large scales, up to four 350 ohm load cells can be powered by a single , whose excitation output is rated 120 mA at 10V. The excitation and sense points of the four bridges are connected in parallel. The load cell outputs will be averaged if the load cells have the same sensititivity in mV/V.
Specifications
Analog Input Range Scaling Input Ohms Error at 25°C
Load Cell Input ±20.000 mV -99,999 to +99,999
zero adjust.
0 to ±99,999
span adjust.
1 GΩ ±0.01% of rdg
± 2 cts
±50.0000 mV
±100.00 mV
±250.00 mV
±500.00 mV
Microvolt Input ±20.000 mV 1 µV 1 GΩ ±0.01% of FS
± 2 cts
±50.0000 mV 2.5 µV
±100.00 mV 5.0 µV
±250.00 mV 12.5 µV
±500.00 mV 25 µV
Reading Resolution 16 bits (65,536 steps)
Reading Accuracy ±0.01% of reading ± 2 counts in ratiometric mode,
±0.01% of full scale ± 2 counts in absolute mode
Update Rate, Max 50/sec at 50 Hz, 60/sec at 60 Hz
Max applied voltage 100 V
Analog Output (standard)
Output Levels 4-20 mA, 0-20 mA, 0-10 Vdc, -10 to +10Vdc (user selectable)
Compliance, 4-20 mA 10V (0-500Ω load)
Compliance, 0-10V 2 mA (5 kΩ load or higher)
Output Resolution 16 bits (65,536 steps)
Output Accuracy 0.02% of output span plus conversion accuracy
Output Isolation 250V rms working, 2.3 kV rms per 1 minute test
Transducer Excitation Output (standard)
Output Levels 5V@100 mA, 10V @120 mA, 24V@50 mA (jumper selectable)
Output Isolation 50V from signal ground
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
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 TCP, Modbus RTU, Modbus ASCII, TDM ASCII
Modbus Compliance Modbus over Serial Line Specification V1.0 (2002)
Ethernet Connector RJ45 jack for 10/100 Base-T Ethernet cable
RS232/485 Connector Screw terminals for easy daisy chaining
Digital Addresses 247 for Modbus, 31 for TDM ASCII
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 2Watts
Mechanical
Dimensions 129 x 104 x 22.5 mm case
Mounting 35 mm rail per DIN EN 50022
Electrical Connections Plug-in screw-clamp connectors
Environmental
Operating Temp. 0°C to 55°C
Storage Temp. -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.
Pinout
 LT transmitter pinout

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