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LTA-WM 4-20 mA Current Transmitter
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Standard Features
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Description The Laureate LTA-WM 4-20 mA output, 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 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. 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 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 at up to 50 or 60 conversions per second while integrating the signal over a full power line cycle is provided by Concurrent Slope (Pat 5,262,780) analog-to-digital conversion. High read rate is 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. The internal digital readings and analog output can be separately selected to be either unfiltered or filtered.
Three analog transmitter settings are jumper selectable: 4-20 mA, 0-20 mA or 0-10V. All selections provide 16-bit (0.0015%) resolution of output span and 0.02% output accuracy. The output tracks the reading from -99,999 to +99,999 counts that would be transmitted digitally. For DC signals, this reading has a rated accuracy of ±0.01% of full scale input and can be scaled in software. Output isolation from signal and power grounds eliminates potential ground loop problems. The supply can drive 20 mA into a 500 ohm (or lower) load for 10V compliance, or 10V into a 5K ohm (or higher) load for 2 mA compliance. Standard features of Model LTA-WM include:
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). |
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Load Cell
Transmitter Connections |
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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. | |
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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. | |
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For large scales, up to four 350 ohm load cells in parallel can be powered by a single Laureate transmitter at 10V, 120 mA excitation. The excitation and sense points of the four bridges are connected in parallel through a summing box. | |
Specifications
LTA-WM 4-20 mA Transmitter
for
Load Cell or Microvolt Input
| Analog Input | Range | Resolution | Input Ohms |
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Load Cell Input |
±20.000 mV ±50.0000 V ±100.00 V ±250.00 V ±500.00 V |
-99,999 to +99,999 zero adjust. 0 to ±99,999 span adjust. |
1 Gohm |
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Microvolt Input |
±20.000 mV ±50.0000 V ±100.00 V ±250.00 V ±500.00 V |
1 µV 2.5 µV 5.0 µV 12.5 µV 25 µV |
1 Gohm |
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Input Resolution Input Accuracy Update Rate, Max Max Applied Voltage |
16 bits (65,536 steps) ±0.01% of full scale ± 2 counts 50/sec at 50 Hz, 60/sec at 60 Hz. 100 V |
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| Transducer Excitation Output (standard) | |||
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Output levels Output isolation |
5V@100 mA, 10 @120 mA, 24V@50 mA (jumper
selectable) 50V from signal ground |
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| Analog Output (standard) | |||
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Output Levels Compliance, 4-20 mA Compliance, 0-10V Output Resolution Output Accuracy Output Isolation |
4-20 mA, 0-20 mA, 0-10 Vdc (jumper selectable) 10V ( 0-500 ohm load ) 2 mA ( 5 kOhm load or higher) 16 bit DAC ±0.02% of output span plus conversion accuracy 250V rms working, 2.3 kV rms per 1 minute test |
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| Dual Relay Output (standard) | |||
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Relay Type Load rating |
Two solid state relays, SPST, normally open,
Form A 120 mA at 130 Vac or 170 Vdc, 28 ohms in series |
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| Serial Communications (standard) | |||
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Signal Types Data Rates Output Isolation Serial Protocols Modbus Modes Modbus Compliance Digital Addressing |
RS232 (default) or RS485 (half or full duplex) 300, 600, 1200, 2400, 4800, 9600, 19200 baud 250V rms working, 2.3 kV rms per 1 min test Modbus RTU, Modbus ASCII, Laurel ASCII RTU or ASCII Modbus over Serial Line Specification V1.0 (2002) 247 Modbus addresses. Up to 32 devices on an RS485 line w/o a repeater. |
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| Power Input | |||
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Standard power Low power option Power frequency Power Isolation |
95-240 Vac ±10% or 90-300 Vdc (DC operation not UL approved) 10-48 Vdc or 12-30 Vac DC or 47-63 Hz 250V rms working, 2.3 kV rms per 1 min test |
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| Mechanical | |||
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Case Dimensions Case Mounting Electrical Connections |
120 x 101 x 22.5 mm 35 mm rail per DIN EN 50022 Detachable screw-clamp plugs |
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| Environmental | |||
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Operating Temp. Storage Temp. Relative Humidity |
0°C to
70°C -40°C to 85°C 95% at 40°C, non-condensing |
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Pinout
LTA-WM 4-20 mA Transmitter
for
Load Cell or Microvolt Input
Ordering
Guide
LTA-WM 4-20 mA Transmitter
for
Load Cell or Microvolt Input
Click
on the radio buttons to build a model number with pricing.
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