Laurel Electronics LT: 4-20 mA Current Loop Transmitter for Resistance Input in Ohms - Manual

LAUREL ELECTRONICS INC., 3183-G Airway Ave., Costa Mesa, CA 92626, USA • Tel 714-434-6131 • www.laurels.com 1
LAUREL
ELECTRONICS, INC.
4-20 mA Current Loop Transmitter
for Resistance Input in Ohms
Features
• Five precalibrated resistance input ranges from 20.000 Ω to 200.00 kΩ
• Optional fixed 2.0000 MΩ range
• Exceptional accuracy and repeatability
• 1 mΩ resolution on 20 Ω scale
• 2, 3 or 4-wire connection with lead resistance compensation
• DIN rail mount housing only 22.5 mm wide, detachable screw-clamp connectors
• 4-20 mA or 0-10V transmitter output, jumper selectable, isolated
• Analog output resolution 0.0015% of span (16 bits), accuracy ±0.02% of span
• RS232 or RS485 serial data output, half or full duplex, isolated
• Modbus RTU, Modbus ASCII or Laurel ASCII protocol
• Dual solid state relays for binning, alarm or control, isolated
• Universal AC power, 85-264 Vac, or low voltage power, 10-48 Vdc or 12-32 Vac
Description
The Laureate Resistance Transmitter is factory calibrated
for five jumper selectable resistance ranges from 20Ω to 200 kΩ.
Accuracy is an exceptional 0.01% of full scale ±2 counts. Reso-
lution is one part in 20,000. In the 20Ω range, resolution is 1 mΩ,
making the transmitter suitable for contact resistance and con-
ductance measurements.
Transmitter connections can be via 2, 3 or 4 wires. With 4-wire
hookup, 2 wires are used for excitation and two separate wires
are used to sense the voltage across the resistance to be
measured, thereby eliminating any lead resistance effects. With
3-wire hookup, the transmitter senses the combined voltage drop
across the RTD plus two excitation leads. It also senses the
voltage drop across one excitation lead, and then subtracts twice
this voltage from the combined total. This technique effectively
subtracts the lead resistance if the excitation leads are the same.
All resistance ranges are digitally calibrated at the factory, with
calibration factors stored in EEPROM on the signal conditioner
board. This allows ranges and signal conditioner boards to be
changed in the field without recalibrating the transmitter. If
desired, the transmitter can easily be calibrated using external
standards plus scale and offset in software.
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.
Open sensor indication is standard and may be set up to indi-
cate either upscale or downscale. Excitation is provided by the
transmitter.
Custom curve linearization, available with the Extended
version, makes this transmitter ideal for use with transducers
whose output is a changing resistance.
Standard features of Laureate transmitters include:
• 4-20 mA, 0-20 mA or 0-10V 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.
The supply can drive 20 mA into a 500Ω (or lower) load for
10V compliance, or 10V into a 5 kΩ (or higher) load for 2 mA
compliance.
• Serial communications output, isolated. User selectable
RS232 or RS485, half or full duplex. 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
allows up to 31 Laureate devices to be addressed on the
same RS485 data line. It is simpler than the Modbus protocol
and is recommended when all devices are Laureates.
• Dual solid state relays, isolated. Available for local alarm or
control. Rated 120 mA at 130 Vac or 170 Vdc.
• 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).