Laurel Electronics QLS Quad Output 4-20 mA Current Loop - Datasheet - Manual

LAUREL ELECTRONICS INC., 3183-G Airway Ave., Costa Mesa, CA 92626, USA • Tel 714-434-6131 • www.laurels.com 1
LAUREL
ELECTRONICS, INC.
QLS Quad Output 4-20 mA Current Loop
Splitter / Retransmitter
Features
• Accepts a 4-20 mA, 1-5V, 0-5V or 0-10V input signal.
• Drives four (4) independent 4-20 mA outputs proportional to input
• Outputs can share a common ground
• Grounds of input and outputs can differ by up to ±10V
• Opening any output loop does not affect the other loops
• ±10% zero and span fine adjustments for each output loop
• Loop current test point for each output, where 200 mV = 20 mA
• Indicator LED for each connected output
• Powered by 85-264 Vac (Model QLS-1) or 10-48 Vdc (Model QLS-2)
• Powers a 2- or 3-wire input transmitter at 24V with up to 30 mA
• 22.5 mm (0.9") wide case snaps to 35 mm DIN rail
• Weighs only 159 g (5.6 oz)
Problems with Current Loop Loads in Series
Not so good: A single 4-20 mA loop from a sensor is connector to a panel meter, a control valve, a recorder and a PLC in series. If
the loop opens, all devices in the loop fail.
1. All devices in the loop cannot share a common ground, but
must be electrically floating. This is often not possible.
2. When any device in a loop is removed, fails or if a wiring fault
occurs, all other devices in the loop loose their 4-20 mA signal.
3. The transmitter voltage compliance limit may be exceeded,
since the voltage drops across loads in series are additive.
4. The 4-20 mA signal to each load device cannot be individually
adjusted for calibration purposes.
The QLS Loop Splitter / Retransmitter Solution
Much better: Four independent 4-20 mA loops with ±10V common mode isolation. If any of the output loops opens, only a single
device is affected. The output loops can share a common ground.
1. Up to four (4) independently adjustable 4-20 mA outputs are
generated from a single input, which can be 4-20 mA, 1-5V,
0-5V or 0-10V, as selected by jumpers.
2. If any device in an output loop is removed from a loop or fails,
or if a wiring fault occurs in any loop, the other loops continue
to operate properly.
3. The outputs can share a common ground. The input and
outputs are mutually isolated to ±10V by means of active
circuitry to accommodate differences in local grounds with
normal industrial grounding practices.
4. Each loop only drives a single load, thus avoiding voltage
compliance problems.
5. ±10% of zero and span adjustment are provided for each out-
put loop to allow for independent loop calibration.
6. Diagnostics for each output loop are provided by a yellow LED
lamp to indicate loop continuity and by a test point across a
10Ω series resistor, where 200 mV corresponds to 20 mA. The
test point allows a multimeter to measure the loop current
without breaking the loop.
7. Power for the loop splitter can be 85-264 Vac (Model QLS-1)
or low voltage 10-48 Vdc or 12-32 Vac (Model QLS-2). An
excitation output is provided on the signal input side to a drive
a 2- or 3-wire transmitter at 24 Vdc and up to 30 mA.