Laurel Electronics QLS Quad Output 4-20 mA Current Loop - Manual - Manual (Page 2)

- - 2 -
1. ORDERING GUIDE
QLS-1 Quad isolated output loop splitter/ retransmitter, 85-264 Vac power.
QLS-2 Quad isolated output loop splitter/ retransmitter, 10-48 Vdc or 12-32 Vac power.
3. PRODUCT DESCRIPTION
Model QLS sources up to four (4) independently adjustable 4-20 mA outputs from a single input,
which can be 4-20 mA, 1-5V, 0-5V or 0-10V, as selected by jumpers. The outputs can share a
common ground. The input and outputs are mutually isolated to +10V / -20V at 600 ohm load by
means of active circuitry to accommodate differences in local grounds. If any device in an output
loop is removed from the loop or fails, or if a wiring fault occurs, the other loops continue to
operate properly. Each loop only drives a single load, avoiding compliance problems.
Model QLS overcomes problems of simply placing loads in series in a single 4-20 mA loop. In
such a configuration, the devices in the loop cannot share a common ground, but must be
electrically floating, which is often not possible. When any device in a single loop is removed, fails
or if a wiring fault occurs, all other devices in the loop loose their 4-20 mA signal. The transmitter
voltage compliance limit may be exceeded, since the voltage drops across loads in series are
additive. Also, the 4-20 mA signal to each load device cannot be individually adjusted for
calibration purposes.
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.
Each output loop provides two potentiometers for ±10% fine adjustment of zero and span, a
yellow LED lamp to indicate loop continuity, and a current test point across a 10-ohm series
resistor, where 200 mV corresponds to 20 mA. This allows a multimeter to be used to measure
the loop current without breaking the loop.
4. RECEIVING & UNPACKING
Your QLS loop splitter / retransmitter was carefully tested and inspected prior to shipment. Should
the unit be damaged in shipment, notify the freight carrier immediately. Inspect the label on the
unit for the type of input power: QLS-1 for 85-264 Vac power, or QLS-2 for 10-48 Vdc or 12-32
Vac power. In the event the unit is not as ordered or is inoperable, return it to the place of
purchase for repair or replacement. Please include a description of the problem.