QLS Quad Output 4-20 mA Current Loop Splitter / Retransmitter

Splits 1 input signal into 4 independent 4-20 mA current loops with ± 10V common mode isolation between input & outputs.
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Key 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 up to ±10V.
  • Opening any output loop does not affect 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 goes to panel meters, 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.

5.
There are not diagnostics for the current to each load.

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 spand adjustment is provided for each output loop to allow for independent loop calibration.

6.

Diagnostics for each output loop are provied 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.