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.
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.
|Signal Input & Excitation|
|Signal Type||4-20 mA, 1-5V, 0-5V, 0-10V (jumper selectable)|
|Input Resistance||50Ω for 4-20 mA, 412kΩ for 1-5V, 464kΩ for 0-5V, 935kΩ for 0-10V|
|Transducer Excitation||24 Vdc output, 30 mA max|
|Number of Outputs||4|
|Signal Type||4-20 mA|
|Signal Ground||Same signal ground for input and outputs|
|Common Mode Voltage||Remote signal grounds can be up to ± 10V from local signal ground|
|Zero & Span Adjustments||± 10% for each output with 25-turn potentiometers|
|Isolation Power to Signals||264 Vac|
|Voltage Compliance||12V (600Ω per loop at 20 mA)|
|Load Regulation||± 0.005% of span from 0Ω to 600Ω|
|Accuracy||± 0.02% max span error at 23°C|
|Zero Tempco||± 0.1 µA/°C typical, ± 0.2 µA/°C max|
|Span Tempco||± 10 ppm/°C (0.16 µA/°C) typical, ± 20 ppm/°C (0.32 µA/°C) max|
|AC Rejection||90 dB from DC to 60 Hz|
|Response Speed||2 ms risetime, 7 ms settling time to 0.1% of final value|
|Loop Current Sense||10Ω ± 0.5% series resistor. Generates 200 mV at 20 mA|
|Loop Continuity Indication||Yellow LED lamp per loop, brightness proportional to current.|
|Model QLS-1||85-264 Vac or 90-300 Vdc (DC operation not ETLapproved)|
|Model QLS-2||10-48 Vdc or 12-32 Vac|
|Power Frequency||DC or 47-63 Hz|
|Power Isolation||250V AC working, 1.0 kV AC for 60 sec, 1.7 kV DC for 2 sec|
|Power Consumption||3.5 W max, all loops delivering 20 mA|
|Power On Indication||Green LED lamp|
|Mounting||35 mm rail per DIN EN 50022|
|Dimensions||22.5 x 103 x 128 mm (0.9" x 4.1" x 5.0") W x H x D|
|Weight||140 g (5 oz)|
|Connectors||Detachable plug-in screw-clamp connectors|
|Wire Size||28-12 AWG, 2.5 sq. mm max|
|Operating Temperature||-40°C to 70°C|
|Storage Temperature||-40°C to 85°C|
|Relative Humidity||95% at 40°C, non-condensing|
|Cooling Required||Mount transmitters with ventilation holes at top and bottom. Leave 6 mm (1/4") between transmitters, or force air with a fan.|
Galvanic & Active Isolation: A single input current loop is split into four independent output loops I1, I2, I3 and I4 by four current generators. The input and output signals are galvanically isolated from power and earth grounds by up to 264 Vac. Active circuitry allows a common mode voltage up to ±10V between Local Signal Ground (on pins 1) and the Remote Grounds. Each common mode voltages, labeled CMV1 to CMV4 in the diagram, reflects the actual voltage difference between Local Signal Ground and the Remote Ground. Such differences can be caused by current flows in the factory.
Floating loads: Any output load R that is floating (not connected to Earth Ground or a Local Ground) can be connected between current output (Pin 1) and current return (Pin 2). Current return is internally tied to Signal Ground, which can be floating or be connected to Earth Ground.
Grounded loads: Any output load R can be connected to a Local Ground instead of current return. The Remote Grounds can each be different, but can only differ from Signal Ground by a safe common mode voltage CMV. Signal Ground should be tied to Earth Ground to minimize noise pickup.
Input-output isolation: If a load R is grounded to a Local Ground, the available common mode voltage CMV is limited on the positive side by the unit's internal power supply and on the negative side by the 600 mW power dissipation limit of an output transistor. The above diagram shows allowable CMV as a function of output load resistance R. For example, with a 250Ω load, CMV can range from -13V to +17V. With a 500Ω load, CMV can range from -18V to +12V. The unit will not work correctly if CMV limits are exceeded or the load resistance is greater than 600Ω.