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DC Input Field Configurable Limit Alarms


DC Input Field Configurable Limit Alarms | SMLA-SERIES

DC Input Field Configurable Limit Alarms

See All Models Below

  • SMLA-1 (Single Trip, DPDT, 5A) SMLA-2 (Single/Dual Trip, 2 SPDT, 5A)
  • Field Configurable Input Ranges for DC Voltage and Current
  • Exclusive “Dynamic Deadband” Prevents False Trips
  • Provides Relay Contact Closures at a Preset DC Input Level
  • Programmable HI or LO Setpoints
  • Failsafe/Latching Operation
  • Selectable 120/240 Vac Input Power
Process Measurement and Control Instruments - View related products


SMLA-1 single setpoint and SMLA-2 dual setpoint limit alarms offer flexible, wide-ranging DC input capability. Voltage spans from 10 mV to 200V and current spans from 1 mA to 100 mA can be field configured. Bipolar inputs are also accepted. Both models offer configurable latching, failsafe and HI/LO operation. The SMLA-1 and SMLA-2 also include 0.25% to 50% adjustable deadbands and selectable 120/240 Vac input power.

Models SMLA-1 and SMLA-2 are equipped with a dual function diagnostic LED. The green center LED indicates line power and input signal status. Active line power is indicated by an illuminated LED. If the center LED is off, check line power and the wiring connection. If the input signal is above 100% full scale, the LED will flash at approximately 8 Hz. Below 0%, the flash rate is approximately 4 Hz.

The single setpoint SMLA-1 and the dual setpoint SMLA-2 provide the following relay outputs: SMLA-1 Single Trip (DPDT, 5A); SMLA-2 Single/Dual Trip (2 SPDT, 5A). Setpoints are top accessed multi-turn potentiometers.

The field configurable SMLA-1 and SMLA-2 limit alarm setpoints can be configured for HI, LO, latching or failsafe trip operation. Non-latching HI and LO setpoints have respective HI and LO deadbands. In a tripped condition, the setpoint is exceeded and the appropriate red LED will illuminate. The trip will reset only when the process falls below the HI deadband or rises above the LO deadband. To reset a latched setpoint the signal must be in the safe region and the line power turned off for at least 5 seconds. For proper deadband operation, a HI setpoint must always be set above a LO setpoint.

In failsafe operation, the relay is energized when the process is below the HI setpoint or above the LO setpoint (opposite for nonfailsafe). In the failsafe mode, the relays go to the tripped condition when the power fails.

The input must remain beyond the setpoint for 100 milliseconds, uninterrupted, to qualify as a valid trip condition. Likewise, the input must fall outside the deadband and remain there for 100 milliseconds to return the alarm to an untripped condition. This effectively results in a “dynamic deadband” - based on time - in addition to the normal deadband.

Voltage Input (Unipolar or Bipolar):

    Range: 10 mV, 20 mV, 50 mV, 100 mV, 200 mV, 500 mV, 1V, 2V, 5V, 10V, 20V, 50V, 100V, 200V (dip-switch selectable)
    Impedance: >100 kΩ
    Overvoltage: 400V max
Current Input (Unipolar or Bipolar):
    Range: 1 mA, 2 mA, 5 mA, 10 mA, 20 mA, 50 mA, 100 mA (dip-switch selectable)
    Impedance: 20 Ω typical
    Overcurrent: 200 mA max
    Overvoltage: 60 Vdc
Common Mode (Input to Ground): 1000 Vdc max
LED Indications:
    Input Range (Green):
      >100% Input: 8 Hz flash
      <0% Input: 4 Hz flash
    Setpoint (Red):
      Tripped: Solid red
      Safe: Off
Limit Differential (Deadband):
    >50 mV/5 mA: 0.25% to 50% of span
    <50 mV/5 mA: 1% to 50% of span
Response Time:
    Dynamic Deadband: Relay status will change when proper setpoint/process condition exists uninterrupted
    for 100 msec
    Normal Mode (Analog Filtering): <250 msec, (10 to 90%)
    Effectivity: Setpoints are adjustable over 100% of the selected input span
    Repeatability (Constant Temp):
      >50 mV/5 mA: 0.1% of full scale
      <50 mV/5 mA: 0.2% of full scale
    Line Voltage: ±0.01%/% max
    Temperature: ±0.05% of full scale/°C max
Common Mode Rejection: DC to 60 Hz: 120 dB
Isolation: 1000 Vdc between contacts, input and power
ESD Susceptibility: Meets IEC 801-2, Level 2 (4 KV)
    Operating: 15 to 95 %RH @ 45°C (113°F)
    Soak: 90 %RH for 24 hours @ 65°C (149°F)
Temperature Range:
    Operating: 0 to 60°C (32 to 140°F)
    Storage: -15 to 70°C (5 to 158°F)
Power: 120/240 Vac ± 10%, 50 to 60 Hz selectable, 2 W typical, 5 W max
Relay Contacts:
    SMLA-1: DPDT (2 Form C)
    SMLA-2: 1 SPDT (1 Form C) per setpoint
    Current Rating (Resistive): 120 Vac: 5A; 240 Vac: 2A; 28 Vdc: 5A (external relay contact protection
    is required for use with inductive loads)
    Material: Silver-Cadmium Oxide
    Electrical Life: 105 operations at rated load
    Mechanical Life: 107 operations
Latch Reset Time: 5 seconds
    SMLA-1: 209 g (0.46 lb)
    SMLA-2: 282 g (0.62 lb)
(Specify Model Number)
Part Number/Desc.
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Single setpoint DC input field configurable limit alarm
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Dual setpoint DC input field configurable limit alarm
Consult Sales  
11-pin socket, DIN rail mount
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11-pin socket, surface mount
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35 mm DIN rail, 2 m (6.6') length
Consult Sales  
Retaining spring (secures limit alarm module into DIN rail or surface mount socket)
All prices on this site are shown in Taiwan Dollars.
Note: Comes complete with operator’s manual.
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