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DC Input Field Configurable Limit Alarms
TRODEKS Engineering | Thermocouples, Pressure Transducers, Flow Meters, PID Controllers
  • 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
 Manuals (contact with email : [email protected])


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

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

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

The field configurable SMLA-1 and SMLA-2 limit alarmsetpoints can be configured for HI, LO, latching or failsafetrip operation. Non-latching HI and LO setpoints haverespective HI and LO deadbands. In a tripped condition,the setpoint is exceeded and the appropriate red LED willilluminate. The trip will reset only when the process fallsbelow the HI deadband or rises above the LO deadband.To reset a latched setpoint the signal must be in the saferegion and the line power turned off for at least 5 seconds.For proper deadband operation, a HI setpoint must alwaysbe set above a LO setpoint.

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

The input must remain beyond the setpoint for100 milliseconds, uninterrupted, to qualify as a validtrip condition. Likewise, the input must fall outside thedeadband and remain there for 100 milliseconds to returnthe alarm to an untripped condition. This effectively resultsin a “dynamic deadband” - based on time - in addition tothe 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 propersetpoint/process condition exists uninterrupted
    for 100 msec
    Normal Mode (Analog Filtering): <250 msec, (10 to 90%)
    Effectivity: Setpoints are adjustable over 100% of theselected 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)
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