Thermocouple Input, Field Configurable Limit Alarm - Q126

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The ActionI/Q model Q126 is a DIN rail mount, thermocouple input limit alarm with input terminal cold junction compensation (cjc), dual setpoints and two contact closure outputs. The field configurable input and alarm functions offerflexible setpoint capability. There are up to six temperature ranges available for each thermocouple type to ensure accuracy and maximize setpoint resolution. A bipolar input switch is provided for temperature ranges below 0°C.  

Thanks to Action's exclusive TouchCAL Technology, the Q126 is configurable as a single or dual setpoint alarm, with HI or LO trips, upscale or downscale thermocouple burnout detection and failsafe or non-failsafe operation. Also included are adjustable deadbands (up to 100% of full scale input) for each setpoint and a universal AC power supply which accepts any voltage between 85 and 265VAC.

Touchcal Technology

Advances in microprocessor technology enable Action to simplify setpoint calibration. Using a push- button instead of potentiometers, improvements in calibration resolution and reliability are realized due to the elimination of the potentiometer's variability.

For calibration, the user simply inputs the signal level of the desired trip, then presses the push-button to store it in non-volatile memory. The dead band, or hysteresis, level is input next and is stored with another press of the button.

Diagnostic LEDs

The Q126 is equipped with three front panel LEDs. The first is a dual function LED labeled IN (INPUT) This green LED indicates AC power and input signal status. Active AC power is indicated by an Protecting the Integrity of Industrial Process Signals An Invensys Company illuminated LED. If this LED is off, check line power and wiring connection. If the input signal is 7% above or below the configured input range the green LED will flash at 8Hz or 4Hz, repectively.

Two red LEDs indicate the relay state for each setpoint. An illuminated red LED indicates a tripped condition.


The Q126 is equipped with two SPDT (form C) relays, rated at 120VAC or 28VDC at 5 amperes. Each of these relays is independently controlled by the field configurable setpoint and deadband. 


The field configurable Q126 limit alarm setpoints can be configured for HI or LO, failsafe or non-failsafe operation. Each of the setpoints has a respective HI or LO deadband. In a tripped condition, the setpoint is exceeded and the appropriate red LED will illuminate.

Dynamic Deadband

LSI circuitry in the Q126 prevents false trips by repeatedly sampling the input. 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.



  • Easy Field Configurable Input Ranges for J, K, N, C, T, R, S, E, and B Type Thermocouples

  • Touch CAL™ Technology for Easy Setpoint Calibration

  • Adjustable Setpoints Programmable HI or LO and Failsafe or Non- Failsafe

  • High Density DIN Rail Mounting

  • SnapLoc™ Plug-in Terminals for Low MTTR

  • LED Trip and Input Indicators

  • Universal AC Power 85 to 265VAC


  • Diagnostic LEDs

  • Dynamic Deadband

  • Relay Protection

  • Specifications

  • Ordering Information

q126 1

Unless otherwise specified, the factory presets the Model Q126 as follows:


Input: J Type
Range: 0 to 350°C
Output: Dual, SPDT
Trip: A: HI, B: LO
Failsafe: No
Deadband: A, B: 0.25%
q126 2
q126 table

For other I/O ranges, refer to Table 1 and reconfigure switches SW1 and SW2 for the desired input type, range and function.


  1. With the module removed from the rail and not powered, snap off the faceplate by lifting the right edge away from the heat sink. Note the input switches (SW1 & SW2) are located under the face plate. Set positions 1 through 3 on "SW1" and positions 1 through 8 on "SW2" for the desired input and range. (see Table 1)
  2. Set positions 4 and 5 of the function switch “SW1” to ON (closed) for a HI trip setpoint or OFF (open) for a LO trip setpoint (Figure 4).
  3. Set position 6 of function switch “SW1” to ON for non-failsafe operation or OFF for failsafe operation (e.g. alarm trips upon power failure).
  4. Set positions 7 and 8 of function switch "SW1" to upscale or downscale burnout.
  1. After configuring the DIP switches, connect the input to a calibrated t/c source and apply power. Refer to the terminal wiring in the Specifications section
  2. Starting Calibration: After applying power to the unit all three LEDs will flash for approximately 10 seconds. Next, input the signal level for Relay “A” setpoint, the green LED should be on. Press the CAL button and hold for 4 seconds (until the red LED starts flashing) to enter the calibration mode. The green LED should be on and the red Relay “A” LED should now be flashing.
  3. Setpoint “A”: Input the desired trip level for Relay “A”, if not already done, and push the CAL button. The green and the red Relay “A” LED should be flashing. Note, the green LED will stop flashing when the input drops below a high setpoint or rises above a low setpoint.
  4. Deadband “A”: For minimum deadband (0.25% approx.), press and hold the CAL button for 4 seconds. For high setpoints lower the input level (green LED turns off) to the desired deadband point and push the CAL button. For low setpoints increase the input level to the desired deadband level and push the CAL button. The green LED should be on and the red Relay “B” LED should be flashing.
  5. Setpoint “B”: Input the desired trip level for Relay “B”, and push the CAL button. The green and the red Relay “B” LED should be flashing.
  6. Deadband “B”: For minimum deadband (0.25% approx.), press and hold the CAL button for 4 seconds. For high setpoints lower the input level (green LED turns off) to the desired deadband point and push the CAL button. For low setpoints increase the input level to the desired deadband level and push the CAL button. The green LED should be on and both the red LEDs should be flashing.
  7. Press the CAL button one final time to exit the calibration mode. Check the setpoint and deadband to validate calibration.
Relay Protection and EMI Suppression

When switching inductive loads, maximum relay life and transient EMI suppression is achieved using external protection (see Figures 2 and 3). Place all protection devices directly across the load and minimize all lead lengths. For AC inductive loads, place a properly-rated MOV across the load in parallel with a series RC snubber. Use a 0.01 to 0.1mF pulse film capacitor (foil polypropylene recommended) of sufficient voltage, and a 47W, 1/2W carbon resistor. For DC inductive loads, place a diode across the load (PRV > DC supply, 1N4006 recommended) with (+) to cathode and (-) to anode (the RC snubber is an optional enhancement).

q126 4
q126 5


  • Range: See Table 1

  • Impedance: >1 Megohm


Input Bias

  • Current (burnout detection): <1.5 microamp

  • Overvoltage: ±10V differential

  • Common Mode (Input to Ground):   1800VDC, max.


LED Indicators 

  • Input Range (Green)    

  • >110% input: 8Hz flash

  • <-10% input: 4Hz flash


Setpoint (Red): 

  • Tripped: Solid red

  • Safe:off


Limit Differentials (Deadbands)   

0.25% to 100% of span


Response Time 

  • Dynamic Deadband: Relay status will change when proper setpoint/process condition exists for 100msec

  • Normal Mode (analog filtering): <250msec, (10-90%)



  • Effectivity: Setpoint(s) are adjustable over 100% of the selected input span

  • Repeatability (constant temp.): 

    • 0.2% for temp > 0°C

    • 0.3% for temp < 0°C



Temperature: ±0.05% of full scale/°C, max.



DC to 60Hz: 120dB



1800VDC between contacts, input and power

ESD Susceptibility   

Capable of meeting IEC 801-2 level 3 (8kV)


Humidity (Non-Condensing)     

  • Operating: 15 to 95% (@45°C)

  • Soak: 90% for 24 hours (@65°C)


Temperature Range     

  • Operating: 0 to 55°C (32 to 131°F)

  • Storage: -15 to 70°C (5 to 158°F)



2.5W max. 100 to 240VAC +10%, 50 to 400Hz


Relay Contacts     

2 SPDT (2 Form C) Relays, 1 Relay per setpoint


Current Rating (resistive)  

  • 120VAC: 5A

  • 240VAC: 2A

  • 28VDC: 5A

  • Material: Gold flash over Silver alloy

  • Electrical Life: 10^5 operations at rated load

    • Note: External relay contact protection is required for use with inductive loads (see relay protection Figures 2 & 3).

  • Mechanical Life: 10^7 operations


Wire Termination   

Screw terminations for 12-22 AWG





Agency Approvals   

  • CSA certified per standard C22.2 (File No LR 42272).

  • UL recognized per standard UL 508 (File No E99775).

  • CE EN61326, EN61010-1

Ordering Information
1. Specify: Model:   Q126-0000
2. Specify I/QRail type and quantity.
3. Accessories: (see Accessories)
4. Optional Custom Factory Calibration: Specify C620 with desired input, setpoint(s) and deadbands.
All ActionI/Q “Q” series modules will mount on standard TS32 (model MD02) or TS35 (model MD03) DIN rail. In addition, the following accessories are available:
  MD02   TS32 DIN Rail
  MD03   TS35 x 7.5 DIN Rail
  IQRL-2002   2 Position I/QRail & DIN rail
  IQRL-2004   4 Position I/QRail & DIN rail
  IQRL-2008   8 Position I/QRail & DIN rail



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