Programmable Dual-Output Temperature Controller

Model: TD420A

$84.99

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Product Update (4/16/2025): A new model TD420A with upgraded firmware is now available to replace the older model TD420P. A user can now program up to 8 steps with more flexibility to achieve single-step, multiple-step, and infinite loops. Please check the manual for details.

The TD420A is a plug-and-play, dual-output temperature controller equipped with updated firmware (v1.3.5), offering significantly enhanced programming capabilities compared to the previous model TD420P.

It supports up to eight programmable steps spanning up to 33 days. For each step, users can define a target temperature and a step timer, or even configure a special action. Programs can run either in a linear sequence or as a loop, depending on program configuration.

This controller can be used for applications such as beer fermentation, sourdough rising, or in research studies where the environment needs to be controlled in certain cycles. The TD420A is a plug-and-play controller. No wiring is needed for the heater or cooler.

The controller comes with one temperature probe and provides two independent outputs: one for cooling devices (e.g., refrigerators, ventilation fans); one for heating devices (e.g., space heaters, heating lamps). By using both outputs, users can maintain the desired chamber temperature regardless of external conditions.

Both heating and cooling control modes are simple on/off control, similar to a mechanical thermostat but with much higher precision due to an adjustable hysteresis band, precision sensor, and digital readout. An anti-short function is available to protect the compressor from frequently cycling on/off with high-pressure Freon.

Unlike many other temperature controllers with economic NTC/PTC thermistor sensors, a digital silicon band gap sensor is used in this controller. The advantage of this digital sensor is its reliability in moist environments than a thermistor sensor. It can be fully immersed in water over extended periods without any issues, and perform with more precision and uniform accuracy over an entire specific temperature range. In addition, the cable of the sensor comes with food-grade silicone insulation, as compared to PVC jackets used on most sensors on the market. Silicone is safer than PVC for food applications, especially when immersed in solutions that contain alcohol. This is because flexible PVC contains plasticizers that can leach out in alcohol. Silicone is also able to withstand higher temperatures.

Note: This controller is only compatible with a silicone bandgap sensor. It is not compatible with PT100 RTD sensors.

Specifications:

Temperature Control Range	-50 ~ 105°C, -58 ~ 221°F
Temperature Resolution	0.1°C (between -9.9 ~ 99°C) 1°C (between -50 ~ 10°C, 100 ~ 120°C) 0.1°F (between -9.9 ~ 99.9°F ) 1°F (between -58 ~ 10°F, 100 ~ 248°F)
Temperature Accuracy	0.5 °C or 0.9 °F
Temperature Control Mode	On/Off Control. Heating and Cooling
Temperature Control Output	10 A, 120 V or 240 V AC *
Timer Range	Each step: 0.1 to 99.9 Hrs or 1 to 999 Mins
Timer Resolution	0.1 hours or 1 Minute
Max Programmable Time	799.2 hours or 33.3 days (for a total of 8 steps)
Audio Alarm	High and low limit
Sensor Type	Silicon Band Gap Sensor
Sensor Size	0.24" OD. (6.0 mm), 2" Length (50 mm)
Ambient Temperature	-20~ 50 °C
Dimension	91 x 140 x 46mm
Input Power	85 ~ 242 VAC, 50 Hz / 60 Hz
Sensor Cable Length	6 ft (2 m)
Power Cable Length	3 ft (1 m)

Warranty: One (1) year limited warranty. See here for details.

Note:

The controller can display temperature in Celsius or Fahrenheit.
Unlike other PID controllers that we sell, this on/off controller will not hold temperature as tight if the system has a very slow and delayed response. Some temperature overshoot is normal.
Either heating or cooling device is limited to 10 Amps. The output voltage is the same as the input voltage. When the controller is plugged into 120 VAC, the output will be 120VAC. If the controller is connected to 240 VAC, the output will be 240 VAC.
The input power plug is a US NEMA 5-15P plug. The output sockets are US NEMA 5-15R. Optional input & output travel plug adapters are offered. Please check here for more details.