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ThermoPro TP-420 IR and Instant Read Thermometer Review

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ThermoPro TP-420 IR and Instant Read Review

The ThermoPro TP-420 is a combination infrared (IR) gun and an instant-read thermometer at an attractive price point. The infrared sensor gives the user the temperature of a cooking surface and the probes measure the internal food temperature.


The sensor has a 12:1 measurement cone, meaning that at 12″ from a surface the sensor will detect the temperature in a 1″ diameter circle. This allows the user to point the sensor at a small area, giving better control of the measurement. There is no laser pointer, so one has to be careful to orient it toward the surface of interest. Pressing the Scan button activates the IR sensor, and it takes measurements for the duration of the button push. When the button is released, the measurement is held. Pressing the Mode button toggles through the held value, the minimum value, and the maximum value observed during the Scan. Oddly, the display is upside down when the sensor is pointed downward, and the display does not rotate as the thermometer’s orientation is changed. Using two expensive ThermoWorks IR thermometers as references, the ThermoPro unit read about 20°F higher at 400°F than the reference thermometers. This is probably an acceptable deviation.

An infrared thermometer’s reading is dependent on a parameter called emissivity. It relates to how much energy is radiated from the surface at a given temperature. A dark surface emits more energy than a shiny surface. For maximum accuracy, the value set in the thermometer should match the emissivity of the surface being measured. This thermometer allows the user to adjust the parameter if desired. It comes set at 0.95 by default, a value used by most thermometer manufacturers. Most users will never change the factory’s setting.


The probe has its own temperature display. It shows the instantaneous temperature value; there is no hold/min/max function. Again, the display does not rotate, so the reading must be taken from the measurement position. this is slightly awkward, but not a deal breaker. The probe’s accuracy at food temperatures was very good, and the response time was also good.

The build quality of this thermometer leaves something to be desired. There are many nooks and crannies where food residue could accumulate which can be a possible hygiene problem. The battery cover does not include any seals to prevent water entry, so the user must be careful around a faucet. Better thermometers, including the most recent ThermoPro offerings, are constructed with seals to impede water ingress. Perhaps this failing is OK at this price point, but it is a risk. You could spend several times the price of this thermometer to get better moisture immunity if you’re so inclined.

As my wife likes to remind me, you don’t get what you don’t pay for. This is true with this thermometer. Design and construction reflect the price point. This is the least expensive IR/instant read thermometer I’ve tested. It performs well but is vulnerable to moisture and food contamination. If you’re careful with your tools, this thermometer could be a good value. If not, this might not last long. Ultimately it is your call, your choice.


The warranty isn’t stated in the accompanying materials. Contact info for the manufacturer includes telephone numbers and an e-mail address. The user’s manual is well-written and comprehensive. Overall, this is a decent value that gets a Silver Medal for price/performance ratio.

  • Thermometer Function:
    Hand Held, Infrared Gun
  • Item Price:
    $ 29.99
  • Where to buy (buying from this supplier supports this website):
  • Probe:
    Length: 4.25" (108mm), diameter: 0.138" (3.5mm), tip: 0.081" (2mm)
  • Battery Type:
    2xAAA (supplied)
  • Battery Life:
    Not specified
  • Safe Operating Range:
    Not specified
  • Min & Max Temp:
    IR: -58 to 1022°F (-50 to 550°C); Probe: -58 to 572°F (-50 to 300°C)
  • Display Precision:
  • Actual Temp at 32 Degrees:
  • Actual Temp at 130 Degrees:
  • Actual Temp at 225 Degrees:
  • Actual Temp at 325 Degrees:
  • Speed from 32 to 212 Degrees:
  • Speed from 32 to 212 Degrees:
  • Numbers Display Size:
    IR: 0.40" (10mm); Probe: 0.36" (9mm)
  • Water Resistance Rating:
    Not water resistant
  • Weight:
    4.15 oz. (117g)
  • C/F Switch:
    Built in CF switch
  • Backlight:
    Built in Backlight
  • Auto shutoff:
    Has Auto Shutoff
  • Color Options:
  • Thermometer Sensor:
  • Additional Features:
    Min/Max/Hold button for IR sensor
  • Included:
    Thermometer, batteries, instructions
  • Alarms:

Published On: 8/4/2022 Last Modified: 8/11/2022

  • Bill McGrath - Bill McGrath is's Thermometer Maven. He has sophisticated equipment, an electrical engineering degree from Cornell University, and an MBA (almost) from UC Berkeley. Despite being mostly retired, he is still the person responsible for developing and updating all of ExxonMobil's training modules.


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