ThermoPro TP-21 Remote Thermometer Review

ThermoPro TP-21 Remote Thermometer Review
The ThermoPro TP-21 is a single-probe wireless remote thermometer with user-programmable temperature alarms and USDA-approved temperature settings. It also includes a timer function.
 
The thermometer comes with one probe that is 6" (15cm) long. The probe should not be submerged while cleaning or exposed to temperatures above 572ºF (300ºC).
 
The transmitter has a single display that indicates the temperature to 0.1º in either Fahrenheit or Celsuis. There is no backlight on the transmitter. The battery compartment has a sealing ring to repel moisture, but the manufacturer warns against using it in the rain.
 
The receiver displays the temperature alarm setting as well as the probe's temperature to 1º. Temperature can be displayed in either Fahrenheit or Celsius, independent of the transmitter's setting. If the timer is being used, its value displays on the top line above the probe temperature. The probe has an alarm setting for an upper temperature limit. There is no lower limit setting. The display backlight will flash blue after the temperature has gone up by 10º. When the probe is within 15º of the set temperature, the backlight flashes green. When the temperature reaches the alarm setting, the backlight flashes red, and the audible alarm beeps.
 
Target temperatures can be selected from pre-programmed meat and doneness values or set to the user's preference.
 
The timer operates in either an up-counter or down-counter mode. If the user sets a time value, the counter will count down to zero, displaying a flashing 00:00. If the timer is cleared to zero and started, it will count up to 23 hours and 59 minutes, but no alarm will sound.
 
If the receiver loses signal from the transmitter for over one minute, the receiver will alert the user by displaying dashes in lieu of the temperature reading, but there is no audible alarm. After 30 minutes of lost signal, the receiver will beep and turn itself off unless the timer is running. Unfortunately, there is no audible indication that the signal has been lost until 30 minutes have elapsed, a serious shortcoming that could result in a ruined meal.
 
The build quality of the electronics and the probes is above average. This thermometer is easy to use and provides the basic information that most cooks will want. The lack of a lower temperature alarm limit might restrict its utility for some users, though. The unit is covered by a one-year limited warranty that is extended to three years if you register the product online. Contact information, including an e-mail address, website and telephone number, are provided in the owner's manual and on an enclosed card.
 
We'll give this unit a Silver Medal for its build quality, performance, ease-of-use, and aesthetics.
Thermometer Function: 
Leave in Food
Leave in Cooker
Wireless Remote
Manufacturer's Suggested Retail Price: 
$39.99
Included: 
Transmitter, receiver, one probe with a cable reel, batteries, instructions, warranty card
Probes: 
length: 6" (15cm), diameter: 0.158" (4mm), tip: 0.102" (2.5mm), cable: 40" (1m)
Battery type: 
(4) AAA (included)
Battery life: 
Not specified
Min / Max: 
15.8 to 572ºF (-9 to 300ºC)
Ambient operating temperatures: 
Not Specified
Display precision: 
0.1º/1º
At 32ºF it actually reads: 
34.0
At 130°F it actually reads: 
131.5
At 225°F it actually reads: 
228.0
At 325°F it actually reads: 
331.2
Speed from 32°F to 212°F: 
n/a
Size of numbers in display: 
Temp: 0.4" (10mm)
Water resistance rating: 
Not rain-proof
Alarms: 
Audible/Visible
Weight: 
Transmitter, receiver and probes: 7.25 oz. (205g)
C/F Switch: 
Yes
Backlight: 
Yes
Adjustable: 
No
Auto shutoff: 
Yes
Colors: 
White

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About the features, specs, and technical terms

Adjustable. The accuracy of some thermometers can drift, and these thermometers can be adjusted to bring them back to the correct reading.

Alarms. Some devices can be set to alert the cook when a high or low temp is reached either with an audible alarm such as a beep or a visible alarm such as a flashing display.

App. Bluetooth and Wi-Fi enabled devices have a smartphone or tablet app that talk to the device.

Auto shutoff. If you don't use the device for a set period of time, it will shut itself off to save batteries.

Backlight. Digital thermometers are hard to read at night unless they have a backlight.

Bi-metal dial thermometers. Most bi-metal coil dial thermometers mounted in grill hoods should be called heat indicators, not thermometers. We do not recommend them. They have round clock-like readouts and the sensor uses two strips of metal bonded together and rolled into a coil. Each metal expands at a different rate, turns a shaft, and this provides the reading on a dial. Bi-metal meat thermometers can take up to 30 seconds to give a final reading and because the sensor can be 1/2" long or more they cannot read a specific location in meat. Most thermometers built into grills and smokers are bi-metal, but they are often low quality in order to keep the grill price down. They can easily become unreadable if they fill with smoke and or water. Also, these grill thermometers are mounted in the dome, where the temp can be very different from the temp at the cooking surface, which generally makes these bi-metal dial thermometers both unreliable and misleading.

C/F Switch. Most thermometers have a switch to change the display from Celsius to Fahrenheit.

K-Probes. Some thermocouple thermometers have a standardized spade-like connector for scores of interchangeable probes.

IR (infrared) sensors. Infrared-sensing thermometers measure the energy radiated from a warm surface and convert it to a temperature reading. Some surfaces emit more infrared at a given temperature than others, so some units allow the user to adjust the emissivity setting to fine-tune the accuracy of the thermometer. This should rarely be necessary unless very high accuracy is needed. These units are useful for determining the temperature of a cooking surface like a skillet or griddle.

Liquid filled thermometers. Old-fashioned liquid filled thermometers are very small glass tubes filled with a liquid that sits in a bulb at the bottom. As it warms, the liquid expands. These thermometers are slow but they can be very accurate. Because they do not need batteries, they make good refrigerator and freezer thermometers, but they cannot read a small area such as the center of a hunk of meat well.

Logging. Some thermometers can remember the readings taken over time and create a log that can either be printed or exported to a spreadsheet.

Margin of Error. Most thermometers are considered to be accurate if they are within plus or minus 3°F of the target temperature. High end thermometers are more precise than this.

Min/Max. The minimum and maximum temperatures it is capable of reading. On some devices, especially those which use different probes, the Min/Max can vary with the probe.

Oven. We often use the term "oven" to cover a range of cooking devices, including grills and smokers, which are essentially outdoor ovens.

Popup thermometers. Popups have a compound in the tip that melts at a determined temp and releases a spring that pops the stem up. This type of thermometer often comes pre-inserted in your Thanksgiving turkey. Although there is a chance that it will be accurate, the thermometer will read only one small part of the turkey, may stick, and will likely be set to a high temperature that is meant to prevent litigation rather than produce a juicy bird. The popup thermometer is often to blame when your turkey tastes like cardboard. Throw it out.

Price. Usually the manufacturer's suggested retail price. When that is not available, we use the approximate street price.

Sensor. Thermocouple, thermistor, liquid, and bi-metal. They are each described in detail above and below.

Speed. We measure how long it takes the thermometer to go from 32°F to 211°F and from 212°F to 33°F. But you have to be careful about the time manufacturers quote. Often they use an industry standard called "time constant." That is the time it takes to get to 63% of a full reading, and a full reading takes five times that. So if they say the time constant is 0.6 seconds, as does the manufacturer of the Thermapen, the unit will be precise with a full reading in about 3 seconds. Another factor to consider is how fast the display refreshes itself. The Thermapen refreshes every 0.5 seconds. This means you can slowly insert it and remove it and it will give you a new reading every 0.5 seconds. The Thermoworks K-type Fast Response Meat Probe #113-151, which can be plugged into different meters, is slightly faster with a time constant of 0.5 seconds and precise read in 2.5 seconds. But if you plug it into the MTC meter, which refreshes every 1 second, the probe is actually faster than the meter, and combined they are slower than the Thermapen. Another factor is the conductivity of the medium you are measuring. Food, which consists mostly of water, reads faster than bread, which consists mostly of air. That is because water is a better conductor than air.

Thermistors. Thermistors are usually not as quick as thermocouples. They tend to be thicker, and they can be slightly less accurate, usually with a margin of error of 5°F. These sensors are best for leaving in large roasts and ovens for continuous readings. Thermistor units send a current through a wire in the probe with a resistor in the tip. Its resistance to the electrical flow changes with temperature and the meter measures the voltage across the resistor.

Thermocouples. Thermocouples are the best food thermometers because they're fast and precise with a small sensor, making them ideal for rapid read thermometers. Their margin of error can be less than 1°F. Thermocouple probes have two tiny wires of different metals welded at the tip, most often nickel and chromium (called Type K). The heat causes a tiny voltage to appear across the dissimilar metals, which are connected to a meter that measures the voltage and calculates the temperature.

Water resistance rating. Some manufacturers simply specify that a thermometer is "water resistant," but this is not a regulated description and should be taken with a grain of salt. Some manufacturers use a third party service, the International Electrotechnical Commission (IEC). It rates devices using an International Protection rating code (an IP code). An IP code might look like this: IP65. The first digit quantifies protection against solids like dust, and the second digit quantifies protection against liquids. The digits range from IP00 to IP68. If a thermometer is rated IP65, it was tested and found to be completely protected against dust as well as protected against low pressure jets of liquid from all sides. So it is OK in the rain, but NOT protected against a swim in the BBQ sauce.

Where to buy. We provide links to some suppliers, especially to those who pay us a finder's fee if you buy from them. In some cases, our links provide a Compact AmazingRibs.com Meat Temperature Guide along with the product. You will only get the guide by following the link provided.


Best Value Awards

Gold Medal. Among the best of its type in its price category. A strong buy recommendation if this is your budget.

Silver Medal. A fine product among the best in its price category with only minor shortcomings. Recommended for purchase if a Gold Medal is not available.

Bronze Medal. A good product, better than average, but may be lacking in features or quality compared to higher rated products. Worth considering for purchase if you cannot find or afford a Gold or Silver Medal.

Not Recommended. These are products that we think are poor choices compared to competitors based on price, features, and construction quality.

Not Judged Yet. These are products that may be award caliber, perhaps even Gold Medal caliber, but we do not know enough about them yet to give them an award.


How We Test, Review, and Rate Thermometers

We purchase almost all of the thermometers we review. These are truly unbiased reviews. We do not make or sell anything, and our advertising is sold by third party ad networks. We are not involved in the process. Rest assured that when we recommend a product, it is really because we like it, not because someone has paid us to say so or because the company is an advertiser or sponsor. Manufacturers are never charged to have products reviewed or be included in the listings.

Bill McGrath, an electrical engineer, does all our thermometer testing, ratings, and reviews. He uses special equipment calibrated and rated by the National Institute of Standards & Technology to check the accuracy and speed of thermometers. He uses an ice water bath and a boiling water bath to measure the time it takes each thermometer to go from 32° to 211°F and to go from 212° to 33°F. After taking objective measurements, he evaluates based on subjective criteria such as ergonomics, ease of use, flexibility, warranty, access to support, and build quality. Finally, we consider value when giving our awards.

nist calibration machine


"The instant-read thermometer, used frequently, solves most issues." --Mark Bittman, New York Times food columnist and cookbook author

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