Calibrating temperature sensors?

It’s been a long time since I studied thermodynamics, and I don’t think I paid a lot of attention in class :grinning:

I would like to calibrate all of my Visonic sensors’ temperature readings against something that is “reasonably” accurate (+/- 1 degree maybe?). The Visonic sensors will allow me to apply an offset (once I determine what the offset should be for each one).

If I were to purchase a “laser” temperature sensor (ballpark $20 at some place like Harbor Freight), could I aim it at a sensor (or some inanimate object near it) and expect it to register the air temperature around the sensor that it is pointed at?

Or am I better off buying a known accurate thermometer and having it sit next to each sensor long enough for its reading to stabilize, and then use that reading as the basis for the offset?

PS I’m aware that the “laser” itself isn’t used for measuring temperature, but is just used to allow the human operating it to aim it in the right direction.


As someone that works in HVAC I borrowed a certified calibrated temperature sensor, put it and all my temperature sensors (SmartThings Temp/Humidity and multi-sensors) on a piece of cardboard on my counter, covered them all with a big glass bowl, and let them sit for 30 minutes. After that I read the temp on the sensor and went through setting the offsets on all of them so they read the same.

With that said they still arn’t totally accurate but they are “better”.


I wonder what the official specification is for the accuracy of the Temperature monitoring “chip” in the Sensor(s) … or if it is embedded in a chip that performs other functions just as a bonus.

Micro-sensors are incredibly tiny and sophisticated these days: Acceleration sensors literally contain microscopic pitchforks which bend according to gravity and g-forces. Gyro sensors (used in UAV Drones) literally contain spinning disks to determine the change in axis.

And yet… with all that sophistication, how come we can’t get a Temperature sensor that is factory calibrated and does not drift by the time it reaches the customer? What causes the drift? Lack of initial calibration, change in battery voltage and poor voltage regulation, air flow due to the sensor casing? Or just a really cheap “bonus” sensor that was never meant to offer any sort of consistency or accuracy? :confused:

Yeah, even after I calibrate them the best I can they still aren’t the most accurate things in the world. I will say that the dedicated temperature/humidity sensors, which it seems smart things no longer sells, we’re pretty accurate compared to the temperature sensing that is built into a multi sensor. But then again that device was designed just for temperature and humidity. I even have one inside my refrigerator which usually reports a few degrees off from what the refrigerator itself says, perfectly fine for alerting me if it ever gets above a certain threshold.

With that said this is exactly why I have a commercial grade outside air and humidity sensor tied in through ST_Anything to smart things as i was looking for accuracy to make heating and cooling decisions. ST_Anything is a good bridge between sensors that are commercially available and are made for accuracy and home automations which, in general, is more of a “close enough” approach.

Thanks for the feedback so far, but unfortunately the sensors are already mounted and I don’t have an industrial-grade thermometer handy.

I’m not seeing a “nay” or “yay” on whether a “laser” temperature sensor (which I guess measures IR) could be aimed at something near each of my sensors and be expected to yield air temperature. I’ll research further.

No, your idea of using the laser thermostat will get them at least close. I’ve seen them as far as 5゚ off so you should be able to get within a degree.

I have a Honeywell 9500 series thermostat which I checked temperature with a laser temp meter, and used a temp probe on my multi-meter. All match. I then brought the movable sensors next to the thermostat and then using the offsets I calibrated them. I returned them to their location waited for them to stabilize. Then brought the laser temp meter to the sensor location and rechecked. All matched. What I did with the non movable sensors was to use the laser to check the local temp next to the sensor and adjusted from that. For humidity I used a remote calibrated hydrometer from a weather pro to check those.

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Cool, thanks very much.