We are often asked questions such as "Where should I place my sensor?" or "How much area does it cover?" The short answer is, "it depends."
First, let's address coverage area. A SensorPush sensor, or really virtually any thermometer, hygrometer or barometric pressure sensor is really only measuring conditions at a single point. However, when considering how many sensors you may need and the best way to place them for a given area, it is important to identify your goals and the general nature of the space and its conditions. Depending on these factors, you may find that one sensor is enough for an entire warehouse, or that you need a sensor on each shelf!
It largely depends upon how consistent conditions are within your area of interest. If it is very uniform then one sensor, or perhaps a small number of sensors, will give you a good representation of the conditions. However, if there is some factor that causes conditions to vary widely, such as sources of heat or moisture or perhaps strong air currents (or very still air leading to temperature stratification due to hot air rising), you may need more sensors to get the information you're seeking.
Regarding placement, often revisiting or clarifying your goals can help point you in the right direction. For instance, if your goal is to monitor comfort in a pet's room, a single sensor closer to the area where the pet sleeps is likely fine, as you're not as concerned with the temperature variation on top of the heat register across the room. But if you're trying to get a picture of how your HVAC system operates, you might instead want the sensor placed in the register!
If you're concerned with potential moisture issues in the basement, you may want to try to ascertain what is generally the dampest area, and place the sensor there so you can address an issue when it arises. Or you may want multiple sensors in various locations to try to get a picture of the cause of the issues in the first place.
In a refrigerator, you might just want to monitor the area where the most perishable food is stored, or you might want to instead measure what is most likely to get the warmest (e.g. the upper area of the door, or the area farthest from the air vent). Or maybe what you're most interested in is the variation in different areas, in which case you might put multiple sensors in to study the differences between them, (perhaps exporting data to a CSV file for further analysis in Excel or another spreadsheet).
In the end, the uses are endless, and the flexibility of the devices rewards and encourages experimentation. Perhaps the best advice is to start with your best guess and then let your curiosity and intuition be the guide.
How to Mount/Hang Your Sensor
Once you've decided where to put it, the next step is to figure out how to mount it. Some sensors come with a small disc of double sided tape, which can be used, or you can find your own. We also find that 3M Command Strips work quite well and are easy to remove without damaging either the sensor or the mounting surface.
It is important to consider that mounting the sensor directly to a surface means that there will be a certain amount of thermal coupling between the surface and the sensor. For instance, mounting the sensor to a wall that tends to be excessively warmed by the sun will likely lead to the sensor reading temperatures that are higher than the actual ambient air temperature. In many situations where there isn't a large temperature variation between a surface and air, this isn't a significant problem. But for optimal thermal decoupling and ambient airflow, it's a good idea to hang the sensor from a short piece of string, or perhaps a small zip tie using the mounting hole of the sensor.
In either case, for optimal accuracy, you'll want to mount the sensor in a place where it's shielded from direct solar radiation or other infrared radiation (e.g. from strong artificial light sources or a fireplace). If the case gets heated by such radiation, the measurements will inevitably be skewed.
While some SensorPush sensors are designed specifically to be water-resistant and are able to be splashed or otherwise come in contact with water or rain (but not submerged), it's a good idea whenever possible to protect them from direct rainfall or other water contact, although it's of course most important with models such as the HT1. On the HT1, the back side of the case has some writing on it and also a small hole. This hole is where the humidity and temperature sensing chip takes moisture and temperature readings, so that's where the sensor is most sensitive. That hole needs airflow, but make sure it's protected from contaminants like water and dust (The big hole that's in the corner of the device, going all the way through the case from front to back is designed for hanging the sensor with a wire tie, string, screw, etc.).