Environmental Factors Affecting Sensors

There are a few environmental factors which can affect sensor operation. These factors can affect the sensor’s power operations, sensing operations, and radio communication. This article will provide useful information regarding these factors.

Heat and Cold

Temperature is one of the most common factors affecting sensor operation. It will affect the different form factors differently. The supported temperature range for each form factor is listed below. It is worth noting that the supported temperature range for the sensor hardware and the batteries may be different. If operating your sensor outside of the recommended operating temperature for the battery, you may experience erratic battery performance or faster than expected battery depletion.

Coincell - Operating temperature range (board circuitry and coin cell) -7°C to +60°C (20°F to +140°F) *
Optimal battery temperature range (coin cell): +10°C to +50°C (+50°F to +122°F)
Things to note:

  1. When operating at temperatures below 50°F and above 122°F, you will likely see the battery level fall and/or rapidly deplete. If the battery level is charted with the ambient temperature, you will likely see a direct correlation between the battery level and the ambient temperature.
  2. Because the battery performance is hindered at temperatures below 50°F, coincell sensors should not be placed in fridges or freezers.
  3. It is normal for the battery level of a Coincell sensor to fluctuate, especially during frequent radio transmission (which, in one scenario, occurs when the sensor is first powered up).
    *The ALTA Temperature sensor is not meant for wet, damp, high humidity environments.

AA Commercial - Operating temperature range (board circuitry and batteries) -18°C to 55°C (0°F to 130°F) using alkaline || -40°C to 85°C (-40°F to 185°F) using lithium *
Optimal battery temperature range (AA): +10°C to +50°C (+50°F to +122°F)
Things to note:

  1. AA batteries are more robust and can be more consistent than coincell batteries.
  2. Operating AA sensors in temperatures above 122°F repeatedly for long periods (such as in bed bug temperature monitoring) can result in unexpected operation which can start to present itself at high temperatures, but start to resolve at lower temperatures. If you experience errors from AA sensors that operate at high temperatures frequently, be sure to test the sensor at room temperature after the sensor and battery temperature has become uniform to see if the issue persists.
    *The ALTA Temperature sensor is not meant for wet, damp, high humidity environments.

Industrial - Operating temperature range (board circuitry and battery) -40°C to +85°C (-40°F to +185°F)
Included battery Max temperature range -40° to +85°C (-40° to +185°F)
Things to note:

  1. The included industrial batteries should consistently withstand operation at temperatures up to the specification.
  2. Since this sensor has no venting, ambient temperature below the maximum specification often lead to temperatures above the specification inside the enclosure when combined with heat dissipation from electrical components within the enclosure. This is expected to occur around 165°F, though has not been tested. Therefore prolonged exposure to high temperatures may lead to temperatures inside the enclosure above ambient temperatures to occur within the enclosure.
  3. Temperatures below -4°F (-20°C) may result in significant battery fluctuation.

Using sensors inside freezers or refrigeration units

If your application requires you to place a sensor inside a freezer or refrigeration unit, it is recommended you use a sensor with an industrial enclosure. There are two reasons for this.

  • Because freezers are cold dry environments, outside of the freezer is generally room temperature/humidity. When the warm, humid, room temperature air comes in contact with the cold, dry, freezer air, it forms condensation which accumulates onto the sensor. This often exposes the sensor to liquid ingress and damages the components.
  • AA and coincell batteries often do not perform to specification at cold/freezing temperatures, whereas the industrial batteries in our Industrial sensors are designed for operation in such temperatures.

Firmware

A note on firmware: firmware prior to 14.x reads battery level differently than later firmware. Therefore it is normal to see battery level fluctuation more frequent on firmware prior to 14.x. Industrial sensors with firmware prior to 14.x operating inside freezers with a temperature below -4°F (-20°C), may show significant battery level fluctuation.

Radio interference

Monnit sensors operate in the sub-gigahertz unlicensed radio band. Radio interference is not common, though it can occur with devices that operate within this band. Also Electromagnetic Interference can cause fields which interrupt wireless sensor communication. Though not common, a sensor operating near equipment emitting EMI can cause radio interference and signal issues. Therefore it is important to consider this when troubleshooting signal issues. Though not always possible, an important step is to test the sensor 10-15 feet line of site from the gateway, away from any operating equipment or other possible sources of EMI. The following can often generate EMI that interferes with sensor/gateway radio communication.

  • Freezer defrosters - many defrosters run on timed cycles, so if you find your sensor frequently disconnecting, you may want to review the signal history and look for patterns/cycles.
  • Unshielded electrical wires
  • Electric DC motors
  • Other motors or centrifugal motion that generates an electrical field
  • Some forms of lighting or signs
  • Portable phones
  • Microwaves

Liquid or humidity

Coincell and AA form factors are subject to exposure to liquid ingress. Therefore operating these sensor types in wet or humid environments will result in damage to the sensor. Therefore environments that have liquid or fluctuating humidity/temperature can damage coincell or AA sensors. Therefore the NEMA rated Industrial enclosures should be used in applications where the sensor body is placed in wet or humid environments.
Note: Industrial sensors are not rated for being submerged into water.

Distance from sensor-to-sensor and the wireless gateway

Our Alta sensors can generally transmit over 1,000 feet through sheetrock walls. Although distances greater than this or other obstructions such as metal or concrete will impede the wireless signal. To ensure adequate distance from the gateway is achieved, be sure the sensor is within 1,000 feet of the gateway and not transmitting through metal or concrete.

Data rate transmission

While Monnit wireless sensor networks can support a significant number of sensors, transmissions that occur too frequently can limit the radio bandwidth of the gateway and prevent some sensor transmissions from being processed by the gateway. To allow for maximum bandwidth on your gateway, be sure the gateway does not receive more than one wireless transmission every 10 seconds.

Corrosive gases or atmospheres

Coincell and AA form factors are not designed to operate in environments with corrosive gas or vapor.

Industrial Grade Sensors | Type 1, 2, 4, 4X, 12 and 13 NEMA Rated Enclosure

Monnit’s Industrial sensors are enclosed in reliable, weatherproof NEMA-rated enclosures. Our NEMA-rated enclosures are constructed for both indoor or outdoor use and protect the sensor circuitry against the ingress of solid foreign objects like dust as well as the damaging effects of water (rain, sleet, snow, splashing water, and hose-directed water).
• Safe from falling dirt
• Protects against wind-blown dust
• Protects against rain, sleet, snow, splashing water, and hose-directed water
• Increased level of corrosion resistance
• Will remain undamaged by ice formation on the enclosure

Conclusion

Being mindful the the environmental conditions in which your sensor is operating is key to a successful deployment. If you have questions about environmental factors affecting your sensors, feel free to contact support@monnit.com .