Environmental Factors Affecting Sensors

A few environmental factors can affect sensor operation. These factors can affect the sensor’s power operations, sensing operations, and radio communication. This article will provide helpful 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 you operate your sensor outside the recommended operating temperature for the battery, you may experience erratic battery performance or faster-than-expected battery depletion.

Coin Cell - 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, the battery level will likely fall and 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, coin cell sensors should not be placed in fridges or freezers.

3. It is typical for the battery level of a Coin cell 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 consistent than coin cell batteries.

2. Operating AA sensors in temperatures above 122°F repeatedly for extended 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, test the sensor at room temperature after the sensor and battery temperature have 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 leads to temperatures above the specification inside the enclosure when combined with heat dissipation from electrical components. This is expected to occur around 165°F, though it has not been tested. Therefore, prolonged exposure to high temperatures may lead to temperatures inside the enclosure above ambient temperatures occurring 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, you should use a sensor with an industrial enclosure. There are two reasons for this.

• Because freezers are in cold, dry environments, the air 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, condensation forms, which accumulates on the sensor. This often exposes the sensor to liquid ingress and damages the components.
• AA and coin cell 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 before 14.x reads battery level differently than later firmware. Therefore, it is customary to see battery level fluctuation more frequently on firmware before 14.x. Industrial sensors with firmware before 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 that interrupt wireless sensor communication. Though not common, a sensor operating near equipment emitting EMI can cause radio interference and signal issues. So, it's important to consider this when troubleshooting signal issues. Though not always possible, an important step is to test the sensor within a 10-15-foot line of the 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 generate an electrical field
• Some forms of lighting or signs
• Portable phones
• Microwaves

Liquid or Humidity

Coin cell and AA form factors are subject to exposure to liquid ingress. Therefore, operating these sensor types in wet or humid environments will damage them. Environments that have liquid or fluctuating humidity/temperature can damage coin cell 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 in water.

The standard commercial humidity specification for electronics is 30% to 50%. Our commercial products can withstand 95% non-condensing without damage.

Distance from Sensor to Sensor and the Wireless Gateway

Our ALTA Sensors can generally transmit over 2,000 feet through sheetrock walls when connected to an ALTA XL Gateway. However, distances greater than this or other obstructions such as metal or concrete will impede the wireless signal. To ensure adequate distance from the gateway, ensure the sensor is within 1,200 (ALTA) to 2,000 (ALTA XL) feet of the gateway and not transmitting through metal or concrete.

Also, sensors that are too close will struggle to maintain communication. Sensors should be a minimum of 10 feet from the gateway and not closer.

Our ALTA Site Survey Tool can help you determine each sensor's expected signal strength and quality when you set them up.

Data Rate Transmission

While Monnit ALTA 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 maximum bandwidth on your gateway, be sure the gateway does not receive more than one wireless transmission every 10 seconds.

Corrosive Gases or Atmospheres

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

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

Monnit Industrial Sensors are enclosed in reliable, weatherproof NEMA-rated enclosures. Our enclosures are constructed for indoor or outdoor use and protect the sensor circuitry against the ingress of solid foreign objects like dust and 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 of the environmental conditions in which your sensor operates is vital to a successful deployment. If you have questions about environmental factors affecting your sensors, contact support@monnit.com.