Understanding Sensor Heartbeats, Aware States, Assessments, and Rearm

Monnit sensor operation is based on a concept called the Aware State. This term refers to an operating state of the sensor that allows for a condition detected by the sensor to be reported immediately when it is detected. There are a few components and configurations which allow for this operation to occur. This article will outline this operation.

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Event Sensors vs. Interval Sensors

To start, there are two types of sensor radio behaviors associated with Monnit wireless sensors. First, there are “Event” type sensors that respond immediately to an event as it occurs (think of event type sensors as yes/no data). Second, there are “Reading” type sensors that work on a timed basis to wake up at set intervals, gather data, transmit the data, then go back to sleep until the next interval.

Examples of event type sensors;

  • water detection
  • door/window
  • motion
  • dry contact, etc.

Examples of reading type sensors;

  • temperature
  • humidity
  • voltage
  • pressure, etc.

Heartbeats

Note: Minimum heartbeats using the free Basic iMonnit Online subscriptions are 120 minutes. In order to achieve a more frequent minimum heartbeat of 10 minutes using iMonnit Online, a paid iMonnit Premiere subscription is required. iMonnit Premiere also includes Advanced Sensor Settings, such as Aware State Heartbeats and Assessments which are not available to iMonnit Basic accounts.

Monnit sensors are battery operated and have been accordingly designed to operate with efficient use of battery power. Since the radio hardware of the sensor consumes significant power, part of this design includes the strategic radio transmission of sensor readings. Rather than streaming data through the sensor’s radio which would rapidly deplete the sensor batteries, Monnit sensors transmit readings to their gateway in intervals called Heartbeats. The default Heartbeat for sensors when they are assembled is 120 minutes, but this is configurable.

Every sensor has a heartbeat regardless of the type of radio behavior. Event type sensors use the heartbeat function to tell the system that they are still active (and will report the current sensor state as well as signal strength and battery status). Reading type sensors use the heartbeat as their set interval for gathering and sending information.

Aware State

Note: In order to immediately transmit an Aware reading, the gateway must have the Force Transmit on Aware setting enabled. This is what allows the gateway to transmit Aware readings immediately to the iMonnit portal. This setting is enabled by default.

The Aware State of Monnit sensors allows for a sensor reading to be transmitted to Monnit software immediately when a preconfigured condition is detected. Since Monnit sensors are often monitoring for events that require immediate detection, an Aware State reading allows for this to occur.

Every sensor has an aware state function. The aware state allows the sensor to function at a higher level when certain conditions are met. For event type sensors, the detection of an event automatically triggers the aware state. For reading type sensors, the user sets the conditions that must be met for a sensor to enter it’s aware state (also used for “Assessments per Heartbeat”). Once in the aware state, the sensor will operate based on the “aware state” settings.

Setting the aware state heartbeat to a quicker interval allows the user to receive more frequent sensor information and/or notifications until the sensor reports a condition that is back in the normal operation range. Also, messages flagged as aware cause the gateway to communicate to the server immediately. Standard (unaware) messages are queued on the gateway until the next gateway heartbeat (default gateway settings).

Assessments per Heartbeat

Reading type sensors also support “Assessments per Heartbeat”, where the sensor will wake up, gather data and compare it against conditions set for the Aware State, and if conditions are met, send that information to the software immediately (otherwise the sensor goes back to sleep).

The more frequently your sensor takes assessments, the more responsively the sensor can detect an Aware condition, transmit an Aware reading, enter its Aware State, and start checking in with the Aware State Heartbeat frequency.

If an Assessment does not meet the triggering condition for an Aware Message, the Assessment is discarded. There is no manner by which Assessments can be converted to data points (except for the occassion in which the Assessment is triggering an Aware State Heartbeat).

Time to Rearm

Time to Re-Arm allows the user to define how long an Event type sensor should take before it is allowed to detect another event. For example; if a motion sensor detects movement, setting a re-arm time of 1 second allows the sensor to detect movement again in just 1 second. This can allow the user to capture more frequent information if desired, but also uses more battery. Setting a re-arm time of 10 minutes preserves battery life but will not capture information again until the sensor is re-armed.

Examples of How the Aware State Works

With the sensor configurations set as shown below:
• Heartbeat Interval: 120 Minutes
• Aware State Heartbeat: 30 Minutes
• Assessments per Heartbeat: 2 (every 60 minutes)
• Aware State threshold: 257°F
• Scale: Fahrenheit.

1:00 PM -> 38°F
Sensor wakes and assesses the current conditions. The temperature read is under the threshold, not Aware, sensor transmits current temperature of 38°F. Sensor begins the countdown to 60 minutes for the next assessment to be taken and 120 minutes for the next heartbeat. The sensor goes to sleep.

2:00 PM -> 60°F
Sensor wakes and assesses the current conditions. The temperature read is under the threshold, not Aware. The sensor does NOT transmit the data as this was only an assessment, not a heartbeat, it goes back to sleep. Sensor begins the countdown to 60 minutes for the next assessment to be taken and continues the 120 minutes for the next heartbeat. The sensor goes to sleep.

3:00 PM -> 200°F
Sensor wakes and assesses the current conditions. The temperature read is under the threshold, not Aware. Sensor transmits current temperature of 200°F as it is time for the next heartbeat. Sensor begins the countdown to 60 minutes for the next assessment to be taken. The sensor goes to sleep.

3:20 PM-> 258°F
As sensor is asleep, there will be no action until 60 minutes after the last heartbeat or until the next assessment 60 minutes after the last assessment.

4:00 PM-> 258°F
Sensor wakes and assesses the current conditions. The temperature read is over the threshold, and the sensor enters the Aware State. The sensor transmits the data to the gateway with an “urgent” tag which tells the gateway to send the data to the server immediately. The Heartbeat is now set to 30 minutes, and the assessments are twice within that heartbeat, or every 15 minutes. The sensor goes to sleep.

4:15 PM-> 262°F
Sensor wakes and assesses the current conditions. The temperature read is over the threshold, is in the Aware State. The sensor does NOT transmit the data as this was only an assessment, not a Heartbeat. Sensor begins the countdown to 15 minutes for the next assessment to be taken. The sensor goes to sleep.

4:30 PM-> 262°F
Sensor wakes and assesses the current conditions. The temperature read is over the threshold, and the sensor goes into the Aware State. The sensor transmits the data to the gateway with an “urgent” tag which tells the gateway to send the data to the server immediately. The sensor sets the Heartbeat countdown to 30 and the assessment countdown to 15 minutes.

4:45 PM PM-> 258°F
Sensor wakes and assesses the current conditions. The temperature read is over the threshold, is in the Aware State. The sensor does NOT transmit the data as this was only an assessment, not a Heartbeat. Sensor begins the countdown to 15 minutes for the next assessment to be taken. The sensor goes to sleep.

5:00 PM -> 258°F
Sensor wakes and assesses the current conditions. The temperature read is over the threshold, and the sensor remains the Aware State. The sensor transmits the data to the gateway with an “urgent” tag which tells the gateway to send the data to the server immediately. The sensor sets the Heartbeat countdown to 30 and the assessment countdown to 15 minutes. The sensor goes to sleep.

5:15 PM -> 256°F
Sensor wakes and assesses the current conditions. The temperature read is under the threshold. The sensor has left the Aware State. It does NOT transmit the data as this was only an assessment, not a Heartbeat. The sensor continues the countdown to the next heartbeat. The sensor goes to sleep.

5:30 PM
Sensor wakes and assesses the current conditions. The temperature read is under the threshold, and the sensor is not Aware. The sensor transmits the data to the gateway. The sensor sets the Heartbeat countdown to 120 and the assessment countdown to 60 minutes. The sensor goes to sleep.

Conclusion

Understanding the Aware State operation of a sensor is critical in terms of efficient operation of the sensor’s battery while considering the need for timely sensor readings and the number of data points required. If you have inquiries regarding these unique operational configurations, feel free to contact Monnit Support.