The Falcon and Eagle are often used for sensor monitoring. Sensor values are stored in device analog data fields. Generally, sampling a sensor does not use very much energy in comparison to uploading data. So in many applications, we may sample many data points, and upload in batches. For example, read the temp every 10 minutes, and update every 2 hours. This will give us detailed data for review, and ensure long battery life.
However, uploading infrequently does not help us with alerts/early warning of certain events. For example our fridge being over 10 degrees. We can use analog thresholds to force the device to upload immediately when this occurs.
This enables us to set up conditions on the device like:
- Sample the temperature every 10 minutes
- Upload every 4 hours
- If the temp ever exceeds 10 degrees, immediately upload, and keep uploading the value with every 10 minute sample until it drops back below this value.
So importantly, if we configure an analog threshold, the sample period (i.e. whatever we set up in our Task Schedule) controls how quickly we will be notified of any breaches of our thresholds,
Core components of an Analog Threshold.
There are 2 components which must be configured for an Analog Threshold to operate. These are:
- Analog Input:
- The analog input which the threshold will be evaluated against. i.e. our sensor must be correctly wired, configured, and a Configuring Task Schedules
- Enable Low/High/Delta Threshold:
- The bounds of the thresholds which would trigger an alarm.
- Analog Input:
- Select the analog input value which will be evaluated with a threshold. When the value of the chosen analog input exceeds the specified range, an alarm is raised which can be handled in a configurable manner.
- Enable Low Threshold:
- Set the lower boundary of the threshold range. If disabled, the lower boundary becomes infinitely low which will not be exceeded. If both the low and high thresholds are disabled, the threshold will never be exceeded.
- Enable High Threshold:
- Set the upper boundary of the threshold range. If disabled, the upper boundary becomes infinitely high which will not be exceeded. If both the low and high thresholds are disabled, the threshold will never be exceeded.
- Enable Delta Threshold:
- Set the upper boundary of the delta threshold range. If disabled, the boundary becomes infinitely high which will not be exceeded.
- High Threshold Value:
- Set the value of the upper threshold boundary.
- Low Value Threshold:
- Set the value of the lower threshold boundary.
- Delta Threshold Value:
- Set the value of the delta threshold boundary. The value can either be positive or negative.
- High and Low Hysteresis:
- The value below the upper / above the lower boundary which the analog input value must return to before turning off the alarm. This prevents constant alarm triggering when the analog value is hovering around a high or low threshold boundary value.
- Delta Hysteresis:
- The value below the delta boundary which the change in analog input value must return to before turning off the alarm. This prevents constant alarm triggering when the analog value is hovering around a delta threshold boundary value. The value must be positive.
- Upload On Start Event:
- Upload on triggered alarm due to the value exceeding any of the thresholds for the first time. The alarm will remain active until the value returns to the desired threshold range. A record is automatically logged when the alarm is activated.
- Log Record On Event End:
- Log a record on end of alarm due to the value returning to the threshold range for the first time.
- Upload On Event End:
- Update a record on end of alarm due to the value returning to the threshold range for the first time.
- Log Record Every Event:
- Log a record every time the value is checked, regardless of alarm state.
- Upload Every Event:
- Upload a record every time the value is checked, regardless of alarm state.
- Digital Alarm Input:
- Select a digital input which will store the current value of the alarm.
Settings of an Analog Threshold:
Create an Analog Threshold:
To create a new Analog Threshold, add one of the ‘Analog Threshold’ parameters to the system parameters. Disable (or change) the heartbeat period if it is not required.
Analog Threshold example:
Say you wanted to monitor the temperature range of a temperature sensor mapped to analog input 10, ensuring it stays within a 20 - 30 degree Celsius range with uploads whenever the alarm state changes. You would set the Analog Input to "Input 10", set Enable Low Threshold and Enable High Threshold to "Yes", set the High Threshold Value to "3000" and the Low Threshold Value to "2000". You would also set Upload On Start Event to "Yes" and Upload On Event End to "Yes". Finally, you could set High and Low Hysteresis to "500" (5%) to prevent constant alarm triggering.
Now say that you also wanted uploads whenever the temperature sensor registers a decrease in temperature of 2.5 from the previous reading.
Additionally we want to be alerted if we go outside the band of 20→30 degrees.
You would set Enable Delta Threshold to "Yes" and the Delta Threshold Value to "-250". The previously set Upload On Start Event and Upload on End Event parameters would now hold for both the high and low thresholds as well as for the delta threshold. Finally, you could set Delta Hysteresis to "50" to prevent constant alarm triggering.
These settings can be changed in the system parameters on the OEM server. The default settings are shown below: