Temperature sensors are a great example for alerting because they fluctuate constantly, have multiple seasonalities, and failures can be subtle. In the end, you'll want:
1. If the sensor dies and there is no data at all
2. If the sensor gets stuck (giving same value)
3. If the sensor slowly drifts (adjusting for daily, weekly, and yearly seasons) - indicating a clogged filter or leaking refrigerant
4. Statistical spikes - this is the hardest to tune so you need to treat it as a model that detects anomalies and it takes a long time to label extremely rare events
5. Static thresholds, over varying windows to deal with sensor error and transient spikes.
It also raises questions like "if the sensor is reporting 400C then either the building is on fire or the sensor is broken", or "how do we get the alert if the building is indeed on fire" and the inevitable followup: do we even need to get an alert if the building is on literal fire?
> It also raises questions like "if the sensor is reporting 400C then either the building is on fire or the sensor is broken", or "how do we get the alert if the building is indeed on fire" and the inevitable followup: do we even need to get an alert if the building is on literal fire?
Haha, I was looking at a BAS front end with a customer and we were trying to figure out why an air handler kept tripping out. The return air duct static pressure sensor was reading 65536 kpa, so either the sensor was faulty or the building was moments away from being vaporized in a massive explosion. Replacing the sensor corrected the issue and hundreds of lives were saved ;)
Maybe they should be directly monitoring the AC if they are so concerned about it. Having temperature sensors are nice, but there are plenty of ways to detect what the AC unit is actually doing. These are all very common BAS control problems.
I came to comment the same thing but in reading the verbiage your context does not match my use of the term "AC".
I would offer that instead of monitoring the reactive egress of the devices purpose, thermal deltas, that one instead monitors the proactive ingress of what it needs to function to produce those thermal deltas, Alternating Current. If the devices native monitoring does not offer taps for voltage and amperage consumption then adding this before each device should be considered, certainly in data centers as some here have direct experience with HVAC failures and remaining on site for days to keep the uptime up. As a typical energy consuming device ages one can derive and relate many reactive events over time from proactive energy monitoring and in doing so one is certain to learn something new.
BAS systems usually include a current transformer or current switch around one of the ‘hot’ conductors feeding the piece of equipment to let you know if it is using electricity (or not), aka “status”.
Edit: the user you were replying to was using AC as an abbreviation for air conditioner, not alternating current.
I recently came across almost exactly this with my smoker! I have a controller which uses ambient and meat temperature probes and a fan to control the fire’s temperature. I need to know when the ambient temperature falls below a certain point as I then have to intervene before dinner is ruined. I also want to know when the fan is struggling to keep up, as that means the fire needs more fuel, and it’s easier to deal with that before the temperature drops too low.
I love that I have taken humanity’s oldest technology and complicated it to the point where I have the same problems as the buildings running our very newest technology. Makes a good brisket though.
Temperature sensors are a great example for alerting because they fluctuate constantly, have multiple seasonalities, and failures can be subtle. In the end, you'll want:
1. If the sensor dies and there is no data at all
2. If the sensor gets stuck (giving same value)
3. If the sensor slowly drifts (adjusting for daily, weekly, and yearly seasons) - indicating a clogged filter or leaking refrigerant
4. Statistical spikes - this is the hardest to tune so you need to treat it as a model that detects anomalies and it takes a long time to label extremely rare events
5. Static thresholds, over varying windows to deal with sensor error and transient spikes.
It also raises questions like "if the sensor is reporting 400C then either the building is on fire or the sensor is broken", or "how do we get the alert if the building is indeed on fire" and the inevitable followup: do we even need to get an alert if the building is on literal fire?
> It also raises questions like "if the sensor is reporting 400C then either the building is on fire or the sensor is broken", or "how do we get the alert if the building is indeed on fire" and the inevitable followup: do we even need to get an alert if the building is on literal fire?
Haha, I was looking at a BAS front end with a customer and we were trying to figure out why an air handler kept tripping out. The return air duct static pressure sensor was reading 65536 kpa, so either the sensor was faulty or the building was moments away from being vaporized in a massive explosion. Replacing the sensor corrected the issue and hundreds of lives were saved ;)
Maybe they should be directly monitoring the AC if they are so concerned about it. Having temperature sensors are nice, but there are plenty of ways to detect what the AC unit is actually doing. These are all very common BAS control problems.
I came to comment the same thing but in reading the verbiage your context does not match my use of the term "AC".
I would offer that instead of monitoring the reactive egress of the devices purpose, thermal deltas, that one instead monitors the proactive ingress of what it needs to function to produce those thermal deltas, Alternating Current. If the devices native monitoring does not offer taps for voltage and amperage consumption then adding this before each device should be considered, certainly in data centers as some here have direct experience with HVAC failures and remaining on site for days to keep the uptime up. As a typical energy consuming device ages one can derive and relate many reactive events over time from proactive energy monitoring and in doing so one is certain to learn something new.
BAS systems usually include a current transformer or current switch around one of the ‘hot’ conductors feeding the piece of equipment to let you know if it is using electricity (or not), aka “status”.
Edit: the user you were replying to was using AC as an abbreviation for air conditioner, not alternating current.
I recently came across almost exactly this with my smoker! I have a controller which uses ambient and meat temperature probes and a fan to control the fire’s temperature. I need to know when the ambient temperature falls below a certain point as I then have to intervene before dinner is ruined. I also want to know when the fan is struggling to keep up, as that means the fire needs more fuel, and it’s easier to deal with that before the temperature drops too low.
I love that I have taken humanity’s oldest technology and complicated it to the point where I have the same problems as the buildings running our very newest technology. Makes a good brisket though.
Awesome, that's exactly what a hobby should be! Sounds like you are creating some really delicious food :)