I will set out the scenario first then look at how I am use gauge queries.
I am monitoring diesel driven pumps. RPM should stay relatively constant, though RPM will increase/descrease slowly over time.
At times however set point’s on one of a series of pumps may be wrong and the pump speeds up/slows down rapidly over a large RPM range., This due to PID loops being too aggressive and/or target pressures incorrect .
The plan is to send out an alert when the MAX and MIN RPM values for a pump over 20min period vary by more than 50rpm for instance.
So plan was to use the gauge query for all devices with a particular tag and value hasRPM=true. so far so good.
Then use device id specified in the current payload to pick the device for the query and collect the MIN, and a seperate query to get the MAX.
However I find the pay load only every gets a timestamp and no value.
Here is the gauge settings
However if I select specific device/tag I do get a MIN value set in the payload.
To me it seems the device id in payload doesn’t work as I expect.
Can you shed some light