EMS Expression Data Parsing Rules
Supports data references by device, time offset, and sample position.
Query data from a past time
Section titled “Query data from a past time”Rule: dataKey[-NTimeUnit]
Example: PCS_交流A相电流[-1s]
Meaning: retrieve the value of PCS_交流A相电流 from 1 second ago.
Time-offset units:
ms/millisecond/milliseconds s/sec/second/seconds m/min/minute/minutes h/hour/hours d/day/days w/week/weeks M/month/month
Query the Nth most recent value
Section titled “Query the Nth most recent value”Rule: dataKey[#nth]
Example: PCS_交流A相电流[#3]
Meaning: retrieve the third most recent value of PCS_交流A相电流.
Use slave-device data
Section titled “Use slave-device data”Rule: [DeviceCode]datakey
Example: [DeviceA]PCS_交流A相电流
Meaning: retrieve the latest shared value of PCS_交流A相电流 from slave device DeviceA.
Combine rules
Section titled “Combine rules”The rules above can be used together.
Example: [DeviceA]PCS_交流A相电流[-1s,#3]}
Meaning: retrieve the third most recent shared value of PCS_交流A相电流 from slave device DeviceA at 1 second ago.