D - User's choice, commonly Density
Reference for the ISA 5.1 first letter D. Density measurement is the dominant first-letter use. Coriolis meters often surface density as a secondary variable that gets its own D-prefix tag for trending. Be careful not to confuse D as a first letter with D as a modifier. PDT, differential pressure and TDT, differential temperature put the D in the second slot, where it means differential rather than density.
Read one of your own drawings.
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Also stands for.
- Differential, when prefixing another letter, e.g. DPT for differential pressure
Common second letters.
Transmitter, DT. Density transmitter
Indicator, DI
Sensor, DE
Example tags.
Density transmitter on loop 401, often Coriolis or radiometric
Density indicator
Typical placement.
On streams where density is a process variable. Oil, water separators, slurry streams in mining, polymer reactor outlets, cryogenic services in LNG.