radar transmitter

How to calibrate radar level transmitter generally

It depends on what the manual says. What does it say?

I said generally

Generally you adjust:

Zero=Zero=4mA
Span=10000 lts=20mA

Run the level down to its zero point, set the transmitter to zero. Then run the level to its upper point and set the transmitter to its upper range.

Normally without knowing your model, there should be a button or software that determine what is your lowest value, then the same for the highest value. After this your unit is calibrated.
There are som sofisticated radars that include a special software to congigure it together with container geometry but that is another story.

All the radar level units I'm aware of (industrial, not tank inventory) use a configuration routine that asks for
- what the low level (4mA point) distance is from a reference point (like the bottom of the mounting flange)
- what the upper level distance (high level = 20.0mA) is from that same reference point.

There is further configuration for conversion to volume units.

A calibration that checks against a traceable standard involves shooting the radar to a reflective object at a known (traceable) distance and noting the difference between the known traceable distance and the indicated distance.

Tank inventory radar (like the former Saab, now Rosemount) probably have their own 'calibration' routines, because they're used to track high value inventory. You're on your own to research those beasts.

DP transmitters can have some means of 'wet calibrating' by sensing the applied head pressure and making that head pressure equal to 4-20mA zero or span, but radar measures distance and expects a distance value for a 4-20mA zero or span, but I haven't run into that with radar transmitter yet.