3-point or 1-point calibration

Dear,

I need to know if it is better to ask for 3-point calibration for the radar type level transmitter or 1-point calibration is enough.

radar type level transmitter is used in diesel bulk storage tank and a accuracy of 0.1% is required.

contractor is submitting 1-point calibration with +/-2mm accuracy, in some cases, I have a tank as high as 12 meters.

kindly advice and clarify what is really needed.

thank you!

Charbel

It seems that a 0.1% accuracy in 12 meters would be:
12 +/- 0.1% x 12 = 12 +/- 0.001 x 12 = 12 +/- 0.012 meters = 12 +/- 12 milimeters

So a 1-point calibration with +/- 2 mm accuracy would be even better than your required 0.1% accuracy.

Notice that at a level of 2 meters, the 0.1% accuracy requirement will be equal to the +/- 2mm error. At all levels above 2 meters, the +/- 2mm will be more accurate than your requirement. Below 2 meters, it will be slightly less accurate.