From an elog by Brian Evans:

http://midtwist.triumf.ca:8081/EL/020812.0?exp=twist

The LN2 probe and meter was calibrated to 0%.

Probe cover removed with power on and RV1 was adjusted to get -5.00 volts
between ground and pin B.

Rack mounted indicator unit was adjusted to 0%  using RV3. Output voltage at
0% is 568mV.

Unit still needs calibration when 100% full.

Notes:

Tools required at probe head: 3/16 flat screwdriver, pot twiddler, DVM with
one ground clip and one probe.

The board has been coated with plastic so the probe needs to be dug in just
under the heat shrink on wire B.

Care must be taken in removing the connector plate and sleeve under power
and reassembling the same. Also when installing the screws make sure that
there is no wire in the way.