Cryogen Liquid Level Monitors

LN2 Level Meter:

The liquid nitrogen level meter probe is a Magnex Scientific E5031. The probe is a continuous analog readout of the liquid nitrogen level. The active sensor area of the probe is approximately 1 meter. Read-out of the probe is done via a "hockey-puck" like attachment that screws into the top of the ~1m long probe rod. The probe is calibrated using a combination of a Zero offset adjustment on the hockey-puck and Gain adjustment on the back of the analog read-out. Typically the meter is calibrated using a known liquid level. The ammonia sample dewar is a good place to calibrate the liquid level if you think it is off. We usually only use the meter as a rough estimate of the liquid level so the calibration doesn't have to be super precise.

File:Http://nuclear.unh.edu/~ryan/images/HockeyPuck.jpg