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.

Description of images (starting top left and working clockwise):

• 1. Front of the Magnex Scientific LN2 Liquid Level and AMI Model 135 Liquid Helium Level Monitor. We currently do not use the Magnex E5011 Monitor.
• 2. Back of the Magnex Scientific LN2 Liquid Level and AMI Model 135 Liquid Helium Level Monitor. The gain for the LN2 monitor is adjusted using a small screw driver. The cable labeled LHe J1 for the AMI sensor originates in the 35 pin connector on top of the blue AMI magnet dewar.
• 3. The hockey puck attachment for the E5031 LN2 probe. The puck is attached to the probe rod in this picture.
• 4. The LN2 probe cable that attaches to the base of the hockey puck.
• 5. The LN2 probe cable that attaches to the back of the read-out electronics.
• 6. The zero offset adjustment on the hockey puck. This is changed with a small screw driver.