1. Introduction

A helium level meter measures and displays the liquid helium level of liquid helium reservoirs. The model developed at the Helmholtz-Zentrum Berlin is optimized for liquid helium vessels which use a superconducting liquid helium probe and offers a wide range of advanced functions including the following ones:

1. Integrate the device into the institute-wide Helium Management System (HMS) developed at the Helmholtz-Zentrum Berlin in order to monitor the usage of helium and detect leakages. The measurement data are transferred wirelessly from the level meter to the HMS.
2. Adapt to different superconducting liquid helium probes and vessels by characterizing the probe with the level meter’s sophisticated analysis capability (diagnosis mode) and setting various parameters for reliable measurements.
3. Read out a pressure sensor to measure the pressure inside the vessel.
4. Manual measurement: Perform a single measurement of the liquid helium level when needed.
5. Standby mode: Perform regular measurements with a low frequency (~1/h) to observe the vessel parameters (especially the liquid helium level) while standing around.
6. Filling mode: Perform regular measurements with a high frequency (~2/min) to observe the vessel parameters (level and pressure) during transfer of liquid helium.
7. Autofill mode: Use the device for automated filling procedures to prevent the complete emptying of the vessel.

This manual gives a comprehensive overview about many topics relevant for the usage of the HZB level meter. The components and technical specifications of the HZB level meter are given in chapter 2 while each page and parameter of the user interface are explained in chapter 3. An overview of the operation of the device including the initial setup and the daily usage can be found in chapter 4. Chapter 5 explains the circuit of the helium probe and how to characterize it in order to find the best measurement parameters. Chapter 6 provides assistance with some problems and errors to help troubleshooting. In the appendix, there are the layout diagram of the level meter and the server communication API.