0. Quick Guide
This is a quick guide to the Helium Level Meter developed at Helmholtz-Zentrum Berlin. For more detailed information please have a look at the manual - starting with chapter 1 - Introduction.
The product is used for measuring and displaying the filling levels of liquid helium vessels. It is designed for the use of superconducting helium probes. Because the measuring parameters for the probe can be changed, the helium level meter can adapt to different probes and vessels.
The helium level meter can be integrated into the Helium Management System (HMS) from Helmholtz-Zentrum Berlin.
The delivery includes the helium level meter device(s) (serial no. DH2358) (a), the LEMO connectors on the side of the level meter for the cable which connects the level meter with the liquid helium probe of the vessel (3-pin) ((b), but not the cable, only the level meter sided LEMO connector) and the one which connects to the pressure sensor (4-pin) ((d), but again not the cable, only the level meter sided LEMO connector) and a pressure sensor (c). Every five level meters are delivered with one proprietary power supply (6-pin LEMO connector) (e). In addition, a cable for the simulation of a liquid helium probe with various resistors (10, 50, 100, 150, 200 Ohm) (f) is included.
Further accessories can be purchased optionally: a level meter holder for the helium vessels (g), a cable for the automated filling mode (5-pin) (h) and a rescue power supply for the case the level meter battery is deep discharged (i).
To protect the people dealing with the helium level meter and the device itself, some precautions should be considered. Special care must be taken due to the battery. The battery of the device contains lithium, a highly reactive metal which exposed to air or water can lead to burning and explosion. This must be prevented under any circumstances.
- Handle the product carefully.
- Do not drop the device,
- do not expose the device to water in a way different from specification (see Technical Data below),
- only use the device in the specified temperature range,
- do not drill into the device, especially the battery,
- do not burn or heat the device over the specified maximum temperature,
- do not modify the battery, especially do not remove the protective circuit or the thermal fuses of the battery,
- do not remove or damage the foil which surrounds and protects the battery,
- do not damage the battery in any way.
- Only connect the power supply to a normal mains socket which offers a voltage that is stated on the power adapter,
- do not connect or disconnect the power supply with wet hands and
- do not unplug the power supply from the mains socket by pulling on the cable but use the grips on the plug.
The helium level meter is delivered with a proprietary power supply which should be used always for charging the device.
The assignment of the connectors is:
| Connector | Assignment |
|---|---|
| 3-pin connector | Helium probe |
| 4-pin connector | Pressure sensor |
| 5-pin connector | Autofill connector |
| 6-pin connector | Battery charge |
This is a short explanation of the level meter setup assuming the usage of the Helium Management System (HMS) from Helmholtz Zentrum Berlin. The setup without using the HMS or using the device in Offline Mode is described in the manual.
- Register the helium level meter in the Helium Management System (HMS) from Helmholtz Zentrum Berlin by creating a new level meter entry via
Settings -> Levelmeter -> -Create new Levelmeter-. There, type in the name, serial number and xBee-adress (to find on stickers on the case of the device) of the new device and choose “Levelmeter default” in the field of “Level Meter Type”. - The internal resistances of the liquid helium level meter should be calibrated to achieve higher precision. After having charged the device, start the level meter by pressing the “MEASURE”-button. After a system test, the identification code of a dummy vessel needs to be typed in. If not available, press the two hidden buttons above the display simultaneously to start the Offline mode. Set the maximum and minimum resistance values in the level meter corresponding to the vessels’ superconducting helium probes which are going to be used (options page 3, default password is 001). Depending on these values the level meter demands certain resistors for doing calibration. The calibration is started via the Diagnosis menu (options p. 2, turn DiagMode on) and press “cal”. During the calibration, connect the demanded resistors to perform a linear calibration of the device in the specified range. If you don’t have the max. and min. resistances of the vessels’ probes, then characterize them first and calibrate the level meter after having obtained these values. The device is delivered pre-calibrated (at 10 Ω and 100 Ω), but new calibration increases the accuracy of the resistance measurements. A set of suitable resistors can be provided by the manufacturer. Alternatively, a resistance decade can be connected to the level meter for the calibration procedure. The results of the calibration will be accessible via the values R.Span and R.Zero (options page 5).
- Mount the level meter on a helium vessel and plug in the available sensors (see figure).
- Start the level meter by pressing the “MEASURE”-button. After a system test, the identification code of the connected vessel needs to be typed in. Then, the device connects to the HMS and the measurement parameters regarding the vessel and its probe are transferred to the level meter.
- Use the level meter: There are four modes of operation:
- Standby mode: Active when the vessel stands around – low measuring rate.
- Filling mode: Activate by pressing “FILL” to enable a high measuring rate and to assign the transferred helium to the cryostat to be filled.
- Autofill mode: With additional hardware the level meter can be triggered externally to enter the measurement mode with large measuring rate. The device sends a stop signal at a given level to stop the filling process automatically.
- Diagnosis mode: Can be entered via the options menu and enables device calibration and a comprehensive characterization of the helium probe. It also offers more detailed data about components like e.g. the battery.
If the device has become dirty, use a slightly wet cloth to clean it. Mild soap can be used but avoid any aggressive cleaner. Also please note that the level meter is not waterproof against submersion.
If the device is not needed anymore or has been broken, please do not dispose the level meter, but give it back to the Helmholtz-Zentrum Berlin.
| Property | Value |
|---|---|
| Water tightness | IP62 |
| Temperatures | -10°C – 40°C |
| Battery capacity | 9000 mAh (7.2 V) |
| Battery life | typ. 4 weeks (depending on measuring parameters) |
| Frequency band | ISM 2.4 GHz |
| Transmit power output | 1 mW – 3 mW |
| Range of wireless connection | up to 30 m (indoor), up to 90 m (outdoor line-of-sight) |