Cryomagnetics level monitor

Cryomagnetics manufactures cryogenic liquid level monitors, which are used for monitoring liquid nitrogen or helium levels inside cryostats. The two level meters supported in the package are LM-500 and LM-510; despite difference in appearance, their functionalities are very similar, so their interfaces are nearly identical.

The main device classes are pylablib.devices.Cryomagnetics.LM500 and pylablib.devices.Cryomagnetics.LM500.

Software requirements

LM-500 provides a bare RS232 interface, so any appropriate USB-to-RS232 adapter should work. LM-510 has a USB interface with a built-in USB-to-RS232 adapter, which is automatically recognized as a serial port, so no additional software is required.

Connection

Since the devices are identified as COM ports, they use the standard connection method, and all you need to know is their COM-port address (e.g., COM5):

>> from pylablib.devices import Cryomagnetics
>> sensor = Cryomagnetics.LM510("COM5")
>> sensor.close()

Operation

The operation of this temperature sensor is fairly straightforward, but there is a couple of points to keep in mind:

Upon connection the devices are automatically switched into the remote mode, which disables manual controls. If this mode is manually switched off (e.g., using Local button in LM-510), the device will no longer obey the remote commands, even though the readout would still work.

There are no specific commands for stopping a refill or resetting the timeout state after a timed-out refill. However, both can be achieved using LM500.reset() method.

Only LM-510 supports switching the automated refill option on and off using LM510.set_control_mode() method.

Like most similar devices, querying the level using LM500.get_level() immediately returns the most recently measured value. Re-measurement is periodically initiated by the devices itself, or can be initiated manually using LM500.start_measurement() or LM500.measure_level().