Bruker NMR AV4 BSMS System, User Manual

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BSVT Concept
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• When the target strength (= cooling power) of the cooling unit is set, nothing happens, and
the actual strength remains unchanged - why could this happen?
BSVT operation is required for activation of a connected cooling unit. As soon as the
BSVT is
On , the actual cooling strength changes to the required value defined by the
target strength parameter. In addition, the rotary knob of the new BSCU cooling units must
be set to
Remote position. Otherwise, the settings of the TopSpin software are ignored
and the locally set strength (by rotary knob position) is considered for operation.
Note: The BCU-X requires a minimum VT gas pressure and gas flow before it becomes
active. If there is no gas flow (or no gas supply) then a connected BCU-X cannot be
detected by the VT adapter.
• Which channel is the probe channel?
Probe channel identification is set to Auto by default (this setting can be defined on the
BSMS service Web under the menu VT Configuration ).
Normally, there is a single heater device in the BSVT configuration, and the mapping is
therefore evident. Configurations for flow NMR applications can be handled automatically
as well - additional heaters are connected via specific VT adapters, and the remaining
active channel can therefore be considered as the probe channel. In applications with
several VT adapters of the same type (e. g. specific MAS configurations with separate
heaters for VT, bearing and rotation) it may be necessary to give an explicit definition of
the probe channel.
• How is the VT power represented in the new BSVT?
Inside the BSVT the VT power is represented in Watt (absolute power). However, the user
can select alternatively a relative representation for the GUI (percent). In that case the
reference power is the highest possible power that can be achieved with the connected
probe and the maximum voltage (48 Volt) of the VT power supply. Example:
– Cryo Probe heater with 48 Ohms: Imax = 1 A, Pmax = 48 Watt (= 100%)
• Has the maximum VT power setting an influence on the Self Tune?
The Self Tune is no longer affected by the maximum VT power (if it is high enough), since
the required power for Self Tune is evaluated in the beginning of the tuning automatically.
If the power limit is set too low, then the Self Tune aborts with a corresponding error
message (similar case if the chilling is not sufficient to reach the target temperature). The
temperature control process is not stopped in case of too restrictive power limitation (or
insufficient chilling), it is simply indicated in the regulator status that the heater power
limitation is too strict or that the chilling is not sufficient.
• Do I still need the cable Z13874 with VT power attenuator (with heat spreader) for
CryoProbes?
For operation of the former Variable Temperature control systems (e. g. BVT3000,
BVT3200) with CryoProbes, it was necessary to insert a power attenuator between the
BVT and the heater of the probe. The user could select between
Low = 10%, High = 50%
and ET = 100% resulting VT power at the probe. With the new BSVT, this attenuator is no
longer used, since the VT power is provided by the BSVT in high resolution down to
smallest values and therefore also appropriate for direct operation with CryoProbes.
Problems with overheated attenuators or full power values varying with the selected power
range at the attenuator are eliminated with the BSVT.