SCB20
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9 SCB20
9.1 Introduction
The SCB20 (Shim Control Board) is the unified and highly integrated Shim Current Source.
One single SCB20 can drive a BOSS1 configuration and two SCB20 are required for all other
Shim Systems e.g. BOSS3.
There is exactly one standard version of SCB20, which provides the necessary performance
and precision for all possible variants of connected Shim Systems.
Low level hardware functions are implemented directly on the SCB20, whereas higher level
functions such as BOSS file handling, Auto Shim and RCB Shim are provided by the
Software running on the ELCB.
It is possible to store a complete BOSS file on the nonvolatile memory of the ELCB. For
BOSS1 Shim Systems there is a predefined BOSS matrix, which does not need to be
downloaded.
The current sources of the SCB20 are unified - each current source provides a current
ranging from -1 Ampere (-130‘000 current units) to +1 Ampere (+130‘000 current units).
Since exchanging of Shim settings with the TopSpin application (command rsh and wsh) is
based on currents, it is not possible to transfer the former SCB7/13 Shim settings directly to
the new SCB20 boards. It is however possible to enter manually all shims values (Z1, Z2, ...)
that are also stored in the TopSpin shim files.
9.2 Technical Data
Parameter Min. Type Max Unit Notes
Output Current (continuous) -1.0 +1.0 A
Current Value, Resolution and
Step Size
20
2
Bit
µA
Maximum Offset +/- 20 µA
Gain Error 0.5 % 1)
Maximum Offset Drift +/- 1 µA / °C
Gain Drift < 11 ppm / °C
Tolerated range of connected
Shim Coil resistance
0 15 Ohm
Required power supply voltage
|VCC| and |VEE|
20 26 V
Sum of all shim currents
(sum of absolute values)
6 A 2)
Small Step Response time
(Transition from -100 to 100 mA)
20 ms 3)
Large Step Response time
(Transition from -1 to 1 A)
160 ms 3)
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