GoldExI : FAQ : Spike protection

Question

Does GoldExI have any feature which protects experimental setup from sudden current/voltage jumps which may come from DAC cards?

Answer

Indeed when you use GoldExI or other Data Acquisition software, it can be not very well programmed so that it creates sudden current/voltage jumps on the DAC output.

Example 1: When you measure IVC and press DoIt button, the measurement software should set the current to the minimum value and then increase it by small increments. When current jumps to minimum the system may react in undesirable way, i.e. trap flux quanta etc..So, it is better to avoid such a possibility.

Example 2: When in measurement window of GoldExI you drag the scroll bar of any current, your mouse can by chance go too far from the scroll bar and the scroll bar (as well as corresponding current) will be set to the initial position abruptly.

GoldExI has built in protection from such abrupt changes of current. It remembers the last set value for each current and when the next value which has to be set is very different from the previous one, GoldExI sets it in several smaller steps.

Special care was taken when starting and stopping generator in the measurement window. GoldExI is programmed to provide spike free operation in this case too.

Nevertheless there are circumstances when the spikes may appear. This usually happens just after re-configuration of virtual currents (changing type of current, DAC card or channel number). It is safer to do this re-configuration when all currents are set to zero.

Spikes may also appear if you use high frequency generator with one-directional sweep in the measurement window. So to be safe, always mark [x] 2Directions inside the limits which correspond to sweep1. If such limits are not available for some measurements (e.g. R(T)) , GoldExI automatically uses two-directional saw-tooth sweep. :-) See generator description for details.

The maximum value of current/voltage jumps of the DAC output (given in DAC bits) can be set in Options | Delays | Maximum DAC step. The smaller is this value the smaller are the jumps, but the longer are delays. The recommended values for 16-bit cards is 128..256 bits, for 12-bit cards - 8..16 bits.