sidac parameter
A SIDAC is realy a thyristor. Thus, it will trigger at a certain voltage and remain in conduction until the current through it drops below the hold-up current.
To test, apply an increasing voltage to the SIDAC, through a resistor. At a certain voltage the SIDAC will turn on. This is a parameter that you need, so measure it carefully.
The current limiting resistor should be high enough such that the resulting current through the SIDAC is lower than the maximum continuous current, but low enough to ensure the current will be higher than the hold-up current, so the SIDAC will stay on.
Once the SIDAC has triggerred, measure the current through it and increase the series resistor until the SIDAC turns off. The current at which the SIDAC turns off is the hold-up current.
Repeat these tests for the other polarity.