How to check a SCR with digital multimeter?

Practical Commutation Circuit OF SCR

SCR control with Arduino - Half-wave controlled rectifier

Problem 4: Latching currentA. In the SCR circuit shown in figure below, the SCR has a latching current of 50 mA and is fired by pulse of length 50 µsec.Show that without resistance R, the SCR will fail to remain on, when the firing pulse ends and then find the maximumvalue of R to ensure firing.B. Show that without resistance R, the SCR can be turned on when the firing pulse width increased. Find the minimum valueof pulse width to ensure firing.100 Veeee20 ?R0.5 ?