Up to how many SSRs can be connected to the UT?

The UT's voltage pulse specifications are: ON voltage 12 VDC or more; load resistance 600 Ω or more; ON voltage 0.1 VDC or less. For example, in the case of the Omron G3PH (operating voltage DC4-30 V, input current 5 mA or less), up to 4 units can be connected in parallel. To drive an SSR with the UT, use voltage pulse output. Since the current flowing will be 12 V/600 Ω=20 mA, this satisfies the above conditions.