Recent in-chamber work on ETMY has provided a OSEM PD RMS trip level comparison between the Hardware watchdog (HWWD) and the IOP software watchdog (SWWD).

We have verified that the two systems have very similar trip levels. The SWWD trip level is hardcoded at 110mV. The HWWD level can be modified, but it is running at its default of 110mV.

The plot shows: the PD RMS status for the SWWD (Ch 4, GOOD=1, BAD=0); and the HWWD (Ch 2, GOOD=0, BAD=1). Also shown is the SWWD RMS monitor for the ETMY top stage OSEM, SIDE channel, which is the channel driving the RMS errors.

As can be seen, Ch4 and Ch 2 match each other very well.

Note that the maximum time in error in this plot is only 3 minutes. If the excitation were to extend to 10 minutes the SWWD would have tripped the SEI DACs, and if it were to extend to 20 minutes the HWWD would power down the ISI coil drivers.