What type of sensor would be able to sense an EM pulse from a device? Thanks!
coil
a simple well wound coil around the wire supplying the device with electricity should be enough , connect that to a voltmeter and set it to low range . simple .
None
If it’s real EMP, all the lights go out 
Hmm, I guess I should have
Hmm, I guess I should have clarifyed more. Say a small pvs pipe emits a EM signal/pulse. I want my robot/vehicle to get close to it. Is there a sensor I can use or am I looking at a more complex circuit of some sort. Thanks!
**hall effect sensors **
research hall effect sensors , i guess they would do you good .