# How to route a nasty signal (200V/µs)?

I have to route this signal for a distance of ~70mm through a dense (mostly digital) 2-sided board. The signal is generated externally and I have no control over its shape, it's basically a pulse train at around 30 Hz, where each pulse is 10µs long, 200V in amplitude, and the front is particularly strong, it attains the 200V within a µs.

This signal is either measured via a high-value resistive divider, or shorted to ground through a relay:

simulate this circuit – Schematic created using CircuitLab

The current when shorted is ~1.5A. The signal is at ground potential in the other 99.97% of the time, and I'm taking care to switch the relay during that quiet times, to prevent sparking.

The red-shaded part is what worries me (btw I don't actually have a fuse, I inserted it so I could separate the nets, otherwise Circuit Lab paints all in red).

How can I route this signal so that it doesn't cause excessive EMI?

1. On the PCB, coplanar waveguide style (sandwiched with GND in every direction),
2. On the PCB, just as far away from other signals as possible,
3. On a separate wire (probably shielded), physically separated away from the board,
4. Something else?

EDIT: - shortening this distance is not very feasible.

• What impedance is it? Why is it important to measure the amplitude? Commented Jul 26, 2018 at 5:56
• The amplitude is unimportant, I only want to measure the frequency, as it is somewhat variable. Commented Jul 26, 2018 at 6:27
• Dos that mean that you could leave it shorted all the time if you could measure the frequency another way? In that case don't measure voltage amplitude but current of shorted signal.
– Curd
Commented Jul 26, 2018 at 7:56
• Use a shielded flying wire, it will save you a lot of time. Commented Jul 26, 2018 at 9:28
• Does that mean you could use a 20V pulse instead of 200V? or is it inductive and you want to measure capacitance or? Commented Jul 26, 2018 at 10:49