Low signal for a flame rod (application: Pilot for a process burner)

[Saver2008]

Hi!

I have the following situation:
I have a pilot which we added a flame rod (kanthal material)for detection flame. The flame rod is crown rod and the flame relay is the fireye MBPF-1001. The problem that I have is when we connect (belden wire) the MBPF-1001 to the flame rod "spark plug or plug"for a between them of 1 meter, there is signal and it is indicated on MBPF-1001 but when we measure with a volmeter the current is zero.
Then we make the same exercise but with a distance between flame rod and MBPF-1001 of 20 meters, there is no signal on MBPF-1001
and also the current measured is zero.

We suggest that flame form and intensity of the pilot is not high but still we have our doubts.

Any ideas of this situation....will be welcomed.

Thanks

Rolander

 

[Crowbar1]

Your flame signal will be in the µA (micro-amps) range, that could explain your signal loss at a greater distance according to the Fire-eye data sheet:

The wire type and its capacitance (picofarads or microfarads) to ground may cause low signal problems,
so a grounded shield may decrease the signal due to the cable's internal capacitance. Multiple UV
tube-type sensor leads run together without shielding may interfere or "cross talk", so the shield or
flexible armor must be grounded to prevent this situation. For flame rod sensor runs approximately
100 feet (30 meters) or greater, use Belden P/N 8254-RG62 coax cable. To achieve the maximum
wiring distance, the shield should not be grounded (keep in mind that an underground shield provides
less protection against electrical interference). Depending on field connections, sensor wiring
can be up to 200 feet (61 meters).

You may still have an issue with your pilot burner if your flame signal is marginal to begin with.

Rich