Thanks for the reply
All the pipe in the area is steel, using 130 feet of 6" steel well 
casing as the ground point. I would think the gas movement in the area 
would not be an issue. After 3 feet of 1.25" pipe which goes 
underground, the pipe does transition to PVC pipe. For the Measurement 
specialties sensor, it has a stainless steel body that is threaded to 
the steel pipe. There is no shield on the cable, just the 3 wires in a 
sheath. The Freescale sensor is a plastic body, with pins sticking out. 
The brass pipe screws into the steel pipe, but other than that, I have 
not shielded the wire. The service area is very low electrical activity, 
just a little cabinet heater and 2 heat trace on the pipes in a small 
aluminum enclosure. The sensors are mounted to 1/4" steel or brass pipe 
at least 6" long with a 1/4  turn valve.

The PIC and everything connected to it is isolated. Power is a wall wart 
with a DC power connector at the aluminum box that the  PIC is in. The 
box is hard bolted to the pipe. The PIC output is fiber optic 62.5/125  
cable.



Alan B. Pearce wrote:
>> The usage is natural gas, 50 PDI. max., the gas has a water
>> vapor near freezing, and the water in the well is salty.
>>     
>
> Sounds to me like the gas movement in the pipe is producing high voltages 
> that then produce ESD type arcs.
>
> The description on your sensor mounting, it sounds like there is no metallic 
> housing that could be grounded to trap ESD events due to the gas motion, or 
> weather conditions. I would be tempted to wrap the sensor in an aluminium 
> foil shroud, and use shielded cable to a suitable grounding point. 
>
>   
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