GM tube wires

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5 years 1 month ago #3182 by Timo70
GM tube wires was created by Timo70
Hi, how long can high voltage connecting wires be? I'm planning to install SBM-20 Tube outside, under plastic gutter (With good enclosure) so leads must be about 4-5 meters long.
Should wires be well shielded, maybe coax? Can long wires cause any problems?

Counter is Arduino based kit.

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5 years 1 month ago #3185 by Juzzie
Replied by Juzzie on topic GM tube wires
Hi there! I think there is a high risk of interference and false counts at such a length. Tube capacitance will be higher.
I've even had issues with 1m.
Maybe its better to use a long usb cable or a BT module?

Owner and operator of "southofhobart" monitoring stations.

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5 years 1 month ago #3196 by Timo70
Replied by Timo70 on topic GM tube wires
Ok, so the long hv wires is not an option.
Just have to made good water and moisture tight box for whole assembly..

Thanks.

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5 years 1 month ago #3200 by Bert490
Replied by Bert490 on topic GM tube wires
If USB distance gets too long, an audio cable to a microphone input will work (shielded pair).

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5 years 1 month ago #3201 by Timo70
Replied by Timo70 on topic GM tube wires
Ok, thanks.
I think i will try 5-10m USB active repeater cable.

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4 years 11 months ago #3348 by Sonarflash
Replied by Sonarflash on topic GM tube wires
Sorry that I didn't read this post sooner. As our friend from Tasmania says, long HV leads can be a problem and pick up interference. Not even coax will prevent a voltage drop if the cable is too long, but I suppose that can be compensated for by ramping up the voltage a bit. My GK+4 GC puts out around 390 VDC. Originally, it came with a 1 metre long cable. That was shielded inner twin-lead with push-on connectors at either end. That works well with a LND7317 pancake detector. My Aware Electronics RM-80 has the HV and GM pancake integrated inside an ABS box. This can be put in a plastic bag if I want it outside. This detector head with the HV is connected to the computer 9 pin serial port or a USB-MSP430 interface module via a 4 lead telephone cable. There is a socket on the RM-80 for a standard 4 lead telephone connector. If this detector head is located a distance from the computer, they recommend a separate power pack (5 to 9 VDC) at the detector head. I had no problem running this unit on a 50 foot telephone cable inside my room. Their detector head develops a healthy negative going pulse witch trips the RI pin 9 serial port, or is recorded on the USB-MSP430 module, which is in turn connected to a lap-top.
You might get away with using several metres of inner twin lead shielded cable, like audio cable, by making certain the shielding has a good earth ground, kind of like what hams use for their antennas. You might also try placing the SBM-20 and electronics together in a plastic enclosure, then run a cable to your computer. Since USB cables have limits on their length, you will probably need a USB extender for that kind of arrangement.
I'd like to hear how your system works out.Drop me a note at:
This email address is being protected from spambots. You need JavaScript enabled to view it.
Brian, VA7BDG

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