problems callibrating after extending probe cables

[shutterpunk]

I am in the process of installing 3 GHL P2exs. I have extended the cables for the probes and although im only calibrating the pH probe at the moment i am having trouble. I run through the calibration but when finished the value jumps between 10.5 and 3. The ADC numbers both read 165 so i imagine this is the source of the problem however the total cable length is around 3 metres... is this the problem and if so can it be solved?
Thanks
Rob

 

[Matthias Gross]

is calibration OK when probe is connected directly?

 

[shutterpunk]

yar, it does. I traced the problem to the cable which was faulty and although it does take a while to calibrate it gets there eventually. I am curious is there a maximum cable length for any of the sensors?

 

[Matthias Gross]

up to 8m is usually no problem, but depends on possible electromagnetical noise there
if the extension cable is defective:
- contact your retailer
or
- maybe you can crimp new BNC connectors on it?

 

[shutterpunk]

New terminals all done. We now have several probes extended to 10 metres and all readings seem to be stable and accurate after recalibration. We made up our own BNC cables using similar spec cable to that supplied by GHL.

 

[H20ENG]

I have a similar question about the type of cable used for pH & ORP probes. Is there a given spec? At work we have lots of small cable and BNC connectors / crimp tools, but it is all used for video, so I believe 75K.

Shutter,
Can you tell me the cable data of what you used? Thanks!

 

[Matthias Gross]

since it is not a HF-signal the cable type doesn't matter

 

[H20ENG]

Thanks