Rising IR reading

[Bangell]

Hi , I'm a newby to the forum and would like to know if anyone can tell me why on some IR measurements the figure starts out relatively low(300k) then very slowly rises to 900k or so. Leads are new and tight.

Thanks.

Brian

 

[samson337]

Damp in the cable

 

[Manator]

Welcome to the forum.

You should look at it just like you would filling a bucket with water, it takes time to fill to the level you need.

Ahh just re read the OP, a slowly rising reading could indicate damp conditions,particulary common on newly chased and plastered walls.

 

[betty swollocks]

^^^ +1 ^^^

 

[kme]

At the end of the day - does it matter if your reading rises to 900Kohm or so?

That isn`t going to be an acceptable result - can be a result of a capacitive effect, or a drying damp condition......would need more info - although It is going to need investigation, IMO.

KME

 

[Doc Hudson]

Hi , I'm a newby to the forum and would like to know if anyone can tell me why on some IR measurements the figure starts out relatively low(300k) then very slowly rises to 900k or so. Leads are new and tight.Thanks.

Brian

Welcome to the forum, I have moved this thread to the student area. You would need to be thinking back to your electrical science theory teaching. Try considering the effects of capacitors in circuits where charges can rise and decay. Then remember that a capacitor is two parallel plates separated by a dielectric (an insulating material).Then think of a PVC T&E cable, two parallel conductors {plates} separated by a dielectric {insulating material}. Remember that your IR tester is generating a DC voltage and probably measuring the current flowing to calculate the resistance. A capacitor blocks DC, so as it charges the current flow will gradually decay. A known voltage with a decaying current would imply a rising resistance proportional to the rate of decay of the current.As has been said numerous factors affect this, size of conductors, length of cable, damp, other accessories still in circuit, etc.

Doc H.