Measuring R2.

[EdwardCurrent]

Hello,
When measuring R2 using R1 + R2, if the conductors are different sizes, (ie) 2.5mm and 1.5, or 4.0mm and a 2.5 earth, how do you work this calculation out please ????
Cheers,
Ed.

 

[comms]

If your measuring just R2 use a wander lead. Connect wander lead to one end of cpc take the meter with other lead and connect to other end of cpc take reading. Dont forget to null the wander lead & meter prior to undertaking R2 test or measure the resistance of the meter wander lead & deduct from the test result.

Better to do R1 + R2 then result can be used to confirm / workout (for pir) Zs of circuit.

 

[EdwardCurrent]

Cheers Comms,
A wander lead is out of the question in this case, I do understand what you are saying though.

Ta, Ed.

 

[Spark123]

Just out of interest, why do you need R2?

 

[dingbat]

Hello,
When measuring R2 using R1 + R2, if the conductors are different sizes, (ie) 2.5mm and 1.5, or 4.0mm and a 2.5 earth, how do you work this calculation out please ????
Cheers,
Ed.

Some confusion here, Ed. You can measure either R2 on its own or (R1 + R2) together.

Are you asking how to calculate R2, having measured (R1 + R2)?

If so, the ratio of resistances is in inverse proportion to the ratio of CSAs, so R1/R2 = CSA2/CSA1.

You should be able to work it out from there... if not, back to Key Skills classes for you!

 

[ebee]

Example.
a 2.5/1.5 T & E cable.
R1 + R2 = 0.4 ohms
R1 = 0.4 x 2.5/1.5 = 0.24
R2 = 0.4 x 1.5/2.5 = 0.16

 

[securespark]

A wander lead is out of the question in this case

Why???

 

[EdwardCurrent]

Hello,

Thank you for your help on this.

The circuits my collegue measures are usually in shops etc where a 'fly lead' would cause too many problems for the unsuspecting 'public' !

He needs the R2 reading for MW cert's.

Once again thanks.
Ed.

 

[RF Lighting]

MEW certificates ask for R1&R2 or R2.

You only need to complete one column.

 

[ricicle]

Example.
a 2.5/1.5 T & E cable.
R1 + R2 = 0.4 ohms
R1 = 0.4 x 2.5/1.5 = 0.24
R2 = 0.4 x 1.5/2.5 = 0.16

Wrong - R1 = 0.16 R2 = 0.24

 

[ebee]

Sorry I got them transposed, you are absolutely correct.
Good to see that someone`s taking notice

 

[ricicle]

Sorry I got them transposed, you are absolutely correct.
Good to see that someone`s taking notice

And I'm watching the footy at the same time

 

[ebee]

I`m glad you did (Not the footy I`m not a fan - Sorry) but I`m glad you checked me out and corrected me, Ok I did it this AM before rushing out to work in the hope of helping someone out but did not double check what I`d done, no excuse just glad you were there to double check my error

 

[ricicle]

I`m glad you did (Not the footy I`m not a fan - Sorry) but I`m glad you checked me out and corrected me, Ok I did it this AM before rushing out to work in the hope of helping someone out but did not double check what I`d done, no excuse just glad you were there to double check my error

No probs

 

[EdwardCurrent]

Hello RF Lighting,

He uses Robin certs, no R1 + R2, only earth continuity.

Cheers.
Ed.