megger 1720

[ccfc]

Dont know if anyone is aware of this but new megger 17 range does not like checkboxes if you performe a no trip loop check at local plus 1 ohm it wil give you a extremly low reading, with my 1720 & socket & see cb300 about .30 ohms. Ask megger why guy told me it was not just s and s but all checkboxes at a low test value on no trip setting anything under 10 ohms test value.

 

[steptoe]

:slap

megger strikes again with their accurate readings then I assume!!!!!

 

[ccfc]

No ok readings at local ie socket with no checkbox its just for some reason the way it tests no trip does not like the electronics in checkbox at plus 1 ohm all other tests ok?

 

[steptoe]

checkbox or cable length, resistance is resistance,

megger is rubbish, is rubbish, same thing.

 

[batty]

Whats a checkbox?

 

[ISSWWW]

Ask the same person you spoke to at Megger why they took thier own check box off the market for ages after the release of the 1700 series?

After some redesign it now is back on the market and apparently work well with the new range.

 

[ccfc]

True mark but was told there new checkboxs lowest setting for loop test would be 10 ohms

 

[Terry W]

Whats a checkbox?

I assume http://tiny.cc/13ma2

 

[batty]

Thanks

 

[user 4716]

checkbox or cable length, resistance is resistance,megger is rubbish, is rubbish, same thing.

Actually low cost check boxes add pure resistance and cables have impedence which has a resistive part and an inductive part.

So adding a 1 ohm resistor to a loop reading is not the same as adding 1 ohm of cable.

 

[Doc Hudson]

Actually low cost check boxes add pure resistance and cables have impedence which has a resistive part and an inductive part.So adding a 1 ohm resistor to a loop reading is not the same as adding 1 ohm of cable.

I am not sure I agree entirely with that statement. I fear it may confuse some student members. To clarify I would say. The typical cables we use are constructed of copper or aluminum which have a fixed resistance per meter, (at a given temperature), and the resistance tables are given in the back of the on site guide. However these resistance values relate to dead testing, (at 200C) to obtain R1+ R2 values. The impedance element comes into effect when testing at AC voltages e.g. whilst doing the live earth loop impedance test. So a coil of cable in the back of your van can be very much a resistive equivalent but connect it to a live circuit and other factors now come into play.

Doc H.

 

[Sidewinder]

Cables also have capacitance which will also have an affect on the readings on them.

Also, I'm not sure what frequency the test meters use.

Hopefully 50Hz, though that would be no good for someone working on 60 or 400Hz as the readings would differ.