How to calculate temperature adjusted maximum Zs values

[mick525]

Hello,
I have my practical 2391 test on Friday and have been told by the examiner that we will be required to complete the calcuation for the maximum operating temperature for Zs. I am unsuse what to do with the calculation.

From guidance notes three (second example down, pg 113), it shows the following equation. I cant seem to come to the final result that they do:


Ztest (max) = 1/1.20 {7.67+0.35 (1.20-1)}
Ztest (max) = 6.45 ohms


I come out with 6.65 so I am not sure where I am going wrong, can anyone help please? If you can, can you also list how to do it step by step on a calculator. Please note, I know I could use the rule of thumb method, but the examiner has specified to calculate using the method above.


Cheers

Mick

 

[tony mc]

Best of luck but take your time

READ then re READ the question knowing what they are asking before putting your pen on the answer book.