如何在视图页面中调用自己的库

My library name is numbertowords and it's in library folder and i want to call it in view page..How do i call?? i called like this

<?php
$this->load->library('numbertowords');
?>
<?php 
echo $this->numbertowords->convert_number($row['billtotal']); 
echo" Rupees Only"
?>
</h3>

I am getting error like this

A PHP Error was encountered Severity: Notice

Message: Undefined property: CI_Loader::$numbertowords

Filename: Inventory/Bill_Print1.php

Line Number: 233

Backtrace:

File: C:\xampp\htdocs\Yuva3\application\views\Inventory\Bill_Print1.php
Line: 233
Function: _error_handler

File: C:\xampp\htdocs\Yuva3\application\controllers\TipUp_Loan.php
Line: 74
Function: view

File: C:\xampp\htdocs\Yuva3\index.php
Line: 315
Function: require_once


Fatal error: Call to a member function convert_number() on null in C:\xampp\htdocs\Yuva3\application\views\Inventory\Bill_Print1.php on line 233
A PHP Error was encountered
Severity: Error

Message: Call to a member function convert_number() on null

Filename: Inventory/Bill_Print1.php

Line Number: 233

Backtrace:

changed my library file name from numbertowords To Numbertowords..

    <?php
$this->load->library('Numbertowords');
?>
<?php 
echo $this->numbertowords->convert_number($row['billtotal']); 
echo" Rupees Only"
?>
</h3>

The problem is that $this is not what you think it is.

What you're expecting it to be is a reference to the controller instance (sometimes called the "CI Super object"), but it is actually an instance of the loader ($this->load).

The library should be loaded in the controller and convert_number() used to modify data there before it is passed to the view.