Thanks Nitin. Since, it is duration field with the same name and it is split in hours, minutes and seconds. 

I just need to find way to extract values based on the ID. Any suggestions?

<input type="text" class="form-control ng-valid ng-dirty ng-valid-parse ng-not-empty ng-touched"
id="dur-hours-u_start_date_of_activity" ng-model="parts[unit]" ng-disabled="field.isReadonly()"
ng-change="updateDuration()" title="Hours" role="textbox" aria-invalid="false" style="">

<input type="text" class="form-control ng-pristine ng-untouched ng-valid ng-not-empty"
id="dur-minutes-u_start_date_of_activity" ng-model="parts[unit]" ng-disabled="field.isReadonly()"
ng-change="updateDuration()" title="Minutes" role="textbox" aria-invalid="false">