How do you measure or calculate the work of HR - most of the times HR function will be Ad-Hoc and intangible

On what terms the HR work will be calculated. As most of the times HR function will be Ad-Hoc and intangible.
Though goals will be set, KRA will be set, how do you measure if those goals, KRA's are met. How do you calculate it is met.
I would like to know how your company measures or assess the work done by a HR, can be in multiple verticals like Operations, HR Business Partner, Generalist, TA.
Do you have any kind of sheets where and how its calculated or any method to calculate.
I would also like to know how do you manage the HR's who is working from home remotely.(Timesheets for HR's)
If you have any ready references will be appreciated.

Dear Ramya,
You have written that "As most of the times HR function will be Ad-Hoc and intangible." However, this is a generalisation. Yes, it is true but for those who handle the basic or service functions of HR.
While measuring HR's work, the prominent factor that needs to be checked is what was increased or decreased because of the HR intervention. Any HR intervention should focus on:
a) The decrease in the consumption of the resources
b) The decrease in process turnaround time of some process
c) The decrease in the cost of the operations or any other cost
d) Increase or decrease of some ratio
The No 1 measurable activity in HR is employee training. Have you measured the effectiveness of the employee training?
Thanks,
Dinesh Divekar

Dear Ramya,
Is this a question raised for your MBA assignment or your final project?