Q: How does a wrist bandcum footwear ground tester differ from the work station monitor? Can we not use only the work station monitor when it can monitor the worthiness of wrist strap even? And, Can we not check the worthiness of a wrist strap with a normal multimeter

A: I think that I understand your question here.  One way or another, a company needs to say what they are going to do in terms of ESD compliance.  They need to then do what they say they will do and document it.  They need to test the ESD devices.  They then need to test the testers.  And they need to show records of such in a pass/fail document and to prove that they are committed to quality and do not accept anything into the environment than will lead to a failure.

A wrist strap/footwear tester is proven and tested.  It is convenient to monitor and record the compliance to a whole shift of people in a given EPA.  But what if someone tests their wrist strap that morning and it fails at 10:25 that morning.  They won’t know it failed until later that day. 

The advantage of the constant monitor is that it not only alarms the moment it fails but it also forces the user to keep it on (wrist strap) while seated at the ESD workstation.  That’s fine.  But you need to test the testers periodically.  And to document those tests.  I hope I understood your question and answered it accordingly.

I suppose you could check the worthiness of a wrist strap with a normal multimeter.  I have a device that measures the connection from a connected 4mm, 7mm, or 10mm snap, through the coil cord and 1M Ω resistor, and two conductive cylinders that measure a stretched out wrist strap.  With it, I can measure the cuff only, the cuff and cord, or the cord only.  It cost me (us) a small fortune.  I have a Fluke 123 Industrial Scopemeter and a Fluke 77.  They are great meters, up to about 40M Ω or 4.0E7.  If you have wrist straps that are conductive enough, then great.  Good luck.  You may need a Megohmmer.