Thank you Paresh. Both the discussion thread and link are helpful.
I found a soil moisture meter with display with NPK level detection as well from a company called Gaby In India itself. This is a hand held device. I will be updating my experience using the same after we complete the trails for any anyone who is interested. 

Hello Hiranya.
A colleague of mine who is working on developing a low-cost instrument to measure soil moisture opines that the same instrument could be used to measure moisture content in sludge provided it can read from 0-100%. 

I'd also bring to your attention this thread regarding  Faecal Sludge Field Laboratory - Discussions . The list of equipment for a FSFL includes this:  Soil Moisture Sensor Vernier SMS-BTA www.vernier.com/products/sensors/sms-bta/

Hope this helps.

Best
paresh

I am looking for a moisture content sensor/meter that would help me in monitoring the sludge moisture content daily while the sludge is on the unplanted sludge drying bed. Hence it should have a large window range of max and mini moisture content level sensitivity. I am from Bangalore, India. Any contacts of suppliers or any product details would be really helpful inorder to conduct my experiment. 
Thanks in advance.