how do you calibrate it?

Calibration is not needed as far as I know

Placing on diamonds and having no response, what does that mean?

I have used this unit and had the same response on known diamonds. Sometimes the stone is dirty and needs a cleaning. This can throw off results. Also, my unit is getting returned when I have a suitable replacement. It sometimes takes 3 or more tries to get it to register. Clean the stone and try touching it with a firm but not point grinding pressure a few times and if it doesn't work try another tester. Assuming of course you know the diamond is real.

Model Number	PMuT III
Package Dimensions	20.1 x 8.4 x 5.9 cm
Color	Black
Power Source	Battery Powered
Package Weight	0.17 Kilograms
Batteries Required	No
Batteries Included	No
Brand Name	PRESIDIUM
Country of Origin	Singapore
Item Weight	97 Grams

Precidium Multi-Tester II

Description

Specifications

Common Questions