The batteries should be in a separate, sealed compartment to prevent leaking batteries from corroding the instrument's electronics.

The working life of the batteries should be at least 80 working hours.

The display should be visible under all lighting conditions.

The reading should be held when the probe is uncoupled from the material.

There should be an indicator of proper coupling  and signal strength.

The instrument should be sealed from moisture and dirt.

The warranty should be at least two years and honored by the seller.

Repair and Calibration Service should be available in one week or less. One day Emergency Service should also be available.

Probes should be available for all potential applications that you might have.

Find out who is going to support your purchase - provide technical advice, warranty, repair and calibration services.

Check service provider's track record. You will be around for a while, will they?

Ask for references within your industry.

Finally, find out if they know anything about ultrasonic thickness gauges and how they are used.  Or, is it just another gadget for them to sell?

Please note that it is important to understand that the lack of a strong signal or jumpy display may be the only indication you get of a serious corrosion problem!

When the above is encountered, don't just move the probe to where you get a strong signal. You may be ignoring a seriously corroded area.

There are a few instruments available such as the Krautkramer-Branson DM4 & DMS that offer the inspector the choice of both:

• Zero to First Echo to detect severe corrosion.
• Multi-Echo measuring for through coating thickness measurements when only moderate corrosion is anticipated.