How to tell if tank heat pads work ?

[porthole]

I use this. Mine is a bit older and lower range, but it will read up to 400 amps DC.


https://www.amazon.com/Sperry-Instruments-DSA540A-Function-Snap-Around/dp/B00279P6C4?th=1&psc=1


Another meter i use is this one.
This is typical of a meter that the leads are put in line of the circuit to read current draw.

But many meters like this are limited to 10 amps or less

https://www.amazon.ca/Ancor-Marine-Grade-15-Function-Products/dp/B018RR9O8G

[porthole]

On a standard multi meter you switch one of the leads to the current side.
In this picture the leads are set to read voltage.

If you move the red lead to the far left port marked ‘A’ you can read the current draw.

Also keep in mind - although the clamp on meter is easier to use, the positive and negative wires need to be separated when clamping around the wire.

Look before you buy. If you are going to purchase new, may as well get one that can read AC and DC amps.

[porthole]

Couldn’t load the picture in the last post.