Here's what Truetone say about the 1 SPOT mA Meter Pedal Power Measuring Device:
The 1 SPOT mA Meter (that’s “milliamp meter” for all you non-engineers), is a simple device for measuring the power consumption of your guitar pedals.
You’re probably used to seeing power supply outputs with ratings like “100mA”, which is the maximum that output can provide for a pedal. And you might have wondered whether it was enough to power your particular pedal(s). The mA Meter answers that question for you by showing exactly how much current your DC powered pedal really needs*.
No more scouring the Web for information about your pedals that might not even be accurate. Just plug your pedal into the mA Meter and see for yourself how much power it needs!
And as an added bonus, we’ve even thrown in a cable tester as part of the mA Meter… perfect for those last second cable checks at the gig.
* Input voltage range: 9-24Vdc; Max current displayed: 999mA