If you have a power supply that doesn't have any gauges on it, and you wanted to come up with a way to keep up with how much current was being drawn and what sort of voltage drop you was getting. Then you come to the right place - MICTUNING LCD Digital Display Ammeter. It combines 4-in-1 functions: Voltage, Current, Power and Energy measurement. It's a good choice to those who like to be able to keep track of data. 
With this, Now you can see what the instant voltage is, current draw, wattage, and the amount of energy taken in. It can be used in many scenarios, for example, installed this in your campervan so you can monitor the charge in the battery and see which devices are drawing current and how much. This gives a reading of voltage, current draw, watts and watt hours. It seems very accurate and enabled you to keep a very close eye on the battery. It gives you the reassurance without worrying about the battery too much. Or used this brilliant ammeter to monitor the leisure battery in your motorhome. When turning on various appliances in the motorhome you can see exactly how much power it uses.
The Ammeter also features with Voltage Alarm Function. The backlight and voltage value will flash simultaneously if the testing voltage is beyond alarm threshold (6-90V factory alarm value), and it can be set if needed. Furthermore, it can automatically store the last testing data when suddenly powered off and the energy value can be reset by a short press after long pressing the function button for seconds.
Something you will love is that it has an LED screen. The screen is easy to see in the day and the blue back light makes it nice in low light. Even a dim backlight can overwhelm the darkness in an RV at night. Comes with a high power shunt rated at 100A, it can handle large range measurement. Very easy to install with clear and concise wiring diagram printed directly on the back of the item.
Conclusion:
This is a great gauge for measuring Voltage, Current, Power and Energy, which tells you how much power is in your batteries, how many amps and watts you're using and how many amp hours you've used. The screen is large enough so that all of these things can clearly be displayed at once. In a word, MICTUNING LCD Digital Display Ammeter is very useful to anyone wanting to keep track of their battery usage.