Hello

I have bought this:

DROK® Digital Multimeter DC 6.5-100V 20A Voltage Amperage Power Energy Meter DC Volt Amp Testing Gauge Monitor LCD Blue Backlight Digital Display with Built-in Shunt

I am converting a van to a campervan and have wired up a 12v 190ah leisure battery system with a 230v charger and also a solar panel. I have a solar controller which is 20a and everything is working fine. I have a fridge, lights, TV, diesel heater, usb chargers and mini fans. I would like to measure my power usage in amps. Particuarly when the diesel heater starts up. How do i wire this up to the system? I just want to know the status of my battery and what power it is using at any given time. I am not interested in what the solar panel is doing.

Can you give me a BASIC wiring diagram or explanation in SIMPLE ENGLISH! Many Thanks