Rockstars 1989, It sounds like you already have purchased the ones in the pics but I have found that those won't read when polarity reverses (when you reverse the train). I use these on my DC G Scale layout, they are zero center and read correctly on reversed polarity.
DC Analog Volt Meter Panel Mount 15-0-15 PM15015-DC
DC Analog Ammeter 20-0-20 Amps DC MS52 type
Chris S.