I purchased a pair of these panel meters to install into my Elenco XP-720 Triple power supply.  It outputs 5VDC at 3 Amps and +1.25 to +15VDC and -1.25 to -15VDC at about 1 Amp.  I’ve cut out the front panel to accommodate the meters.  They look great.  It’s just not apparent to me how to connect both of them.

The +/- power supplies share a common transformer with a bridge rectifier have a shared ground to put out 1.25 to 15VDC + and – on each side of that ground.

The meters did not come with any documentation or a manual.  Is there a manual available for these panel meters.  There is a basic wiring diagram on the amazon page at https://www.amazon.com/gp/product/B00IZTTAKO/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1.

How do I connect these meters so that one will monitor the positive 15V supply while the other monitors the negative 15V supply?  There’s another person who has done this and talks about it on Amazon at https://www.amazon.com/gp/customer-reviews/R3PERQNUVPP8QB/ref=cm_cr_getr_d_rvw_ttl?ie=UTF8&ASIN=B0002DT0GU but did not give any details of how he did this or how he connected them.  He only has a couple of photos there.

Some help would be much appreciated.