Not a TriMetric, but for $20 might be worth trying out...
Bayite DC 6.5V-100V Digital ammeter voltmeter Amazon suggested this for me and I'm thinking for $20 I might just give it a try. Has very good reviews too.
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No problem with the shunt in line with the frame ground
Just so there are no other power carrying ground/negative wires connected at the battery
Just so there are no other power carrying ground/negative wires connected at the battery
