If you have opportunities with 0$ and have your logs spammed with the following FATAL error
[FATAL] Exception evaluating expression in SetValueAction, ifElse(isNumeric($amount), currencyDivide($amount, $base_rate), "") : Division by zero
once a field calculation is triggered, you can fix it with the following formula on Opportunities -> amount_usdollar
ifElse(and(not(equal($amount,0)),isNumeric(toString($amount))),currencyDivide($amount,number($base_rate)),0)
Bonus:
Opps with 0$ have this displayed in record view and reports from now on (were blank before) :-)
Bests
Björn Canales