app/views/shared/meter_attributes/_symbol.html.erb
<% if field.allowed_values.empty? %>
<%= form.input field_name, as: :string, input_html: {value: value}, required: field.required?, label: label.try(:to_s).try(:humanize), hint: field.hint %>
<% else %>
<%= form.input field_name, as: :select, selected: value, collection: field.allowed_values, include_blank: true, required: field.required?, label: label.try(:to_s).try(:humanize)%>
<% end %>