Increased AP density in enterprise WLANs leads to increasing RF interference and decreasing performance. An important step towards mitigating this problem is to construct precise RF maps in the form of a conflict graph. Prior work on conflict graph construction, mostly using bandwidth tests [17], suffers from two problems: a) It is limited to static settings and cannot support mobility, and b) It incurs significant measurement overhead and must be performed offline (e.g. overnight). An alternative to bandwidth tests is "micro-probing" [4] that operates on millisecond-level time scales. Micro-probing rapidly constructs the conflict graph even while the network is in use (i.e. online). While interesting in principle, micro-probing has only been evaluated in simulation. In this work, we empirically study microprobing on a 40-node wireless testbed. In doing so, we not only show that micro-probing is in fact practically realizable, but also present key insights that drive the des...