## OPI Probe

With OPI Probe CSS context menu, CSS user can pass PV names to an OPI so that their PV values can be displayed in an OPI.

### How to create a probe OPI

A probe OPI is same as an ordinary OPI, except that you need to set the "PV Name" property of a PV widget to:

- `$(probe_pv)` if the probe OPI only work for one PV;
- `$(probe_pv_index)` if the probe OPI should work for multiple PVs. `index` is the index of the PVs that are passed in. For example, the widget with `$(probe_pv_0)` will have the first PV name passed in, $(probe_pv_1) will have the second PV name passed in, ...

The path of the probe OPI can be set in BOY preference page with the item `Probe OPI`. If no probe OPI is set in BOY preference, a built-in probe OPI will be used.