# Field Monitor
A Field Monitor is a field monitor that records selected electromagnetic field components in the frequency domain.
This object corresponds to tidy3d.FieldMonitor (opens new window).
# Name
name: Unique name for the monitor.
- Required field
# Geometry
Specification of the monitor region.
# Center + Size
Object definition through a center position and size.
center: Center of the monitor in x, y, and z-directions.
- Type: floating-point number
- Unit: m, mm (default unit), um
size: Size of the monitor in x, y, and z-directions.
- Type: floating-point number
- Unit: m, mm (default unit), um
- Constraint: greater than or equal to 0
- Required field
# Bounds
Object definition through minimum and maximum coordinate bounds.
min: Values of the x, y, and z coordinates defining the lower corner of the monitor.
max: Values of the x, y, and z coordinates defining the upper corner of the monitor.
- Type: floating-point number
- Unit: m, mm (default unit), um
- Required field
NOTE
A 3D field monitor can produce a large data storage size.
For 1D or 2D monitors, set the size of the corresponding dimensions to 0.
# Settings
# Fields
fields: Field components stored by the monitor.
- Options: Ex/Ey/Ez/Hx/Hy/Hz
- Default: all six field components
NOTE
Flux and Poynting vector data are included in the result when all necessary field components are selected.
# Frequency Points
freqs: Frequencies recorded by the monitor.
Frequency points can be entered by range or as a custom list in the frequency settings panel.
See Frequency Settings.
# Advanced
colocate: Toggle whether fields are colocated to grid cell boundaries.
- Options:
- True: Colocate fields to grid cell boundaries.
- False: Store fields at their native Yee grid positions.
- Default: True
interval_space: Number of grid step intervals between monitor recordings in x, y, and z-directions.
- Type: three positive integers
- Default: (1, 1, 1)
apodization: Optional apodization window applied to frequency-domain field data.