The channel table

Every test carries one: the list of what was plugged in where, what it measures, and what its calibration says. Visual Dynamics treats it as what it is — a spreadsheet — so it imports from and exports to .xlsx, and behaves like every other table in the window.

What it is not is a free-form sheet. Every column says what it holds, which is what lets a column have rules about its own contents: a direction can be a drop-down because there are exactly twelve of them, a unit can be narrowed to what the channel measures, and an expiration can offer a calendar.

The columns

column	holds
Channel	the number the hardware reports. Positive, whole, and unique — it is how a row is identified, so two rows cannot claim one number
Node	the node it sits on. A whole number, or blank when nobody wrote it down
Direction	one of X+ X- Y+ Y- Z+ Z- and the six rotations
Role	reference (it drives), response (it answers), or monitor (recorded, judged as neither)
Control	whether the controller controlled to it. A check box
Channel Type	what it measures: acceleration, velocity, displacement, force, pressure, strain, voltage, temperature
Unit	the engineering unit, narrowed to ones the type could be in
Sensitivity (mV/Unit)	millivolts per whatever the Unit cell holds — the two are one calibration statement, which is why the header says so
Range (V)	the instrumentation's voltage limit, whole volts, defaulted to the ±5 V most hardware has
Serial Number, Make, Model	the sensor's identity, as text
Triax DOF	X, Y or Z — which leg of a triaxial accelerometer this is. Not a direction; the Direction column says where it points
Expiration	when its calibration runs out, with a calendar to pick from
Comment	anything else worth writing down

Anything else a source carries is dropped. A Rattlesnake save brings its coupling, excitation and feedback wiring along — how the controller ran, rather than what was measured — and carrying columns nothing interprets made this object a place data went to be ignored.

That is only safe because what does belong is recognised however it was spelled. Case, spaces, hyphens, a trailing colon and a parenthetical unit are all tidied away first, then the words that genuinely differ are mapped: Cal Due is the expiration, Point is the node, SN and Serial Number are the same column, and a calibration lab's Sensitivity (mV/g) lands where you would expect.

Role and Control

Role is one value rather than three check boxes, so the one nonsense state cannot be written: a channel is not both the input and the output of the same estimation. Blank means undeclared, exactly as an undeclared unit does.

A control channel is a response, and that is enforced from both directions — checking Control on a monitor is refused, and so is changing a control channel's role out from under its check. Both refusals say why, in the status bar.

A controller run declares these for you. A channel with a feedback device is a drive, which is Rattlesnake's own rule, so it imports as a reference; every other enabled channel imports as a response. And a random, transient or sine-sweep run states its control channels through its specification — the requirement is written per control channel — so those arrive already checked.

Two strictnesses

They are deliberately different, and it is worth knowing which you are meeting:

• A file is read leniently. A value that will not parse is blanked rather than refusing the whole import. Refusing would leave you nothing to fix, and this table is where you would fix it.
• An edit is refused. Once you are typing, an invalid value is rejected at entry with the reason, never written and complained about later.

So a spreadsheet full of rubbish still imports, with the bad cells empty and waiting; typing the same rubbish into one of them does not.

Merging tables

A survey acquired in passes brings one channel table per pass, and project.merge combines them (see Projects). Two rows are the same channel when everything but the channel number matches — the number is the hardware's bookkeeping, not the channel's identity — and the merged table renumbers 1..N. Rows that agree on point and role but disagree elsewhere refuse, naming the point: keeping either description silently would silently drop the other.

Round-tripping through Excel

Export… writes an .xlsx a calibration lab can fill in, and the constraints travel with it. Every column that limits itself carries Excel's own data validation — Direction, Role, Control, Channel Type, Triax DOF — so Excel refuses a bad direction there for the same reason the window does here.

The unit list follows the channel's type. Excel cannot hold a different list per row, but it can look one up: the units for each quantity sit on a hidden sheet as named ranges, and the rule is INDIRECT of the Channel Type cell beside it. Declare a channel a voltage and its unit cell offers V and mV; leave the type blank and it offers all of them.

Channel and node are written as numbers, so Excel does not flag every cell with "number stored as text", and a blank node stays blank rather than becoming a zero.

project.channel_table.dof_strings()      # ['101Z+', '107Z+', ...]
project.channel_table.roles()            # ['response', 'reference', ...]
project.channel_table.controls()         # a boolean per channel
project.channel_table.sensitivities()    # mV/EU, NaN where undeclared
project.channel_table.units_for(0)       # what the first row's channel could be in

visualdynamics.export_file(table, 'channels.xlsx', format='excel')
table = visualdynamics.import_file('channels.xlsx')