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#import "@preview/unify:0.8.1": qty, qtyrange
= Mechanical specifications <mechanical-specifications>
== Modules <modules>
=== Cassette <cassette>
==== Shielding and construction <shielding-and-construction>
To achieve metrologic tier precision, modules must be fully shielded from
external interference. The only entry points for noise are:
- The DB-25 and BNC connectors at the rear, which connects via a shielded cable
to the power distribution board
- The banana jacks at the front panel, which include input protection circuits.
Modules must also not pollute neighboring modules with internally generated
noise (such as PWAM oscillators). For this reason, all modules are enclosed in
individual steel cassettes.
We chose steel instead of aluminum, as it has better shielding properties,
especially in terms of magnetic shielding.
#figure(
table(
columns: (auto, auto),
table.header([*Parameter*], [*Value*]),
[Material], [DC01 cold-rolled steel (EN 10130)],
[Thickness], [$qty(1.2, "mm")$],
[Finish], [Matte black powder coard (RAL 9005), all surfaces.],
),
caption: [Cassette construction parameters],
) <table-cassette-construction-parameters>
==== External dimensions <cassette-external-dimensions>
#figure(
table(
columns: (auto, auto, auto, auto),
table.header([*Dimension*], [*Value*], [*Tolerance*], [*Note*]),
[Panel height],
[$qty(177.8, "mm")$ ($qty(4, "U"), qty(7, "inch")$)],
[$plus.minus qty(0.1, "mm")$],
[Full rack unit height],
[Grid pitch],
[$qty(38.1, "mm")$ ($qty(1.5, "inch")$)],
[N/A],
[Theoretical center to center spacing. Two columns of banana jacks ($qty(0.75, "inch")$ grid).],
[Panel Width],
[$qty(38.0, "mm")$ ($qty(1.5, "inch")$)],
[$+0.0 "/" -0.1 "mm"$],
[Undersized to accomodate paint thickness and thermal expansion.],
[Body height], [$qty(165.1, "mm")$, ($qty(6.5, "inch")$)], [$plus.minus qty(0.1, "mm")$], [Fits between rails],
[Body width], [$qty(38.0, "mm")$ ($qty(1.5, "inch")$)], [$+0.0 "/" -0.1 "mm"$], [Same as panel],
[Depth], [$qty(152.4, "mm")$ ($qty(6, "inch")$)], [$plus.minus qty(0.2, "mm")$], [Front to rear],
[Lip height], [$qty(6.35, "mm")$ ($qty(0.25, "inch")$)], [N/A], [Top and bottom],
),
caption: [Cassette external dimensions],
) <table-cassette-external-dimensions>
The panel lips extend above and below the cassette body to fill the full
$qty(4, "U")$ rack opening while the body fits between the chassis rails.
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