From 585087a049abd4e8cb43efaa58f66e169bae7a51 Mon Sep 17 00:00:00 2001 From: Denis Chevalier Date: Sat, 8 Aug 2026 17:37:00 +0200 Subject: finish mechanical specifications --- mechanical-specifications.typ | 385 ++++++++++++++++ pictures/chassis-module-loading.svg | 895 ++++++++++++++++++++++++++++++++++++ preamble.typ | 8 + 3 files changed, 1288 insertions(+) create mode 100644 pictures/chassis-module-loading.svg diff --git a/mechanical-specifications.typ b/mechanical-specifications.typ index 40cc933..ae5c04e 100644 --- a/mechanical-specifications.typ +++ b/mechanical-specifications.typ @@ -886,3 +886,388 @@ least $qty(4, "mm")$ height. Jack labels should be at least $qty(2, "mm")$ height. == Chassis + +=== Overview + +The chassis provides the mechanical and electrical infrastructure for housing +modules. It includes: +- Structural enclosure with EMI shielding, +- Cassette rail system for module installation and removal, +- Power distribution board with backplane connectors, +- Front panel with reference outputs and system controls, +- Thermal management provisions. + +This specification defines interface requirements that any compliant chassis +must meet. Chassis may vary in capacity (number of module positions), form +factor (rack-mount, desktop, portable), and mounting style. The reference +implementation (#ref()) describes a +$qty(19, "inch")$ $qty(4, "U")$ rack-mount chassis with $8$ module positions. + +=== Dimensional requirements + +#figure( + image("pictures/chassis-module-loading.svg"), + caption: [Chassis module loading dimensional requirements], +) + +==== Module interface dimensions + +All chassis must accommodate standard SAME cassettes. The following dimensions +are mandatory: + +#figure( + table( + columns: (auto, auto, auto), + table.header([Parameter], [Value], [Notes]), + [Module pitch], [$qty(38.1, "mm")$ ($qty(1.5, "inch")$)], [Center-to-center spacing], + + [Module opening height], [$qty(177.8, "mm")$ ($qty(4, "U"), qty(7, "inch")$)], [Panel visible area], + + [Module body clearance], [$qty(165.2, "mm")$], [Between top and bottom rails], + + [Module depth], [$qty(152.5, "mm")$], [Front panel to rear connector], + [Rail-to-rail width], [$qty(38.1, "mm")$ ($qty(1.5, "inch")$)], [Center-to-center spacing], + ), + caption: [Module interface dimensions], +) + +==== Capacity + +Chassis capacity is defined by the number of module positions. There is no +minimum or maximum, but the following constraints apply: + +#figure( + table( + columns: (auto, auto, auto), + table.header([Capacity], [Power budget], [Notes]), + [Per module], [$qty(185, "mA") at plus.minus qty(15, "V")$], [Maximum per position], + + [Per module], [$qty(100, "mA") at plus.minus qty(5, "VD")$], [Maximum per position], + + [Total], [Scales with capacity], [Power distribution must support all positions], + ), + caption: [Chassis capacity power requirements], +) + +Designers should consider thermal dissipation when determining maximum capacity. + +==== Clearances + +The rear clearance (behind cassette) should be at least $qty(25, "mm")$, to +account for the DB-25 connector and cable bend radius. + +=== Structural requirements + +==== Material + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Material], [Steel (recommended) or aluminum], + [Minimum thickness], [$qty(1.5, "mm")$ (steel) or $qty(2.0, "mm")$ (aluminum)], + + [Finish], [Black powder coat or anodization, conductive areas masked], + ), + caption: [Chassis material requirements], +) + +Steel is preferred for magnetic shielding. Aluminum may be used where weight is +critical, with reduced magnetic shielding performance. + +==== EMI shielding + +A fully loaded chassis must form a continuous shielded enclosure: + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Shielding effectiveness], [$gt qty(20, "dB"), qtyrange(80, 1000, "MHz")$], + [Panel joints], [Metal-to-metal contact of conductive gasket], + [Ventilation openings], [\ Maximum slot dimensions: $qty(10, "mm") times qty(2, "mm")$], + + [Cable entry], [Shield connectors or filtered feedthroughs], + ), + caption: [Chassis EMI shielding requirements], +) + +==== Grounding + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Chassis earth bonding], [All panels bonded to single earth point], + [Earth impedance], [$gt qty(0.1, "ohm")$ between any two chassis points], + [Safety earth], [Connected to mains earth via IEC inlet], + [Module earth path], [Via DB-25 shell and pin 25], + ), + caption: [Chassis grounding requirements], +) + +=== Cassette rails + +The rail system guides cassette insertion and provides retention. + +==== Geometry + +#figure( + table( + columns: (auto, auto, auto), + table.header([Parameter], [Value], [Notes]), + [Rail height], [$qty(6.35, "mm")$ ($qty(0.25, "inch")$)], [Matches cassette lip height], + + [Channel width], + [$qty(38.1, "mm")$ ($qty(1.5, "inch")$) $plus 0.2 "/" minus qty(0.0, "mm")$], + [Accepts cassette body with clearance], + + [Channel depth], [$qty(5, "mm")$ minimum], [Guides cassette during insertion], + + [Rail length], [Full chassis depth], [Front to rear], + ), + caption: [Chassis cassette rails geometry], +) + +==== Retention + +Cassettes must be retained to prevent accidental ejection during operation or +transport. + +#figure( + table( + columns: (auto, auto), + table.header([Method], [Requirement]), + [Friction fit], [Acceptable for stationary installations], + [Positive retention], [Required for portable or vibration-prone environments], + + [Front panel screws], [Optional, into chassis front rail], + ), + caption: [Chassis cassette retention requirements], +) + +Positive retention may be achieved via: +- Spring clips engaging cassette lips, +- Latching mechanisms. + +==== Material + +The rails must be of the same metal as the chassis, with a smooth, burr-free +finish; and bond to chassis earth. + +They contribute to EMI shielding by closing the gap between cassette lips and +chassis structure. + +=== Thermal management + +==== Cooling method + +Passive convection cooling is the baseline requirement. Forced-air cooling may +be added for high-density configurations. + +#figure( + table( + columns: (auto, auto), + table.header([Method], [Requirement]), + [Passive (convection)], [Minimum for all chassis], + [Active (forced air)], [Optional, for high-capacity or enclosed installations], + ), + caption: [Chassis cooling method requirements], +) + +==== Ventilation + +Chassis ventilation must align with cassette ventilation slots to enable +chimney-effect airflow. + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Bottom ventilation], [Required, aligned with cassette bottom vents], + [Top ventilation], [Required, aligned with cassette top vents], + [Slot dimensions], [$lt.eq qty(10, "mm") times qty(2, "mm")$ for EMI compliance], + + [Open area], [$gt.eq qty(20, "percent")$ of cassette footprint area], + ), + caption: [Chassis ventilation requirements], +) + +==== Thermal limits + +Inside the chassis cassette chamber, internal ambient temperature must not go +over $qty(50, "dC")$. If passive cooling cannot maintain thermal limits at full +capacity, forced-air cooling or reduced capacity is required. + +=== Power distribution board + +The power distribution board generates and distributes all power rails to +module positions. + +==== Functions + +#figure( + table( + columns: (auto, auto), + table.header([Function], [Requirement]), + [AC-DC conversion], + [Mains input to $plus.minus qty(15, "V")$, $plus.minus qty(5, "VD")$ rails. Can be external or internal], + + [Reference generation], [$plus.minus qty(10.0000, "V")$ precision references], + + [Master oscillator generation], [Generation of the $qty(10, "MHz")$ sine wave reference], + + [Distribution], + [ + - One female DB-25 connector per module position, + - One female isolated BNC connector per module position + ], + + [Calibration], [Front-panel accessible switches], + [Protection], [Overcurrent, overvoltage, thermal shutdown], + ), + caption: [Power distribution board functional requirements], +) + +==== Power entry + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Mains connector], [IEC C14 (with integrated fuse) or regional equivalent], + [Voltage range], + [$qtyrange(100, 240, "VAC"), 50 "/" qty(60, "Hz")$ (universal) recommended. Factory setup accepted], + + [Safety], [Compliant with IEC 60950-1 or IEC 62368-1], + ), + caption: [Power entry requirements], +) + +==== Master oscillator + +To support the metrologic tier time-domain computations, the chassis must +include a precision clock source. + +/ Oscillator: Oven Controlled Crystal Oscillator (OCXO). + / Recommended part: AOCJY4A-10.0000MHZ-SW (or equivalent with + $plus.minus qty(10, "ppb")$ stability). +/ Buffering: The oscillator output must be filtered to remove harmonics and + buffered to drive the $qty(50, "ohm")$ distribution network. + / Metrologic tier buffer: LM7171 (high speed, high voltage operational + amplifier) or equivalent, configured to drive $qty(50, "ohm")$ loads with + high slew rate and low distortion. +/ Signal level: $qty(1.0, "Vpp") plus.minus qty(10, "percent")$ into + $qty(50, "ohm")$. +/ Waveform: Sine wave. +/ Fan-out: The oscillator distribution network must ensure port-to-port + isolation $gt qty(40, "dB")$ to prevent oscillator line crosstalk between + modules. + +=== Front panel + +The chassis front panel provides system-level controls and reference inputs and +outputs. + +==== Elements + +#figure( + table( + columns: (auto, auto, auto), + table.header([Element], [Type], [Function]), + [SAME logo], [Label], [N/A], + [SAME license], [Label], [Legal], + [Power switch], [Rocker or toggle], [Mains on/off], + [Standby switch], [Toggle], [Maintains reference ovens temperature], + [Power indicator], [LED], [Indicates power state], + [Standby indicator], [LED], [Indicates standby state], + [$plus qty(10.0000, "V")$ output jack], [4mm banana, yellow], [Reference voltage output], + + [$qty(-10.0000, "V")$ output jack], [4mm banana, blue], [Reference voltage output], + + [$plus qty(10.0000, "V")$ input jack], [4mm banana, white], [Reference voltage input], + + [$qty(-10.0000, "V")$ input jack], [4mm banana, white], [Reference voltage input], + + [AGND jack], [4mm banana, black], [Analog ground reference], + [Dual $qty(10, "MHz")$ sine oscillator output jacks $plus.minus qty(1, "V")$], + [4mm banana, light blue], + [Master oscillator output (independent paths, to allow verification - see #ref())], + + [$qty(10, "MHz")$ sine oscillator input jack], [4mm banana, white], [Master oscillator input], + + [Calibration coarse], [Rotary or DIP switch], [Reference voltage coarse adjust], + + [Calibration fine], [Rotary or DIP switch], [Reference voltage fine adjust], + ), + caption: [Chassis front panel elements], +) + +- Case designers may add other elements as they see fit (fuse holders, voltage + selectors, sensors, etc.), +- Reference jacks should be grouped together, on a $qty(0.75, "inch")$ grid, +- All controls and jacks must have an associated label. + +=== Electrical safety + +==== Mains isolation + +#figure( + table( + columns: (auto, auto), + table.header([Parameter], [Requirement]), + [Isolation voltage], [$gt.eq qty(3000, "VAC")$ mains to SELV], + [Creepage / Clearance], [Per IEC 60950-1 or IEC 62368-1], + [Fusing], [Primary slide, appropriately rated], + [Earth bonding], [Continuous, $lt qty(0.1, "ohm")$ to mains earth], + ), + caption: [Mains isolation requirements], +) + +==== SELV circuits + +All module-facing voltages ($plus.minus qty(15, "V")$, $plus.minus qty(10, "V")$, $plus.minus qty(5, "V")$) are Safety Extra-Low Voltage (SELV): + +#figure( + table( + columns: 2, + table.header([Parameter], [Requirement]), + [Maximum voltage], [$lt qty(60, "VDC")$], + [Isolation from mains], [Required], + [User accessible], [Yes (banana jacks)], + ), + caption: [SELV circuits requirements], +) + +==== Protective earth + +#figure( + table( + columns: 2, + table.header([Parameter], [Requirement]), + [Earth continuity], [$lt qty(0.1, "ohm")$ from any exposed metal to mains earth], + + [Earth current capacity], [Per fuse rating], + [Chassis bonding], [All panels bond], + ), + caption: [Protective earth requirements], +) + +=== Compliance + +Chassis must comply with applicable safety and EMS standards for the target +market: + +#figure( + table( + columns: 3, + table.header([Region], [Safety], [EMC]), + [EU], [IEC 62368-1], [EN 55032, EN 55035], + [USA], [UL 62368-1], [FCC Part 15], + [International], [IEC 62368-1], [CISPR 32, CISPR 35], + ), + caption: [Chassis compliance requirements], +) + +Compliance testing and certification are the responsibility of the chassis +manufacturer. diff --git a/pictures/chassis-module-loading.svg b/pictures/chassis-module-loading.svg new file mode 100644 index 0000000..47e5449 --- /dev/null +++ b/pictures/chassis-module-loading.svg @@ -0,0 +1,895 @@ + + + + + + + + + + + + + + + + + + + + + SIDE ELEVATION CUTAWAY + Chassis Enclosure & Module Interface Clearance + + + + + + + + + + + + + + + + + + + + 177.8 mm (4U / 7.0") + + + + 6.35 mm + + + + 165.2 mm + + + + 152.5 mm + + + ≥ 25.0 mm + Cable bend & connector zone + + Chassis structure (steel 1.5mm / AL 2.0mm) + Continuous EMI shielded enclosure + + DB-25 backplane connector + (Cassette grounded via shell & pin 25) + + Cassette guide rails (earth bonded) + + + + FRONT ELEVATION + Module Pitch & Slot Interface Alignment + + + + + + + + + Module 1 + + + + + + + + + Module 2 + + + + + + + Empty slot + (Rails visible) + + + + 38.1 mm (1.5") + + + + 38.1 mm pitch + + + + 177.8 mm + + + + + CASSETTE RAIL GEOMETRY & RETENTION + Cross-Section of Rail Guide Channel (Scale Enlarged) + + + + + + + + + + + + + 38.1 mm +0.2/-0.0 (channel width) + + + + 6.35 mm (0.25") + (rail height) + + + + ≥ 5.0 mm (depth) + + Optional positive retention + (Spring clip /latch mechanism) + + Cassette lip insertion clearance + Metal-to-metal grounding contact + + + + + + + + + + + + + + + + + + + + diff --git a/preamble.typ b/preamble.typ index 2b89590..8e1911d 100644 --- a/preamble.typ +++ b/preamble.typ @@ -13,6 +13,8 @@ #add-unit("rack unit", "U", "upright(U)", space: false) #add-unit("ounce", "oz", "upright(\"oz\")") #add-unit("american wire gauge", "AWG", "upright(\"AWG\")") +#add-unit("volt AC", "VAC", "upright(V_\"AC\")") +#add-unit("volt DC", "VDC", "upright(V_\"DC\")") #set document( title: [SAME Analog Modular Ecosystem], @@ -104,8 +106,14 @@ drawings) are licensed under CERN-OHL-S-2.0+. = Compliance verification +== Foundational invariants + +=== The time invariant + = Reference implementation +== Chassis + = Theory of operation = Applications -- cgit