Tags/Project: Equipment-wiki
| Metadata Field | Document Information |
|---|---|
| Status | Under Review |
| Created | 2026-09-18 |
| Last Updated | 2026-09-29 |
| Author | Davide Cuneo |
| Rev. # | 1.4 |
| Reviewers | Davide |
Note
This document reconstructs, in written form, the explanation given verbally by Kevin about the patch panel wiring logic connecting the PotAim chassis to the HF/LF DAQ. Some details (flagged at the end) may need a final confirmation from Kevin before this is marked as reviewed.
Introduction and Context
This document describes the signal routing logic implemented on the patch panel that brings the analog outputs of the PotAim chassis into the DAQ system, for both the HF (high frequency) and LF (low frequency) acquisition. Even though the HF acquisition system is expected to be the one used most often during monitoring, the LF system is also actively used: for instance, when the current is ramped up, held stable for around 4 minutes, and then ramped down, the LF acquisition needs to be watched during the stable phase, otherwise its memory can fill up before the ramp-down is even reached.
PotAim Signal Overview
Each PotAim chassis hosts 10 PotAim cards, each providing 2 analog outputs, for a total of 20 output signals per chassis. Across the two chassis currently available, this adds up to a maximum of 40 individual voltage signals. These signals leave the PotAim chassis on a single cable terminated with a large Burndy connector, nominally rated for 48 pins, although not all of them are actually used. This cable runs from the PotAim chassis to the back of the patch panel.
Analog Inputs (AI) – Back of the Patch Panel
On the back of the patch panel, several groups of inputs can be accessed, each through its own 28-pin Burndy connector. Kevin uses the positions labelled AI 1 to 20, AI 41 to 60, and AI 61 to 80; the range AI 21 to 40 (position 2) is currently left unused, reserved for a possible future expansion that, in practice, is unlikely to be needed.
The two PotAim chassis are wired as follows: chassis n.1, which provides 20 signals, is connected to Burndy connector position 3 (AI3, pins 41 to 60); chassis n.2, also providing 20 signals, is connected to Burndy connector position 4 (AI4, pins 61 to 80). Position 1 (AI1, pins 1 to 20) is not used for the PotAim signals at all: it follows a completely different logic, described further down.
Analog Outputs (AO) – Back of the Patch Panel
Once inside the patch panel, the signals are sent onward to the various instrumentation through 10 flat cables carrying analog outputs, also located on the back of the panel. Each flat cable carries 8 signals, so you will see them labelled AO 0-7, AO 8-15, AO 16-23, and so on up to the tenth cable. Out of the 10 possible positions, Kevin has only wired 6 flat cables, giving a maximum of 6 × 8 = 48 signals that can be sent out to the instrumentation. This is, in fact, the total number of signals sent to the DAQ from the HF patch panel.
Of these 48 available output signals, 40 are filled by the two PotAim chassis. The wiring is done so that the connection between AI and AO is strictly one-to-one: the flat cables carrying these 40 signals occupy positions 6 to 10 (5 flat cables in total), matching exactly the 40 pins coming in on AI3 and AI4. As an example of this correspondence, pin 20 of AI4 (which Kevin thinks of as “the 80th pin” overall) corresponds to pin 80 on the output side, i.e. the 8th pin of the flat cable in position 10.
Because of this one-to-one mapping, no connection is visible on the front of the panel between the IN and OUT sockets for the PotAim-related pins: Kevin shortened them internally, actually welding the connectors together. This internal welding was done only for the IN/OUT pairs related to the PotAim signals, which is exactly why the last 5 output flat cables (positions 6 to 10) are the ones dedicated to them. Following this logic, for PotAim chassis 1, card 1, channel A, the signal starts from pin 40 — corresponding to pin 1 of Burndy connector position 4, on the IN side — and the rest of the signals can be mapped in the same straightforward way (see the flagged point below on this specific pin number).
Known Issue: Flat Cable Connections
One recurring problem with this setup concerns the flat cables: since they cannot be screwed into place, they often fail to make full contact, and disconnections happen quite frequently. This is worth keeping in mind whenever a signal appears missing or noisy: before suspecting an instrument or a PotAim card, it is worth checking whether one of the flat cable connectors has simply worked loose.
AI1 – Trigger and DCCT Signals (Front Panel)
AI1 follows a different logic altogether. Pin 1 of AI1 carries the Trigger signal coming from the Safety Matrix, which is what makes the DAQ start recording data whenever a quench, or another trigger event, occurs. For this group of pins, the IN and OUT sockets on the front of the patch panel are connected using LEMO cables rather than being welded internally. Kevin has shortened most of these IN/OUT pairs directly, with the exception of the DCCT readings (one pair per couple of power converters) which are found on IN 7 and IN 8. The remaining inputs in this group are currently not in use, but they are available if, in the future, there is a need to bring in additional external signals.
Front Panel Connection Logic
As a general rule, the connections between IN and OUT on the front of the patch panel are one-to-one: for example, IN 77 is connected to OUT 77. For the PotAim-related pins (AI3 and AI4) this 1:1 connection is realised internally, by welding, so it is not visible from the front of the panel; for the AI1 pins, the same 1:1 logic is instead implemented visibly, through LEMO jumper cables.
The LF System and Current Limitations
The LF system follows the same overall logic as the HF one, but it is not meant to be touched: Tommaso, who used to operate it, never modified anything on the LF side. At present, the setup has no spare capacity for a third PotAim chassis — adding one would mean redoing all the connections from scratch, since AI1 is already dedicated to trigger/DCCT signals, AI3 and AI4 are fully occupied by the two existing chassis, and AI2 (pins 21 to 40) is only a reserve that is not expected to actually be used.
Overall, the system currently carries a maximum of 40 pins to the patch panel from the PotAim side, which corresponds to a maximum of 20 differential signals, since each one is read as a positive/negative pair.
Quick Reference – AI Back-Panel Mapping
| Back-panel position (Burndy connector) | Pin range | Assigned to |
|---|---|---|
| AI1 | 1–20 | Trigger (pin 1, from the Safety Matrix), DCCT readings (IN 7 & IN 8), remaining pins unused/spare — routed via LEMO cables on the front |
| AI2 | 21–40 | Unused, reserved for possible future expansion (unlikely to be needed) |
| AI3 | 41–60 | PotAim chassis n.1 — 20 signals |
| AI4 | 61–80 | PotAim chassis n.2 — 20 signals |
For the Safety Matrix:
Energy Extraction works with a different logic. He says not to pull the cards out. Usually you don’t have to replace them but if you have we have to be careful.
Feedback
Found an error or something outdated in this note? Please contact Davide Cuneo (davide.cuneo@physics.uu.se).