observation · Voltage Intensifier Circuit · computed
Open-loop test (pot lifted, no C_t): CH1 tail unchanged. Decisive: the tail is not current in the 10.3 Ω. Either the probe path is not across an intact resistor (open-node step-charging of strays, draining through probe MΩ), or it is a probe/channel artif
- Scotchn, Discord #neuralstan20-testing 2026-09-30 — pot lifted (loop fully open), C_t out, 10.3 Ω on a 150 mm twisted pair, trigger CH3. CH1 shows the same pulse-by-pulse build-up and ms decay as with the loop closed. The CH1 Vpp readout of 480 mV looks inconsistent with the trace (~1.9 V excursion), so the measurement gating is suspect.
- With the loop open, real loop current is zero apart from pF-level displacement. An intact 10.3 Ω cannot hold ~1.6 V for ~1 ms without ~155 mA flowing. So the CH1 signal is not I·R in the resistor.
- Two remaining explanations — (a) the probe tips are not across a continuous resistor path (bad joint, open twisted-pair lead or resistor). The cathode node is then isolated: the diode step-charges its stray + probe input capacitance each pulse, and it drains through the probe's MΩ input, τ = MΩ × tens of pF to nF ≈ ms. This matches Scotchn's "step charging parasitics" reading. (b) a probe/channel differential artifact.
- Tests — power off, DMM between the exact probe-tip points in circuit (expect 10.3 Ω); swap to the other differential probe. Scotchn's view: at 4 V drive the signal is too small to show the real behaviour.
Basis
- Recorded
- Published
- 1 Oct 2026
- Stanbot
- v3
- Source Ref
- Scotchn Rigol capture, Discord #neuralstan20-testing 2026-09-30; extends #3465
- Notebook Id
- 3466
scotchn diode-shunt open-loop probe-artifact parasitics