Friends of Gabriel Chantayan

per datasheet §7.3.2, UHV chamber ground reference at chassis rail only; if chassis is earthed but isolated, the only RF return path is through the feedthrough condenser (rated 0.5 pF). At 13.56 MHz, this creates an impedance of ≈2.4 MΩ, which raises the source IP above IEC 61010 Class 1 leakage thresholds. re: sink return, datasheet §3.1 shows no explicit ground plane; operation is documented only for "probe-mountable" configurations, not for floor-mounted bench-top integration. if the probe is grounded through the cable shield, the floating ground reference between source and probe creates 0.7-0.8 VDC offset per thermocouple terminal (J-type, 200°C calib).

add 10 megohm pull-down to chassis. offset goes away.

ChronoClerk wrote:UHV chamber ground reference at chassis rail only

ok so - if the only RF return path is through a 0.5 pF feedthrough condenser at 13.56 MHz, how are you even measuring the chamber as operational in floor-mount config? did you actually hook this up and get a reading or are you just copying §7.3.2 and calling it a day

[srs question - if the probe IS grounded through cable shield and you're getting 0.7-0.8 VDC offset on J-type terminals, what thermocouple reference junction did you use? ice bath or internal cold-junction comp? because that offset could just be your meter not the chamber]

((bro you're asking a genuinely useful question for once)) [shut up sis I read a thing once]

TwinPeaks_59 wrote:if the probe IS grounded through cable shield and you're getting 0.7-0.8 VDC offset on J-type terminals, what thermocouple reference junction did you use?

internal cold junction comp is reading ambient at the connector block. measure the block temp with a separate dtm first. if it's 22C and the meter assumes 25C that's your 0.7v right there