When Picotest M3500-OPT01( 10 inputs) scanning card inputs are connected to mains isolated 230 VAC 50 Hz, it sometimes does not measure - there is zero (or very low value) instead around 230 VAC. This does not happen at 120 VAC.
It seems relays inside are not making contact or are not even driven. In some cases, one relay seem to be left in ON state while next channel is enabled. This leads to contact welding which is understandable.
I am aware 230 VAC is beyond card official rating (125 VAC 100 kHz CAT II), yet within relay specs (NEC or NEXEM EA2-5TNJ depending on unit) which is rated for 250 VAC switching voltage, 1000 VDC, 1500 V surge. This is two coils latching type.
I would expect contact wear, too high crosstalk, even arc-over but incorrect operation of relay control.
While system will use different DMM, I would like to understand what root-cause may be. Any ideas?
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