Hi folks,
As promised, here is Ellman's response, drafted by Dr. Frank Lin PhD Director of Engineering.
...This statement is specifically to address the neutral Electrode Monitoring Circuit (NMC) of the Ellman Surgitron 120 IEC Electrosurgical Generator.
The NMC implements an isolation transformer to provide the necessary isolation from patient circuits to meet IEC60601-2-2 safety requirements.
It has a frequency of ~1.3LHz with 5Vpp output voltage between the split neutral plates.
It is an AC low frequency voltage to meet the 12V limitation by IEC60601-2-2 standard 59.10 / monitoring curcuits. The current limitation of the monitoring circuit of the split neutral electrode is specified in 19.3.
As a low frequency leakage current, Table IV of IEC60601-1 applies and the limitation is 100uA....
He goes on to explain the rigorous testing to current standards at two independent test houses, BSI and UL.
From his explanation it would seem that my safety tester, Biotek 601pro, is the culprit.
During leakage tests it performs as follows...
Normal polarity - no fault condition,
it uses the DC limit - and fails.
Reverse polarity - no fault condition,
it uses the AC limit - and passes.
Normal polarity - single fault condition,
it uses the AC limit - and passes.
I will of course be talking to Ultramedic about this problem.
A copy of this explanation letter was sent to the MHRA by Ellman.
Thanks for all the contributions.
Pete