The High-Voltage Interface (HVI) is a safety instrument that transfers signals between a High-Voltage Amplifier (HVA) and a Precision tester when making measurements at voltages above the internal capabilities of the tester and up to ±10,000 Volts. The HVI routes the tester's low-voltage model of the intended signal to the HVA where it is amplified and returned, through the HVI HV DRIVE port to one sample electrode. The sample's charge response is collected from the opposite electrode at the HVI HV RETURN port and passed to the Precision tester. The HVI also passes a low-voltage model of the high-voltage signal out of the HVA from the HVA to the tester to be used to represent the actual voltage being applied.
Logic signals are passed between the HVI and the Precision tester through an I2C interface. The logic signals indicate the presence of the High-Voltage Interface to the tester and Vision software. They also provide the tester with HVA-specific information such as voltage output-to-voltage input ratio (amplifier gain factor), ramp rate (Volts/sec.), high-voltage output-to-low-voltage monitor scale factor, etc. Previous versions of the HVI required a separate HVA ID Module to represent the amplifier logic. Changing to an amplifier with different specifications would require a new ID Module. The current version of the HVI maintains the amplifier characteristics internally in an EEPROM. No ID Module is required. A new amplifier can be selected in software provided its characteristics have been specified to Radiant Technologies, Inc. and it has been incorporated into the C:\RT_USB\AccessorEEProm.txt file.
The primary purpose of the HVI is to detect voltages above 0.0 V at the HV RETURN port. This would represent an event that has caused the HV DRIVE voltage signal to short through and/or around the sample. In this case the voltage output into the amplifier is immediately terminated, protecting both equipment and the equipment operators. All high-voltage signals, along with the (normally) 0.0-Volt HV RETURN signal, are through 40,000-Volt monoaxial cables with rubber shielding sleeves.
High-Voltage Interface (HVI) Appearance
Figure 1 - HVI Front and Rear Panels.
Safety Features of The High Voltage Interface
Test path fully insulated with 50kV insulation to protect the end user.
High speed protection during breakdowns (less than a microsecond).
High voltage amplifier disconnected by HVI on dead shorts.
Safety Interlock on rear panel of HVI prevents high voltage application if not closed.
Unique amplifier identification procedure by the host computer prevents unassigned high voltage excursions.
