Model 255 is a USB 2.0 compatible high voltage probe that measures DC voltage up to 50 kV with very high accuracy. Unlike conventional analog probes, it requires no meter-dependent compensation or divider ratio. Model 255 does not measure AC voltage.

It employs a high resolution digitizer and embedded processor that work together to greatly reduce sensitivity to voltage coefficients and temperature variations, thus largely eliminating the primary sources of error found in purely analog probes. For higher voltage applications, the model 505 100 kV USB probe is also available.

The probe's unusually short length is made possible by our oil-free, state-of-the-art epoxy encapsulation technology. DC calibration data is traceable to NIST primary standards. Its outstanding accuracy and compact size make it ideal for calibrating, monitoring and testing a wide range of high voltage equipment, including power supplies, CRT display systems, microwave systems, and nuclear instrumentation.

Digital interface

The probe's built-in data acquisition system is entirely USB powered. It simultaneously measures high voltage DC, high voltage RMS AC, and internal temperature, and detects peaks in high voltage DC. The resulting digital values are sent over USB to a user supplied host computer for display, recording, or analysis, as required by the application.

If desired, two or more probes can be connected to different USB ports on a single computer and used at the same time. Free demo programs are available for user supplied Windows and Android hosts, and an API is provided for custom application development.

Safety

The probe includes an attached grounding cable which, when connected to a suitable ground potential, protects the operator and measurement system from high voltage exposure. An audible warning sounds and a visual indicator lights if the probe tip is brought near high voltage while the protective ground is unconnected.

A high voltage bell is integrated into the probe body between its handle and high voltage tip to increase the surface path length, effectively increasing the distance between operator and high voltage.

Probe tips

A variety of interchangeable probe tips are available to meet a range of application requirements. The probe's high voltage end has a threaded opening that allows standard CPS tips as well as custom tips to be easily attached. Two additional threaded openings are provided in the high voltage bell to allow the probe to be securely mounted to a measurement system.

Included Accessories

• 1-corona ball tip
• 1-pointed tip
• 1-connector insert
• 1-USB cable

Probe Tips

Three standard, interchangeable tips are available:

PN	Image	Description
250B		Corona ball tip. This probe tip has a large radius of curvature that helps to minimize arcing to the tip when making and breaking high voltage connections. The contact end has an opening that serves as a jack for standard banana plugs. A connector insert (PN 250S) is required to attach this tip to the probe.
250P		Pointed tip for probing circuitry in confined spaces where a corona ball won't fit. The contact point has a moderate radius of curvature to reduce arcing, and extended length to allow selective probing. A connector insert (PN 250S) is required to attach this tip to the probe.
250H		Hook tip. This tip allows the probe to hang on a suitably shaped high voltage electrode for hands-free operation. It screws directly into the probe and does not require a connector insert.
250S		Connector insert. A connector insert is required to attach the probe to a 250B or 250P probe tip. One end screws into the probe and the other into the probe tip. A single insert can be shared by multiple tips, though it's handy to have two if the tips are changed frequently.

Protective Case

The probe is a precision instrument that should be protected when not in use. An optional instrument case is available for this purpose:

PN	Image	Description
252CASE		Instrument case. This sturdy case will accommodate a probe, a complete set of probe tips, connector inserts, and instruction manual. It securely holds the probe and accessories in a shock absorbing, custom fitted molding. The hinged handle allows for easy handling and compact storage.

Viewing Block

For applications up to 30 kV, this viewing block provides a convenient way to make a three-way connection between probe, power supply and load:

PN	Image	Description
HVT30		Viewing Block. This unit provides a convenient and safe way to connect your probe to a HV power supply (up to 30 kVDC) and load. It also provides a surge-protected, AC-coupled output jack that can be connected to an oscilloscope or AC voltmeter for ripple measurement.