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MODEL 250
FEATURES

Precision 50 kV DC divider HV probe

  • Excellent accuracy: 0.05% from 0 to 50 kV
  • 1,000 MΩ input impedance
  • Temperature coefficient under 50 ppm/°C
  • Compact: only 12 inches in length
  • Compatible with all CPS probe tips
  • Measures DC voltages only
DESCRIPTION

Model 250 is a precision, high voltage resistive divider probe that allows low-level voltmeters to safely and accurately measure DC voltages (only) up to 50 kV. Its unusually short length — only twelve inches — is made possible by our oil-free, state-of-the-art epoxy encapsulation technology. Divider ratios of 1000:1 and 10000:1 are standard, and calibration is traceable to NIST primary standards. Its excellent accuracy, high load impedance, and compact size make it ideally suited for calibrating, monitoring and testing a wide range of high voltage equipment, including HV power supplies, CRT display systems, microwave systems, and nuclear instrumentation. For higher voltage applications, the Model 500 100 kV probe is also available.

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. 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 also available to meet a range of application requirements. The probe 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

CHOOSING A PROBE

Four standard versions of the model 250 probe are available (see table below). Each model is calibrated to work with voltmeters having a specific input impedance characteristic, and will produce an output voltage that is scaled by either 1000:1 (1 V out per kV) or 10000:1 (100 mV out per kV).

Probe PN Voltage Divider Ratio Meter Impedance
250-M-01 1000:1 10 MΩ
250-M-001 1000:1 1 MΩ
250-G-01 1000:1 > 10 GΩ *
250-G-10 10000:1 > 10 GΩ *
* Sometimes denoted "open cal"

Calibration

Every probe is factory calibrated to compensate the input impedance of the voltmeter or other measurement instrument it will be connected to. Consequently, you must know your meter's impedance so you can select a probe that has the proper compensation.

Handheld meters commonly have 10 MΩ input impedance, whereas high quality bench meters typically have impedances exceeding 10 GΩ. Note that some meters have a different input impedance for each input range, so be sure to base your probe choice on the meter range that will be used. Use models 250-M-xx with meters that have 10 MΩ input impedance, or models 250-G-xx with meters that have > 10 GΩ impedance (denoted as "open" in probe description). Custom calibrations are also available; please contact us if you need to compensate a non-standard meter impedance.

No AC calibration is performed. This probe is not recommended for AC measurement.

Divider ratio

The choice of voltage divider ratio depends primarily on your voltmeter's measurement resolution and input impedance. In the case of high resolution meters, a ratio of 10000:1 is recommended because the meter can measure the probe's full 5 V output without changing range (and therefore input impedance). Lower quality meters may have low resolution and thus require the higher output provided by a 1000:1 probe.

Alternatives in digital probes

CPS also offers model 255, a digital 50 kV probe. Instead of connecting to a voltmeter via BNC, this digital probe can communicate directly with a computer or tablet via USB. We recommend using model 255 in cases where a computer is available and a standalone voltmeter is not required. Model 255 takes the guesswork out of probe selection, and it can often eliminate the need for an expensive, high-accuracy meter.

ACCESSORIES

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 divider 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 kV) and its load. It also provides a surge-protected, AC-coupled output jack that can be connected to an oscilloscope or AC voltmeter for ripple measurement.
SPECIFICATIONS
Input
Input voltage-50 to +50 kVDC
Input impedance1,000 MΩ
Output
Divider ratios1000:1 (50 kV ⟼ 50 V out) — models 250-X-01
10000:1 (50 kV ⟼ 5 V out) — models 250-X-10
Accuracy< 0.05% error *
Temperature coefficient< 50 ppm/°C
Output connectorBNC
Mechanical
Weight1.8 lb
DimensionsView mechanical drawing

* Standard probes are factory calibrated to minimize errors from 10 to 50 kV and then tested to ensure accuracy across the probe's operating range. We can calibrate across a different, custom range upon request, but cannot guarantee specified accuracy across the probe's operating range in such cases. Custom calibration ranges must be specified when ordering.

DOWNLOADS
Product manualModel 250 Instruction Manual
PRICES
Model Description Price Order Qty.
1 2–9
HV Probes
250-G-01 50 kV probe, open cal, 1000:1 $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
250-G-10 50 kV probe, open cal, 10000:1 $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
250-M-01 50 kV probe, 10 MΩ cal, 1000:1 $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
250-M-10 50 kV probe, 10 MΩ, 10000:1 $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
HV Probes (Legacy part numbers)
0250-00-0001 50 kV probe, open cal, 1000:1 (HVP-250) $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
0250-00-0005 50 kV probe, open cal, 10000:1 (HVP-250) $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
0250-00-0012 50 kV probe, 10 MΩ, 1000:1 (HVP-250) $480 $436
Includes one, 250B, corona ball tip per order $0
Includes one, 250P, pointed tip per order $0
Includes one, 250S, connector insert per order $0
Includes one, 250CBL, 36-inch multimeter cable per order $0
Probe Tips
250B HV probe tip, corona ball $47 $47
250P HV probe tip, pointed $18 $18
250H HV probe tip, hook $14 $14
250S HV probe tip connector insert $2 $2
Probe Cases
252CASE Storage case for 50 kV probes $175 $175
Viewing Blocks
HVT30 30 kV viewing block with AC-coupled out $600 $600
Cables
250CBL 36-inch multimeter cable for CPS high voltage probes $24 $24