Precision 50 kV DC divider HV probe
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.
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.
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.
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).
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.
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.
Three standard, interchangeable tips are available:
The divider probe is a precision instrument that should be protected when not in use. An optional instrument case is available for this purpose:
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:
* 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.
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