Cable Tests

Introduction 4

The symptoms of a split pair range from non-existent to a complete lack of communication. In some cases a split pair cable may work just fine for 10BASE-T but not at all for 100BASE-TX.

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Figure 4-5. Split Pair

A split pair cannot be identified with a conventional wiremap test because it is the wire pairing that is incorrect rather than the physical connection. Another technique must be used.

The most common method of identifying a split pair is by measuring the Near End Crosstalk (NEXT). This is a very reliable method but, unfortunately, it requires the use of a remote unit at the far end. The Network Assistant uses another equally reliable method that does not require a remote unit at the far end (except in the case of short cable lengths). The Network Assistant identifies split pairs by measuring the characteristic impedance of each wire

pair. A split pair’s characteristic impedance is much greater than the impedance of correctly paired wires.

Cable Length

The 10BASE-T and 100BASE-TX cabling specifications limit the maximum device-to-device cable length to 100 meters. There are many ways to measure a cable length; the Network Assistant uses a very accurate method called Time Domain Reflectometry (TDR).

The TDR method works much like a radar system that emits a pulse of electrical energy and then interprets the reflected electrical energy. To measure the length of a cable using the TDR method, a pulse of electrical energy is sent down a wire pair, the reflected electrical energy is interpreted to get the time delay between the transmitted and reflected pulse, and the length of the cable is computed using the cable’s Nominal Velocity of Propagation (NVP).

The NVP is a value for how fast a pulse travels down a given cable. Cable manufacturers specify how fast electricity travels down a cable as a percentage of the speed of light (186,000 miles/second or 300,000,000 meters/second). A cable with an NVP of 72, for example, means that electricity travels at 72% of the speed of light along the cable.

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Fluke Series II user manual Cable Length, Split Pair
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Series II specifications

The Fluke Series II is a cutting-edge line of industrial multimeters that incorporates advanced technology and features tailored for professionals working in critical environments. Renowned for their precision and reliability, these multimeters are quintessential tools for technicians and engineers alike, whether in manufacturing, electrical engineering, or maintenance applications.

One of the hallmark characteristics of the Fluke Series II is its robust design. Constructed to endure harsh working conditions, these meters come equipped with a high-impact casing that protects against drops and vibrations. Their IP67 rating ensures they are dust-tight and can withstand temporary immersion in water, making them ideal for fieldwork in tough environments.

The Series II boasts a range of measurement capabilities. With the ability to measure voltage, current, and resistance, as well as additional readings such as frequency, capacitance, and temperature, these multimeters deliver unparalleled versatility. Many models in the Series II also feature True RMS (Root Mean Square) measurement capabilities, enabling accurate readings of non-linear and distorted waveforms, which are increasingly common in modern electronics.

Another significant feature is the advanced display technology. The Series II multimeters often come with large, high-contrast LCDs that facilitate easy reading in various lighting conditions. Some models even offer graphical displays, enabling users to visualize trends in measurement data over time.

User-friendliness is also a hallmark of the Fluke Series II. With intuitive interfaces and simplified navigation, users can access advanced features quickly. Auto-ranging capabilities allow the meter to automatically select the appropriate range for the measurement, minimizing user errors and streamlining the testing process.

Fluke's commitment to safety is underscored by the design of the Series II, which includes features such as safety-rated test leads, protective rubber booting, and a high-voltage warning indicator for added peace of mind.

Moreover, the connectivity options within the Series II enable seamless data transfer to PCs and mobile devices, facilitating easier logging and analysis of measurement data. Many models support Bluetooth or USB connectivity, making it easier than ever to integrate multimeter readings into existing data collection and analysis workflows.

In conclusion, the Fluke Series II multimeters stand out for their durability, versatility, and user-centric features. Their combination of advanced measurement technology, rugged design, and safety functions makes them essential instruments for professionals who demand accuracy and reliability in their work. The commitment to innovation and excellence that Fluke exemplifies ensures that the Series II remains a trusted choice in the field of industrial measurement tools.
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