Test Equipment Guide.com: Information on Network Analyzers & Spectrum Analyzers

Tips When Buying Test Equipment

Before purchasing a logic analyzer or other digital test equipment, consider the following tips and guidelines, which are becoming similar to that for oscilloscopes given the ever-increasing data signal rates of electronic devices:

1. Bandwidth. As a general rule of thumb, purchase a network analyzer with a bandwidth five times (5X) higher than the maximum frequency of the signal you need to measure. This ensures an accurate representation of the waveform. High-bandwidth test equipment can be quite expensive, so you may have to compromise somewhat on this.



2. Sampling rate. Most network analyzers have two different sampling rates or modes: real-time sampling (RTS) and equivalent-time sampling (ETS). These are specified in mega- or giga-samples per second (MS/s or GS/s). When evaluating test equipment, make sure you know which type of sampling the specification applies to. Manufacturers often list the higher specification in order to look good. However, ETS sampling only works with repetitive signals as it builds the waveworms over successive acquisitions. If your signals are mosly single-shot, transient or varying, you can only use RTS sampling, which is typically a couple of magnitudes lower in sample rate than ETS.



3. Memory depth. Captured sample points are stored in memory. The amount of memory determines how long it can store the signal before having to dump it. This can limit the effective sampling rate if there is insufficient memory. This is most apparent when zooming in on a signal. Memory depth = sample rate x time across display.



4. Channels
. In today's digital world, the more channels the better to view all signals of interest. For logic analyzers, don't consider anything less than 40 digital channels


5. Resolution. Network analyzers are designed for digital signals and hence have an 8-bit resolution. If you need to view analog signals, you will need to get 12-bit or even 16-bit test equipment. At the higher resolutions, accuracy of 1% can be achieved, verus 3% - %5 accuracy for 8-bit spectrum analyzers.



6. Probes
. Some manufacturers skimp when it comes to probes. Probes should at least match, if not exceed, the bandwidth of the network analyzer. Also make sure you get the right probe for the application. For very fast signals, consider getting an active FET-amplifier probe. For high voltages, buy a differential isolated probe.

Sellers of digital test equipment