Measurements (and the test instruments to perform them) must evolve to keep pace with emerging technologies. The past few years have already yielded major electronic technology advances, such as Fifth Generation (5G) cellular networks at millimeter-wave frequencies and radar-guided autonomous vehicles. It is a new year with more to come. The start of a new year is often a good time to review current and future test needs and decide if it might also be time to upgrade some of that “good old test gear.”
Upgrading test equipment should never be a quick decision or spontaneous reaction. It should be carefully considered, in the mindset of testing requirements for years to come. Those requirements are usually based on technology trends, such as increasing data rates, frequencies, bandwidths, and even dynamic ranges. Even when frequencies do not increase, the types of signal to be tested may change, according to modulation requirements. Or it may be high-speed pulses which must be tested instead of CW signals. Applications for wireless signals have grown steadily for more than 30 years, with no signs of letting up. Frequencies continue to grow and test equipment must keep pace to thoroughly test today’s and tomorrow’s wireless devices and systems.
Test instrument upgrades provide opportunities for improvement: to make up for what is missing in an instrument or test setup, be it measurement speed, accuracy, bandwidth, sensitivity, resolution, even more measurement channels. A scope with four channels may provide much more flexibility for testing than a two-channel model. The latest batch of oscilloscopes from Tektronix now offer up to eight channels in models such as MSO58 and MSO68B. For companies that contract outside measurement services because they lack the capability to perform the tests in-house, instrument upgrades offer the chance to bring those measurements in-house.
Sometimes an instrument upgrade is necessary simply because a trusted instrument has become obsolete. Its manufacturer may no longer offer the instrument or technical support and calibration services for it, leaving its users vulnerable should it fail. Whether it is an oscilloscope, spectrum analyzer, or signal generator, the failure of one key component, such as a YIG oscillator in an RF/microwave swept signal generator, can result in the loss of the instrument. It may be possible to repair a damaged, obsolete instrument by finding replacements for the original components, (and Axiom can help you with that). But the repair and calibration costs required to bring the instrument back to specified performance levels may not warrant such action. An instrument upgrade may be a more economical solution, with the opportunity to meet or even exceed the performance levels of the instrument it is replacing.
Ideally, an instrument upgrade can be performed without disturbing effectiveness of an ATE setup. For automated measurement applications, an upgrade candidate should be software compatible with the other instruments in a test system. It should provide the control languages (such as SCPI) and electronic interfaces (such as GPIB) for seamless connection to a current test system or setup. Test instrument upgrades should be considered on a regular basis to avoid any engineer or company from the vulnerable position of being without vital measurement tools. Each new year is an easy reminder to look at a company’s or user’s current rack of test gear and whether the instruments “measure up” to current test applications.
The Keithley 580 micro-ohmmeter is an example of a workhorse instrument that has been on many test benches but is now obsolete. The micro-ohmmeter was designed for high-resolution measurements of low values of resistance. It was available with optional battery power to simplify its placement on a test bench (although something of an inconvenience when the battery charge ran low). Keithley offers several upgrade instruments for the model 580, including the 6.5-digit model 2750, the 7.5-digit model 2001, and the 8.5-digit model 2002; with various levels of micro-ohm resolution and accuracy to meet different testing requirements. These and other of the company’s micro-ohmmeters are available in half-rack and full-rack housings and full-scale measurement ranges from 1 to 20 Ω but without battery options. Keithley also provides a model 580 upgrade to be a dramatic improvement in measurement capability, by replacing it with the software-driven, automated model 6220 or 6221 current sources and model 2182A nanovoltmeter combination. The instrument pair can perform milliohm measurements with 10-nΩ resolution.
For microwave testing, the model 83650B signal generator from Agilent Technologies has been a trusted source of high-frequency test signals since the company changed its name from Hewlett-Packard Co. Agilent Technologies is now Keysight Technologies and the model 83650B is now obsolete, leaving those in need of test signals through 50 GHz and higher to find an alternative source. As an upgrade, Keysight offers its model E8257D PSG synthesized signal generator with a variety of frequency-range options, the widest of which is 250 kHz to 67 GHz. The 1-kHz standard frequency resolution of the obsolete model 83650B has been replaced by the stunning 0.001-Hz CW frequency resolution in the Keysight E8257D.
For vector signal analysis at such high microwave frequencies, the Lightning model 37397C vector network analyzer (VNA) from Anritsu Co. (which in its time replaced many older and now obsolete model 360 VNAs from Wiltron Co.) features a frequency range of 40 MHz to 65 GHz. VNAs are complex, multiple-receiver instruments designed for scattering-parameter (S-parameters) measurements at microwave frequencies. They require regular calibration and maintenance to maintain accuracy. For those seeking an upgrade for an older model 37397C VNA, Anritsu also offers its model MS4647A VectorStar VNA with frequency range of 10 MHz to 70 GHz well suited for measurements on millimeter-wave components for emerging 66-GHz automotive radar systems. With cleaner front panel and performance exceeding that of the model 37397C VNA, the model MS4647A VectorStar VNA is a similar-sized rack-mount instrument and designed for software compatibility when serving as an upgrade for older model 37397C VNAs in test systems.
These are just a few examples of possible upgrades. Users with large equipment racks may want more than a few upgrades, but realistic upgrades should be made over time and within budget. Many upgrade candidates can be found on the Axiom Test Equipment website at www.axiomtest.com, by contacting Axiom Test Equipment’s sales department at firstname.lastname@example.org, or by calling an Axiom sales representative at 760-806-6600 for advice on the best upgrade strategy for a particular instrument. And from all of us at Axiom, please have a safe, happy, and COVID-19-free 2021.