In part 1 of this series, we looked at the strain gauge, which can be used to quantify how a test specimen deforms as a function of applied stress. We developed a Wheatstone-bridge circuit that makes use of strain-gauge elements in two of the bridge’s legs, as shown in Figure 1, a version of Figure […]
FAQ
Defining and measuring strain: part 1
A metallic foil strain gauge can detect how a test specimen responds when subjected to axial stress. In a previous series, we investigated the Wheatstone-bridge circuit topology and described how strain-gauge elements could be used in the bridge legs. Q: At that point, I asked the question, what is strain, and what are its units? […]
Making sense of test circuits with Kirchhoff’s laws: part 4
We can use a Wheatstone bridge voltage measurement to determine an unknown resistance value. In part 3 of this series, we used Kirchhoff’s voltage law to derive the branch currents and node voltages for an unbalanced Wheatstone bridge with five known, fixed resistors (Figure 1). Now, we propose to replace R5 with a digital multimeter […]
Noise generator substitutes for tracking generator
When your spectrum analyzer lacks a tracking generator, you can use a low-cost noise generator to characterize RF components. Here’s how. Low-cost spectrum analyzers often lack tracking generators, preventing you from having a signal source that tracks the analyzer’s frequency sweep. Not having a tracking generator can make some measurements difficult. You can, however, use […]
Making sense of test circuits with Kirchhoff’s laws: part 1
You can avoid solving simultaneous equations in multiple unknowns by identifying series and parallel combinations of resistors. When you buy test instruments, you hope they’ll have the flexibility to provide the necessary stimulus to the device under test (DUT) and acquire and process the response. Occasionally, however, you’ll need to design an external network to […]
Contending with Windows 10’s retirement: part 3
You can take several steps to ensure success when you upgrade to Windows 11. In part 1 of this series, we looked at the use of Windows to control test and measurement systems, and we considered the dilemma posed by the retirement of Windows 10 on October 14. In part 2, we looked at steps […]
How to choose analog-signal-chain components: part 5
Transimpedance and transconductance op amps convert currents to voltages and voltages to currents. We concluded part 4 of this series with a look at the instrumentation amplifier. Like the other op-amps and filter circuits we have so far described, the instrumentation amp is a voltage-input, voltage-output device. Sometimes, however, we may need a current-input voltage-output […]
How to choose analog-signal-chain components: part 4
Op amps find use in second-order filters and instrumentation amplifiers. In part 3 of this series, we described using the op amp to build some single-pole filters. Q: How do we build higher-order filters? A: Figure 1 shows one approach to a low-pass filter using the Sallen-Key topology. With two capacitors, it’s a second-order filter. […]
How to choose analog-signal-chain components: part 3
Use op amps, resistors, and capacitors to build high-pass, low-pass, and bandpass filters. In part 1 of this series, we looked at a noisy signal and discussed why it might be better to use an analog filter instead of a digital filter. Then, in part 2, we looked at the operational amplifier (op amp) and […]
Do you need a real time oscilloscope or a sampling oscilloscope?
Real-time oscilloscopes capture a signal in a single pass, while sampling oscilloscopes, sometimes called digital communication analyzers or equivalent-time sampling oscilloscopes, take multiple samples over several periods of a signal, allowing for a slower sampling rate and potentially higher resolution. Both are subcategories of digital storage oscilloscopes (DSOs). Real-time scopes are ideal for capturing one-shot events […]
